Pest categorisation of Pratylenchus loosi

Following the EFSA commodity risk assessment of Malus domestica plants imported from Türkiye into the EU, the EFSA Panel on Plant Health performed a pest categorisation of Pratylenchus loosi (Nematoda: Pratylenchidae) for the EU. Pratylenchus loosi belongs to the order Rhabditida, subfamily Pratylenchidae. This nematode is not known to be present in the EU. The species is not included in the EU Commission Implementing Regulation 2019/2072. The pest occurs primarily in tropical, subtropical and warm temperate areas. It is widely distributed in Asian countries, with tea plants (Camellia sinensis) as the main host. The pest was reported from more than 60 plant species, but reports from hosts other than C. sinensis, e.g. citrus (Citrus spp.) and banana (Musa spp.), are associated with high uncertainty due to doubtful pest identification. Morphological and molecular methods are available for the identification of the pest. Pathways of entry are host plants for planting except seeds, as well as soil attached to plants for planting, machinery or footwear. Soil import to the EU is prohibited from third countries. The climatic preferences of P. loosi are compatible with the microclimatic conditions occurring in the areas of the EU where tea is grown outside. The impact of the nematode is primarily known for Asian countries, where it is a devastating pathogen on tea plants, but there is a key uncertainty on impacts on hosts other than tea. Considering the strong pathogenicity of the pest, its establishment in tea producing areas would have negative consequences for tea producers. Therefore, the Panel concludes that P. loosi satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Plant extracts as biocontrol agents against Aspergillus carbonarius growth and ochratoxin A production in grapes

Aspergillus carbonarius (Bainier) Thom. is an important pathogen and ochratoxin A (OTA) producer in grapes that can be controlled by adopting sustainable approaches. Here we evaluate the application of natural plant extracts as an alternative to synthetic fungicides to reduce OTA contamination and to prevent infection of grapes by two isolates of A. carbonarius. In a preliminary screening, natural extracts of chestnut flower, cistus, eucalyptus, fennel, and orange peel were evaluated for their antifungal and anti-mycotoxigenic efficiency in a grape-based medium at concentrations of 10 and 20 mg/mL. Cistus and orange peel extracts demonstrated the best antifungal activity at both concentrations. Although the eucalyptus extract demonstrated no significant effect on Aspergillus vegetative growth, it significantly reduced OTA by up to 85.75 % at 10 mg/mL compared to the control. Chestnut flower, cistus, eucalyptus, and orange peel extracts were then tested at the lowest concentration (10 mg/mL) for their antifungal activity in artificially inoculated grape berries. The cistus and orange peel extracts demonstrated the greatest antifungal activity and significantly reduced mold symptoms in grapes. Moreover, all tested natural extracts were able to reduce OTA content in grape berries (17.7 ± 8.3 % - 82.3 ± 3.85 % inhibition), although not always significantly. Eucalyptus extract was particularly efficient, inhibiting OTA production by both strains of A. carbonarius by up to >80 % with no effects on fungal growth. The use of natural eucalyptus extract represents a feasible strategy to reduce OTA formation without disrupting fungal growth, apparently maintaining the natural microbial balance, while cistus and orange peel extracts appear promising as inhibitors of A. carbonarius mycelial growth. Our findings suggest that plant extracts may be useful sources of bioactive chemicals for preventing A. carbonarius contamination and OTA production. Nonetheless, it will be necessary to evaluate their effect on the organoleptic properties of the grapes.

Pest categorisation of Pestalotiopsis microspora

Following an EFSA commodity risk assessment of bonsai plants (Pinus parviflora grafted on Pinus thunbergii) imported from China, the EFSA Plant Health Panel performed a pest categorisation of Pestalotiopsis microspora, a clearly defined plant pathogenic fungus of the family Pestalotiopsidaceae. The pathogen was reported on a wide range of monocotyledonous, dicotyledonous and gymnosperms, either cultivated or wild plant species, causing various symptoms such as leaf spot, leaf blight, scabby canker, fruit spot, pre- and post-harvest fruit rot and root rot. In addition, the fungus was reported as an endophyte on a wide range of asymptomatic plant species. This pest categorisation focuses on the hosts that are relevant for the EU and for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequencing analyses. Pestalotiopsis microspora was reported in Africa, North, Central and South America, Asia and Oceania. In the EU, it was reported in the Netherlands. There is a key uncertainty on the geographical distribution of P. microspora worldwide and in the EU, because of the endophytic nature of the fungus, the lack of surveys, and because in the past, when molecular tools were not fully developed, the pathogen might have been misidentified as other Pestalotiopsis species or other members of the Pestalodiopsidaceae family based on morphology and pathogenicity tests. Pestalotiopsis microspora is not included in Commission Implementing Regulation (EU) 2019/2072. Plants for planting, fresh fruits, bark and wood of host plants as well as soil and other growing media associated with plant debris are the main pathways for the entry of the pathogen into the EU. Host availability and climate suitability in parts of the EU are favourable for the establishment and spread of the pathogen. The introduction and spread of the pathogen into the EU are expected to have an economic and environmental impact where susceptible hosts are grown. Phytosanitary measures are available to prevent the introduction and spread of the pathogen into the EU. Unless the restricted distribution in the EU is disproven, Pestalotiopsis microspora satisfies all the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Pest categorisation of Pestalotiopsis disseminata

Following the commodity risk assessments of bonsai plants from China consisting of Pinus parviflora grafted on P. thunbergii performed by EFSA, the EFSA Plant Health Panel performed a pest categorisation of Pestalotiopsis disseminata, a clearly defined plant pathogenic fungus of the family Pestalotiopsidaceae. The pathogen has been reported on herbaceous, woody and ornamental plants causing symptoms such as leaf blight, shoot blight, seedling blight, pod canker, pre- and post-harvest fruit rot, and gummosis. Moreover, the fungus was reported as an endophyte on a wide range of asymptomatic hosts. The pathogen is present in Africa, North and South America, Asia, Europe and Oceania. It has been reported from the EU, with a restricted distribution (Portugal). There is a key uncertainty on the geographical distribution of P. disseminata in the EU and worldwide, because of the endophytic nature of the fungus, the lack of surveys and since the pathogen might have been misidentified based only on morphology and pathogenicity tests. The pathogen is not included in Commission Implementing Regulation (EU) 2019/2072. This pest categorisation focuses on those hosts that are relevant for the EU and for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Plants for planting, fresh fruits, bark and wood of host plants as well as soil and other plant growing media are the main pathways for the entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the establishment of the pathogen. Despite the low aggressiveness observed in most reported hosts, and the fact that P. disseminata may colonise plants as an endophyte, its introduction and spread in the EU may have an economic and environmental impact (with a key uncertainty) where susceptible hosts are grown. Phytosanitary measures are available to prevent the introduction and spread of the pathogen. The Panel cannot conclude on whether P. disseminata satisfies all the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest, because of the key uncertainties on the restricted distribution in the EU and the magnitude of the impact.

A collection of Trichoderma isolates from natural environments in Sardinia reveals a complex virome that includes negative-sense fungal viruses with unprecedented genome organizations

Trichoderma genus includes soil-inhabiting fungi that provide important ecosystem services in their interaction with plants and other fungi, as well as biocontrol of fungal plant diseases. A collection of Trichoderma isolates from Sardinia has been previously characterized, but here we selected 113 isolates, representatives of the collection, and characterized their viral components. We carried out high-throughput sequencing of ribosome-depleted total RNA following a bioinformatics pipeline that detects virus-derived RNA-directed RNA polymerases (RdRps) and other conserved viral protein sequences. This pipeline detected seventeen viral RdRps with two of them corresponding to viruses already detected in other regions of the world and the remaining fifteen representing isolates of new putative virus species. Surprisingly, eight of them are from new negative-sense RNA viruses, a first in the genus Trichoderma. Among them is a cogu-like virus, closely related to plant-infecting viruses. Regarding the positive-sense viruses, we report the presence of an 'ormycovirus' belonging to a recently characterized group of bisegmented single-stranded RNA viruses with uncertain phylogenetic assignment. Finally, for the first time, we report a bisegmented member of Mononegavirales which infects fungi. The proteins encoded by the second genomic RNA of this virus were used to re-evaluate several viruses in the Penicillimonavirus and Plasmopamonavirus genera, here shown to be bisegmented and encoding a conserved polypeptide that has structural conservation with the nucleocapsid domain of rhabdoviruses.

Pest categorisation of Hoplolaimus galeatus

The EFSA Panel on Plant Health performed a pest categorisation of Hoplolaimus galeatus (Nematoda: Hoplolaimidae) for the EU. H. galeatus belongs to the order Rhabditida, subfamily Hoplolaiminae. This nematode is not reported from the EU and is not included in the EU Commission Implementing Regulation 2019/2072. It is widely distributed in the USA and is also reported from South America, Africa, Asia and Australia. The identity of H. galeatus is clearly defined and methods for its identification are available. H. galeatus is polyphagous and natural hosts include barley, wheat, rye, red and white clover, alfalfa, cabbage, pine, spruce, oak, apple, grapevine, as well as various ornamental plants and turf grasses. These hosts are grown over vast areas of the EU. The climate of the EU is suitable for the establishment of H. galeatus. Pathways of entry are host plants for planting except seeds, but also soil as a contaminant. Soil import to the EU is prohibited and special requirements apply to import of machinery for agricultural/forestry purposes from third countries. Impact of the nematode is best known for North American plant species. The nematode has been reported to damage cotton, maize, soybean, pine, oak and turfgrass. Many of the hosts represent a considerable economic and environmental value to the EU. Therefore, the Panel concludes that H. galeatus satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Pest categorisation of the avocado sunblotch viroid

The EFSA Panel on Plant Health conducted a pest categorisation of the avocado sunblotch viroid (ASBVd) for the EU. The identity of ASBVd, a member of the genus Avsunviroid (family Avsunviroidae) is clearly defined and detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. ASBVd has been reported in Australia, Ghana, Guatemala, Israel, Mexico, Peru, South Africa, USA (California, Florida) and Venezuela. In the EU, it has been reported in Greece (Crete Island) and Spain. The pathogen could establish in the EU wherever avocado (Persea americana) is grown. The only known natural host of ASBVd is avocado to which it causes the severe 'avocado sunblotch' disease, characterised by white, yellow, red or necrotic depressed areas or scars on the fruit surface, bleached veins and petioles of the leaf, and rectangular cracking patterns in the bark of the old branches. Fruit yield and quality are severely diminished. ASBVd infects under experimental conditions a few more species in the family Lauraceae. The viroid is naturally transmitted at an extremely high rate by seeds (up to 100% in asymptomatically infected trees), but with a low efficiency by pollen (only to the produced seeds), and possibly through root grafts. Plants for planting, including seeds, and fresh avocado fruits were identified as the most relevant pathways for further entry of ASBVd into the EU. Avocado crops are cultivated in southern EU countries. Should the pest further enter and establish in the EU, impact on the production of avocado is expected. Phytosanitary measures are available to prevent entry and spread of the viroid in the EU. ASBVd fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Pest categorisation of Coleosporium asterum, C. montanum and C. solidaginis

The EFSA Plant Health Panel performed a pest categorisation of Coleosporium asterum (Dietel) Sydow & P. Sydow, Coleosporium montanum (Arthur & F. Kern) and Coleosporium solidaginis (Schwein.) Thüm, three basidiomycete fungi belonging to the family Coleosporiaceae, causing rust diseases on Pinus spp. (aecial hosts) and on Asteraceae (telial hosts). Coleosporium asterum was described on Aster spp. in Japan and has been reported from China, Korea, France and Portugal. Coleosporium montanum is native to North America, has been introduced to Asia and has been reported from Austria on Symphyotrichum spp. Coleosporium solidaginis has been reported on Solidago spp. from North America, Asia and Europe (Switzerland and Germany). There is a key uncertainty about these reported distributions, due to the until recently accepted synonymy between these fungi and the lack of molecular studies. The pathogens are not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072, an implementing act of Regulation (EU) 2016/2031, or in any emergency plant health legislation. There are no reports of interceptions of C. asterum, C. montanum or C. solidaginis in the EU. The pathogens can further enter into, establish in and spread within the EU via host plants for planting, other than seeds and host plant parts (e.g. cut flowers, foliage, branches), other than fruits. Entry into and spread within the EU may also occur by natural means. Host availability and climate suitability in the EU are favourable for the establishment of the pathogens in areas where host plants in the Asteraceae and Pinaceae co-exist. Impacts can be expected on both aecial and telial hosts. Phytosanitary measures are available to reduce the risk of further introduction and spread of the three pathogens in the EU. Coleosporium asterum, C. montanum and C. solidaginis satisfy the criteria that are within the remit of EFSA to assess for these species to be regarded as Union quarantine pests, but a key uncertainty exists about their EU distribution.

Pest categorisation of Diplodia bulgarica

The EFSA Plant Health Panel performed a pest categorisation of Diplodia bulgarica, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects Malus domestica, M. sylvestris and Pyrus communis causing various symptoms such as canker, twig blight, gummosis, pre- and post-harvest fruit rot, dieback and tree decline. The pathogen is present in Asia (India, Iran, Türkiye) and in non-EU Europe (Serbia). Concerning the EU, the pathogen is present in Bulgaria and widespread in Germany. There is a key uncertainty on the geographical distribution of D. bulgarica worldwide and in the EU, because in the past, when molecular tools were not available, the pathogen might have been misidentified as other Diplodia species (e.g. D. intermedia, D. malorum, D. mutila, D. seriata) or other members of the Botryosphaeriaceae family affecting apple and pear based only on morphology and pathogenicity tests. Diplodia bulgarica is not included in Commission Implementing Regulation (EU) 2019/2072. Plants for planting, other than seeds, fresh fruits, and bark and wood of host plants as well as soil and other plant-growing media carrying plant debris are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors are favourable for the further establishment of the pathogen in the EU. In the areas of its present distribution, including Germany, the pathogen has a direct impact on cultivated hosts. Phytosanitary measures are available to prevent the further introduction and spread of the pathogen into the EU. Diplodia bulgarica satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Pest categorisation of Neoscytalidium dimidiatum

The EFSA Plant Health Panel performed a pest categorisation of Neoscytalidium dimidiatum, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects a wide range of woody perennial crops and ornamental plants causing symptoms such as leaf spot, shoot blight, branch dieback, canker, pre- and post-harvest fruit rot, gummosis and root rot. The pathogen is present in Africa, Asia, North and South America, and Oceania. It has also been reported from Greece, Cyprus and Italy, with a restricted distribution. Nevertheless, there is a key uncertainty on the geographical distribution of N. dimidiatum worldwide and in the EU, because in the past, when molecular tools were not available, the two synanamorphs of the pathogen (Fusicoccum-like and Scytalidium-like) might have been misidentified based only on morphology and pathogenicity tests. N. dimidiatum is not included in Commission Implementing Regulation (EU) 2019/2072. Because of the wide host range of the pathogen, this pest categorisation focuses on those hosts for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Plants for planting, fresh fruits and bark and wood of host plants as well as soil and other plant growing media are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the further establishment of the pathogen. In the areas of its present distribution, including Italy, the pathogen has a direct impact on cultivated hosts. Phytosanitary measures are available to prevent the further introduction and spread of the pathogen into the EU. N. dimidiatum satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Pest categorisation of Coleosporium eupatorii

The EFSA Plant Health Panel performed a pest categorisation of Coleosporium eupatorii Arthur ex Cummins, a clearly defined heteroecious fungus of the family Coleosporiaceae, causing rust diseases on five-needle Pinus spp. (aecial hosts) and on several genera of the Asteraceae family (telial hosts), such as Eupatorium spp. and Stevia spp. C. eupatorii is reported from Asia as well as North, Central and South America. It is not known to occur in the EU. The pathogen is not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072 and has not been intercepted in the EU. The pathogen can be detected on its host plants by DNA sequencing. The main pathway for the entry of C. eupatorii into the EU is host plants for planting, other than seeds. In the EU, there is availability of aecial host plants, with Pinus peuce, P. strobus and P. cembra being the most important ones. There is a key uncertainty about whether European Eupatorium species (specifically E. cannabinum) are hosts of C. eupatorii and thus the ability of the pathogen to complete its life cycle, establish and spread in the EU. C. eupatorii could potentially spread within the EU by both natural and human-assisted means. The introduction of C. eupatorii into the EU is expected to have an economic and environmental impact. Phytosanitary measures are available to prevent the introduction and spread of the pathogen in the EU. C. eupatorii satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Pest categorisation of Pantoea ananatis

The EFSA Plant Health Panel performed a pest categorisation of Pantoea ananatis, a Gram-negative bacterium belonging to the Erwiniaceae family. P. ananatis is a well-defined taxonomic unit; nonetheless, its pathogenic nature is not well defined and non-pathogenic populations are known to occupy several, very different environmental niches as saprophytes, or as plant growth promoting bacteria or biocontrol agents. It is also described as a clinical pathogen causing bacteraemia and sepsis or as a member of the gut microbiota of several insects. P. ananatis is the causal agent of different diseases affecting numerous crops: in particular, centre rot of onion, bacterial leaf blight and grain discoloration of rice, leaf spot disease of maize and eucalyptus blight/dieback. A few insect species have been described as vectors of P. ananatis, among them, Frankliniella fusca and Diabrotica virgifera virgifera. This bacterium is present in several countries in Europe, Africa, Asia, North and South America, and Oceania from tropical and subtropical regions to temperate areas worldwide. P. ananatis has been reported from the EU territory, both as pathogen on rice and maize and as an environmental, non-pathogenic bacterium in rice marshes and poplar rhizosoil. It is not included in EU Commission Implementing Regulation 2019/2072. The pathogen can be detected on its host plants using direct isolation, or PCR-based methods. The main pathway for the entry of the pathogen into the EU territory is host plants for planting, including seeds. In the EU, there is a large availability of host plants, with onion, maize, rice and strawberry being the most important ones. Therefore, disease outbreaks are possible almost at any latitude, except in the most northern regions. P. ananatis is not expected to have frequent or consistent impact on crop production and is not expected to have any environmental impact. Phytosanitary measures are available to mitigate the further introduction and spread of the pathogen into the EU on some hosts. The pest does not satisfy the criteria, which are within the remit for EFSA to evaluate whether the pest meets the definition of a Union quarantine pest. P. ananatis is probably widely distributed in different ecosystems in the EU. It may impact some specific hosts such as onions while on other hosts such as rice it has been reported as a seed microbiota without causing any impact and can even be beneficial to plant growth. Hence, the pathogenic nature of P. ananatis is not fully established.

Pest categorisation of Coniella granati

The EFSA Plant Health Panel performed a pest categorisation of Coniella granati, a clearly defined fungus of the Order Diaporthales and the family Schizoparmaceae, described for the first time in 1876 as Phoma granatii and later named as Pilidiella granati. The pathogen mainly affects Punica granatum (pomegranate) and Rosa spp. (rose), causing fruit rot, shoot blight and cankers on crown and branches. The pathogen is present in North America, South America, as well as in Asia, Africa, Oceania and Eastern Europe and has also been reported in the EU (Greece, Hungary, Italy and Spain), where it is widespread in the major pomegranate growing areas. Coniella granati is not included in Commission Implementing Regulation (EU) 2019/2072 and there are no interceptions in the EU. This pest categorisation focused on those hosts for which the pathogen was detected and formally identified in natural conditions. Plants for planting, fresh fruits and as well as soil and other plant growing media are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the further establishment of the pathogen. In the area of its present distribution, including Italy and Spain, the pathogen has a direct impact in pomegranate orchards as well as during post-harvest storage. Phytosanitary measures are available to prevent the further introduction and spread of the pathogen into the EU. Coniella granati does not satisfy the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest as it is present in several EU MSs.

Improved YOLOX-Tiny network for detection of tobacco brown spot disease

INTRODUCTION

Tobacco brown spot disease caused by Alternaria fungal species is a major threat to tobacco growth and yield. Thus, accurate and rapid detection of tobacco brown spot disease is vital for disease prevention and chemical pesticide inputs.

METHODS

Here, we propose an improved YOLOX-Tiny network, named YOLO-Tobacco, for the detection of tobacco brown spot disease under open-field scenarios. Aiming to excavate valuable disease features and enhance the integration of different levels of features, thereby improving the ability to detect dense disease spots at different scales, we introduced hierarchical mixed-scale units (HMUs) in the neck network for information interaction and feature refinement between channels. Furthermore, in order to enhance the detection of small disease spots and the robustness of the network, we also introduced convolutional block attention modules (CBAMs) into the neck network.

RESULTS

As a result, the YOLO-Tobacco network achieved an average precision (AP) of 80.56% on the test set. The AP was 3.22%, 8.99%, and 12.03% higher than that obtained by the classic lightweight detection networks YOLOX-Tiny network, YOLOv5-S network, and YOLOv4-Tiny network, respectively. In addition, the YOLO-Tobacco network also had a fast detection speed of 69 frames per second (FPS).

DISCUSSION

Therefore, the YOLO-Tobacco network satisfies both the advantages of high detection accuracy and fast detection speed. It will likely have a positive impact on early monitoring, disease control, and quality assessment in diseased tobacco plants.

Plant Growth Promotion and Biocontrol of Leaf Blight Caused by Nigrospora sphaerica on Passion Fruit by Endophytic Bacillus subtilis Strain GUCC4

Passion fruit (Passiflora edulis Sims) is widely cultivated in tropic and sub-tropic regions for the production of fruit, flowers, cosmetics, and for pharmacological applications. Its high economic, nutritional, and medical values elicit the market demand, and the growing areas are rapidly increasing. Leaf blight caused by Nigrospora sphaerica is a new and emerging disease of passion fruit in Guizhou, in southwest China, where the unique karst mountainous landscape and climate conditions are considered potential areas of expansion for passion fruit production. Bacillus species are the most common biocontrol and plant-growth-promotion bacteria (PGPB) resources in agricultural systems. However, little is known about the endophytic existence of Bacillus spp. in the passion fruit phyllosphere as well as their potential as biocontrol agents and PGPB. In this study, 44 endophytic strains were isolated from 15 healthy passion fruit leaves, obtained from Guangxi province, China. Through purification and molecular identification, 42 of the isolates were ascribed to Bacillus species. Their inhibitory activity against N. sphaerica was tested in vitro. Eleven endophytic Bacillus spp. strains inhibited the pathogen by >65%. All of them produced biocontrol- and plant-growth-promotion-related metabolites, including indole-3-acetic acid (IAA), protease, cellulase, phosphatase, and solubilized phosphate. Furthermore, the plant growth promotion traits of the above 11 endophytic Bacillus strains were tested on passion fruit seedlings. One isolate, coded B. subtilis GUCC4, significantly increased passion fruit stem diameter, plant height, leaf length, leaf surface, fresh weight, and dry weight. In addition, B. subtilis GUCC4 reduced the proline content, which indicated its potential to positively regulate passion fruit biochemical properties and resulted in plant growth promotion effects. Finally, the biocontrol efficiencies of B. subtilis GUCC4 against N. sphaerica were determined in vivo under greenhouse conditions. Similarly to the fungicide mancozeb and to a commercial B. subtilis-based biofungicide, B. subtilis GUCC4 significantly reduced disease severity. These results suggest that B. subtilis GUCC4 has great potential as a biological control agent and as PGPB on passion fruit.

Pest categorisation of Xylella taiwanensis

The EFSA Plant Health Panel performed a pest categorisation of Xylella taiwanensis, a Gram-negative bacterium belonging to the Xanthomonadaceae. The pathogen is a well-defined taxonomic entity, and it is the causal agent of the pear leaf scorch. X. taiwanensis is present in subtropical and temperate areas of the island of Taiwan, where it affects low chilling pear cultivars of the species Pyrus pyrifolia (Asian pear). No other plant species are reported to be affected by the pathogen. The pathogen is not known to be present in the EU territory and it is not included in the Commission Implementing Regulation (EU) 2019/2072. The main pathway for the entry of the pathogen into the EU territory is host plants for planting (except seeds); another possible pathway might be represented by putative insect vectors, though their identity remains unknown. The cultivated area of P. pyrifolia in the EU territory is very limited. Conversely, the genetically related P. communis is widely cultivated in most EU Member States and there is no information so far on the susceptibility of its several cultivars. Should the pest establish in the EU, economic impact is expected, provided that suitable insect vectors are present and P. communis is as susceptible to infection as P. pyrifolia. Phytosanitary measures are available to prevent the introduction and spread of the pathogen into the EU, since plants for planting from Taiwan is a closed pathway; nonetheless, putative vectors, if confirmed and identified, may represent an additional risk of the pathogen's introduction and spread. The lack of knowledge on whether X. taiwanensis can infect P. communis, the identity and presence of suitable vectors in the EU lead to key uncertainties on entry, establishment, spread and impact. X. taiwanensis satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Pest categorisation of Lasiodiplodia pseudotheobromae

The EFSA Plant Health Panel performed a pest categorisation of Lasiodiplodia pseudotheobromae, a clearly defined fungus of the family Botryosphaeriaceae, which was first described in 2008 as a cryptic species within the L. theobromae complex. The pathogen affects a wide range of woody perennial crops and ornamental plants causing root rot, damping-off, leaf spots, twig blight, cankers, stem-end rot, gummosis, branch dieback and pre- and post-harvest fruit rots. Lasiodiplodia pseudotheobromae is present in Africa, Asia, North and South America and Oceania and has also been reported from Spain with a restricted distribution. However, there is uncertainty on the status of the pathogen worldwide and in the EU because in the past, when molecular tools (particularly multigene phylogenetic analysis) were not available, the pathogen might have been misidentified as L. theobromae. Lasiodiplodia pseudotheobromae is not included in Commission Implementing Regulation (EU) 2019/2072 and there are no interceptions in the EU. Because of the very wide host range of the pathogen, this pest categorisation focused on those hosts for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Plants for planting, including seeds, fresh fruits and bark and wood of host plants as well as soil and other plant-growing media are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the further establishment of the pathogen. In the area of its present distribution, including Spain, the pathogen has a direct impact on cultivated hosts. multilocus measures are available to prevent the further introduction and spread of the pathogen into the EU. Lasiodiplodia pseudotheobromae satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Pest categorisation of Coleosporium phellodendri

The EFSA Plant Health Panel performed a pest categorisation of Coleosporium phellodendri Kom., a basidiomycete fungus belonging to the order Pucciniales, causing rust diseases on Pinus spp. (aecial host) and on Phellodendron spp. (telial host). C. phellodendri has been reported only from Asia (namely, China, Republic of Korea, Japan and Russia) and is not known to be present in the EU territory. The pathogen is not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072, an implementing act of Regulation (EU) 2016/2031, or in any emergency plant health legislation. The pathogen could enter into, become established in, and spread within the EU territory via host plants for planting and host plant parts (e.g. foliage, branches) other than seeds and fruits, respectively. Spread within the EU territory may also occur by natural means if Phellodendron spp. were present. Availability of the Pinus spp. and climate suitability factors occurring in the EU are favourable for the establishment of the pathogen in areas where Phellodendron spp. are also present. Phytosanitary measures are available to prevent the introduction and spread of the pathogen in the EU. C. phellodendri does not satisfy all the criteria assessed by EFSA for consideration as a Union quarantine pest as no economic and environmental impact of this pathogen is expected without widespread presence of Phellodendron spp. in the EU.

Pest categorisation of chickpea chlorotic dwarf virus

The EFSA Panel on Plant Health conducted a pest categorisation of chickpea chlorotic dwarf virus (CpCDV) for the EU territory. The identity of CpCDV, a member of the genus Mastrevirus (family Geminiviridae) is established. Reliable detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. CpCDV has been reported in Africa, Asia and Oceania. It has not been reported in the EU. CpCDV infects plant species in the family Fabaceae and several species of other families (Amaranthaceae, Brassicaceae, Caricaceae, Cucurbitaceae, Malvaceae and Solanaceae), including weeds. It may induce symptoms on its hosts, causing severe yield reduction. The virus is transmitted in a persistent, circulative and non‐propagative manner by the leafhopper species Orosius orientalis and O. albicinctus, which are not regulated. O. orientalis is known to be present in some EU member states. Plants for planting (other than seeds), parts of plants and cut flowers of CpCDV hosts and viruliferous leafhoppers were identified as the most relevant pathways for the entry of CpCDV into the EU. Cultivated and wild hosts of CpCDV are distributed across the EU. Would the pest enter and establish in the EU territory, impact on the production of cultivated hosts is expected. Phytosanitary measures are available to prevent entry and spread of the virus in the EU. CpCDV fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Pest categorisation of Stenocarpella maydis

The EFSA Plant Health Panel performed a pest categorisation of Stenocarpella maydis, a clearly defined fungus causing seedling blight, stalk and ear rot in maize, its only confirmed main host. The pathogen occurs in many countries of North, Central and South America, Africa, Asia and Oceania where maize is grown commercially. It is present in the EU with restricted distribution (Czech Republic and Spain). Stenocarpella maydis is not included in Commission Implementing Regulation (EU) 2019/2072. Plants for planting (maize seeds) is the main pathway of entry and spread in the EU. Host availability and climate are favourable for the establishment of the pathogen in maize-growing areas of the EU. The pathogen has a direct impact on yield and quality of maize production. Phytosanitary measures are available to mitigate further introduction and spread of the pathogen into the EU. The Panel concludes that S. maydis satisfies all the criteria to be regarded as a potential Union quarantine pest.

Biological characterization and in vitro fungicide screenings of a new causal agent of wheat Fusarium head blight in Tibet, China

Wheat (Triticum aestivum L.) is an important cereal crop, widely grown throughout the temperate zones, and also suitable for cultivation at higher elevations. Fusarium head blight (FHB) is a highly destructive disease of wheat throughout the globe. In July 2020, serious wheat FHB symptoms were observed in open fields located in Linzhi City, southeast of Tibet, China. The causal agent was identified as Fusarium avenaceum (Fr.) Sacc. by amplification and sequencing of the internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (EF-1α) gene, and RNA polymerase II subunit (RPB-2) gene, as well as by morphological characterization. Koch’s postulates were confirmed by a pathogenicity test on healthy spikes, including re-isolation and identification. To our knowledge, this is the first report of F. avenaceum causing FHB on wheat in Tibet, China. Moreover, to determine pathogen characteristics that may be useful for future disease management, the utilization of different carbon and nitrogen resources, temperature, light, and ultraviolet (UV) irradiation on mycelium growth and conidia germination were studied. Soluble starch and peptone were the best carbon, and nitrogen source for the pathogen respectively. The optimal temperatures for the pathogen’s mycelium growth and conidia germination were 15–20°C, matching the average temperature during the growing season in Linzhi (Tibet). Meanwhile, alternating 8-h light and 16-h dark was shown to be conducive to mycelia growth, and complete darkness facilitated conidia germination. In addition, UV Irradiation of 48 MJ/cm², approximately 100 times of the local condition, did not inhibit the germination of conidia. Furthermore, in vitro screening of effective fungicides was conducted. Among the seven tested pesticides, carbendazim showed the best inhibition rate, with an EC₅₀ (concentration for 50% of maximal effect) value of 2.1 mg/L. Propiconazole also showed sufficient inhibitory effects against F. avenaceum, with an EC₅₀ value of 2.6 mg/L. The study provides insights into the newly identified causal agent of wheat FHB in Tibet, China, as well as first pathogen characteristics and promising candidate substances for its management.

Pest categorisation of Colletotrichum aenigma, C. alienum, C. perseae, C. siamense and C. theobromicola

The EFSA Plant Health Panel performed a pest categorisation of Colletotrichum aenigma, C. alienum, C. perseae, C. siamense and C. theobromicola, five clearly defined fungi of the C. gloeosporioides complex causing anthracnose. The pathogens are widely distributed in at least three continents. C. aenigma and C. siamense are reported from Italy and C. alienum from Portugal, including the Madeira Islands, with a restricted distribution. C. perseae and C. theobromicola are not known to be present in the EU. However, there is uncertainty on the status of the pathogens worldwide and in the EU because of the taxonomic re-evaluation of the genus Colletotrichum and the lack of specific surveys. The pathogens are not included in Commission Implementing Regulation (EU) 2019/2072 and there are no reports of interceptions in the EU. With the exception of C. perseae, which has a very limited number of hosts, the other four Colletotrichum species have relatively wide host ranges. Therefore, this pest categorisation focused on those hosts for which there is robust evidence that the pathogens were formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Host plants for planting and fresh fruits are the main entry pathways into the EU. Host availability and climate suitability factors occurring in some parts of the EU are favourable for the establishment of the pathogens. No yield losses have been reported so far in the EU but in non-EU areas of their current distribution, the pathogens have a direct impact on cultivated hosts that are also relevant for the EU. Phytosanitary measures are available to prevent the further introduction and spread of C. aenigma, C. alienum and C. siamense into the EU as well as the introduction and spread of C. perseae and C. theobromicola. C. aenigma, C. alienum, C. perseae, C. siamense and C. theobromicola satisfy the criteria that are within the remit of EFSA to assess for these species to be regarded as potential Union quarantine pests.

Pest categorisation of Atalodera andina

The EFSA Panel on Plant Health performed a pest categorisation of Atalodera andina (Nematoda: Heteroderidae) for the European Union (EU) territory. A. andina belongs to the order Rhabditida, subfamily Ataloderinae. This species has not been reported from the EU. It is not included in the EU Commission Implementing Regulation 2019/2072. It is present in the area of the Lake Titicaca of both Peru and Bolivia and in valleys of the region. There is a report in literature stating that specimens were obtained from Chile and identified as A. andina but details on their geographical origin were not given. The identity of A. andina is well established and methods of its identification are available. Natural hosts include the tuber crops Ullucus tuberosus, Oxalis tuberosa and the Andean potato (Solanum tuberosum subsp. andigenum). Experimental hosts include plants of the genus Brassica (such as B. oleracea, B. napus, B. campestris), sugar beet, tomato and clover. Pathways of entry are host plants for planting including seed tubers, subterranean parts of plants intended for consumption, soil as such or attached to plants for planting, machinery or footwear, soil in packaging (bags). Suitable climates exist in the EU but their extent is uncertain and depends on assumptions made on the occurrence of the pest around Lake Titicaca. In the EU, potato, which is grown on about 1,500,000 ha annually, is expected to be the main host of the nematode. Soil and plants for planting are prohibited from import to the EU from third countries where the pest is known to occur. However, this does not cover hosts of A. andina other than species of Solanaceae. The nematode has been reported to damage Andean potato crops, although this has not been quantified. Following its introduction in the EU, A. andina is expected to cause impacts on potato (S. tuberosum subsp. tuberosum), although there is uncertainty on the magnitude of this impact. Also damage on other hosts cannot be excluded. Therefore, the Panel concludes that A. andina satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Pest categorisation of Capsicum chlorosis virus

The EFSA Panel on Plant Health conducted a pest categorisation of Capsicum chlorosis virus (CaCV) for the EU territory. The identity of CaCV, a member of the genus Orthotospovirus (family Tospoviridae), is established and reliable detection and identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. CaCV has been reported in Australia, China, India, Iran, Taiwan, Thailand and USA (Hawaii). In the EU, it has been reported once in Greece (Crete Island). The NPPO of Greece reported that CaCV is no longer present in Greece. CaCV infects plant species in the family Solanaceae (i.e. pepper, tomato) and several species of other families, including ornamentals. It may induce severe symptoms on its hosts, mainly on leaves and fruits, which may become unmarketable. The virus is transmitted in a persistent propagative mode by the thrips Ceratothripoides claratris, Frankliniella schultzei, Microcephalothrips abdominalis and Thrips palmi. C. claratris and T. palmi are EU quarantine pests. M. abdominalis is known to be present in several EU member states and it is not regulated in the EU. Plants for planting, parts of plants, fruits and cut flowers of CaCV hosts, and viruliferous thrips were identified as the most relevant pathways for the entry of CaCV into the EU. Cultivated and wild hosts of CaCV are distributed across the EU. Should the pest enter and establish in the EU territory, impact on the production of cultivated hosts is expected. Phytosanitary measures are available to prevent entry and spread of the virus in the EU. CaCV fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Pest categorisation of Fusarium pseudograminearum

The EFSA Plant Health Panel performed a pest categorisation of Fusarium pseudograminearum O'Donnell & T. Aoki. F. pseudograminearum is a soil-borne fungal pathogen, able to cause a disease known as Fusarium crown rot (FCR, also known as foot and root rot) and occasionally Fusarium head blight on small grain cereals, particularly Triticum aestivum L., Triticum turgidum L. spp. durum (Dest.), Hordeum vulgare L. and triticale (xTriticosecale). In addition, F. pseudograminearum has been isolated from soybean (Glycine max L.) and from some grass genera, such as Phalaris, Agropyron and Bromus, which represent potentially important inoculum reservoirs. This pathogen has been reported in arid and semi-arid cropping regions in Australia, New Zealand, North and South America, northern Africa and South Africa, the Middle East and Asia. In the EU, it has been reported in Italy since 1994 and later in Spain on field-grown durum wheat, but uncertainty remains regarding the actual distribution of the pathogen in the EU. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. Seeds of host plants and soil and other substrates are the main pathways for the entry and spread of the pathogen into the EU. There are no reports of interceptions of F. pseudograminearum in the EU. Host availability and climate suitability occurring in the EU favour establishment of the pathogen and allow it to establish in areas from which it has not been reported. Phytosanitary measures are available to prevent the introduction of the pathogen into the EU, and additional measures are available to mitigate the risk of spread. In the non-EU areas of its present distribution, the pathogen has a direct impact on cultivated hosts (e.g. wheat, barley, triticale and soybean) that are also relevant for the EU. However, no crop losses have been reported so far in the EU. The Panel concludes that F. pseudograminearum satisfies all the criteria to be regarded as a potential Union quarantine pest.

Pest categorisation of High Plains wheat mosaic virus

The EFSA Panel on Plant Health conducted a pest categorisation of High Plains wheat mosaic virus (HPWMoV) for the EU territory. The identity of HPWMoV, a member of the genus Emaravirus (family Fimoviridae), is well established and reliable identification methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. HPWMoV has been reported from Argentina, Australia, Canada, Ukraine and USA, and it is not known to be present in the EU. HPWMoV infects plant species of the family Poaceae (i.e. wheat, maize and several other cultivated or wild Poaceae species). It is the causal agent of High Plains disease of wheat and maize, inducing symptoms ranging from mild to severe mosaic, chlorosis and necrosis in wheat, and chlorotic streaks in maize plants. The virus is transmitted by the wheat curl mite Aceria tosichella, which is present in the EU. HPWMoV transmission via seeds was reported to occur in sweet corn. Sweet corn seeds for sowing were identified as the most relevant pathway for entry of HPWMoV into the EU. Seeds from other hosts and viruliferous wheat curl mites were identified as entry pathways associated with uncertainties. Machinery not appropriately cleaned may move infected seeds and/or parts of cereals infested by viruliferous mites. Cultivated and wild hosts of HPWMoV are distributed across the EU. Would the pest enter and establish in the EU territory, economic impact on the production of cultivated hosts is expected. Phytosanitary measures are available to prevent entry and spread of the virus in the EU. HPWMoV fulfils the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Efficacy and economics evaluation of seed rhizome treatment combined with preplant soil fumigation on ginger soilborne disease, plant growth, and yield promotion

BACKGROUND

Ginger (Zingiber officinale Roscoe) is widely planted around the world. Owing to continuous planting, ginger is seriously affected by soilborne fungi, bacteria, and nematodes. Although preplant soil fumigation is an effective prevention strategy of soilborne diseases, individual fumigant and technology could not provide effective control of ginger soilborne disease. In our research, different combinations of soil fumigants and seed rhizome treatments were evaluated by monitoring the soil pathogens population, ginger growth, yield, and estimation of economic benefits.

RESULTS

Soil fumigation effectively reduced the population of soilborne pathogens, and chloropicrin had a better control effect on soilborne pathogens than dazomet did. Preplant soil fumigation and seed rhizome treatment not only provide good control of soilborne disease, but also reduced the incidence of plant foliar pest and disease. Average yield increase rate of seed rhizome treatment was 12.0%; the highest yield increase was 24.4%. The average cost of seed rhizome treatment only increased by about 2.86%, but the rate of net revenue increase for the seed rhizome treatment reached up to 19.1%.

CONCLUSION

Seed rhizome treatment is a very cost-effective soilborne disease control technology. In the management of soilborne diseases, the combined application of soil fumigation and seed rhizome treatment can reduce the risk of crops infected by soilborne diseases and ensure high and stable crop yields. © 2021 Society of Chemical Industry.

Pest categorisation of Plicosepalus acaciae

The EFSA Panel on Plant Health performed a pest categorisation of Plicosepalus acaciae (Zuccarini) Wiens & Polhill), the acacia strap flower, a hemiparasitic plant of the family Loranthaceae parasitising woody plants. Host plants include several species of the genera Vachellia, Tamarix and Ziziphus and various fruit crops. P. acaciae is present in the Middle East and Eastern Africa and is not known to occur in the EU. P. acaciae has a long flowering period of about 10 months, from June to April the following year, during which flowers are pollinated by insects and birds. P. acaciae produces single seeded red berries that are eaten by birds, which then disseminate the seeds. The only known bird observed to disseminate the seeds of P. acaciae is Pycnonotus xanthopygos, which has been recorded just once (Spain) but it is not established in the EU. P. acaciae could enter into the EU with host plants for planting. Host plants are present and suitable climatic conditions occur in parts of the EU. If a suitable bird would adapt to transfer the seeds, establishment and spread of P. acaciae within the EU would be possible. If P. acaciae would be able to establish and spread, impacts on some crop plants (e.g. Juglans regia, Ficus carica, Punica granatum, Pistacia vera), ornamental plants, as well as native vegetation could occur. P. acaciae fulfils the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest. Uncertainty remains on bird species other than P. xanthopygos transferring P. acaciae, the magnitude of potential impacts and the host range.

Bioprospecting Phenols as Inhibitors of Trichothecene-Producing Fusarium: Sustainable Approaches to the Management of Wheat Pathogens

Fusarium spp. are ubiquitous fungi able to cause Fusarium head blight and Fusarium foot and root rot on wheat. Among relevant pathogenic species, Fusarium graminearum and Fusarium culmorum cause significant yield and quality loss and result in contamination of the grain with mycotoxins, mainly type B trichothecenes, which are a major health concern for humans and animals. Phenolic compounds of natural origin are being increasingly explored as fungicides on those pathogens. This review summarizes recent research activities related to the antifungal and anti-mycotoxigenic activity of natural phenolic compounds against Fusarium, including studies into the mechanisms of action of major exogenous phenolic inhibitors, their structure-activity interaction, and the combined effect of these compounds with other natural products or with conventional fungicides in mycotoxin modulation. The role of high-throughput analysis tools to decipher key signaling molecules able to modulate the production of mycotoxins and the development of sustainable formulations enhancing potential inhibitors’ efficacy are also discussed.

Pest categorisation of Apium virus Y

Following a request from the EU Commission, the EFSA Panel on Plant Health conducted a pest categorisation of Apium virus Y (ApVY) for the EU territory. The identity of the ApVY, a member of the genus Potyvirus (family Potyviridae), is well established and reliable detection methods are available. The pathogen is not included in EU Commission Implementing Regulation 2019/2072. ApVY, considered endemic in Australia, was reported also in New Zealand and USA. In the EU, the virus was identified in Germany and Slovenia. No information on adoption of official control measures is available. In natural conditions, ApVY infects plant species of the family Apiaceae (i.e. celery, coriander, dill, parsley, bishop's weed) in which it generally induces leaf symptoms and/or stunting. In some hosts (i.e. parsley and poison hemlock), ApVY may be asymptomatic. The virus is transmitted in a non-persistent manner by the aphid Myzus persicae which is widespread in the EU. Although ApVY transmission through seeds has been experimentally excluded for some hosts (i.e. poison hemlock and celery), uncertainty exists for the other hosts because seed transmission is not uncommon for potyvirids. Plants for planting, including seeds for sowing, were identified as potential pathways for entry of ApVY into the EU. Cultivated and wild hosts of ApVY are distributed across the EU. Economic impact on the production of the cultivated hosts is expected if further entry and spread in the EU occur. Phytosanitary measures are available to prevent further entry and spread of the virus. Currently, ApVY does not fulfil the criterion of being absent or present with restricted distribution and under official control to be regarded as a potential Union quarantine, unless official control is implemented. This conclusion is associated with high uncertainty regarding the current virus distribution in the EU.

Pest categorisation of Fusarium oxysporum f. sp. cubense Tropical Race 4

The EFSA Plant Health Panel performed a pest categorisation of Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), an ascomycete fungus causing Fusarium wilt (Panama disease) on Musa spp. Foc TR4 is pathogenic to the commercial banana varieties including those of the 'Cavendish' group and is considered as the most destructive among Foc haplotypes. Uncertainty exists on the host range of Foc TR4, since it has not been demonstrated whether it can infect plant species other than Musa spp., which were previously reported as hosts of other Foc races. Foc TR4 is morphologically and physiologically identical to other representatives of the Fusarium oxysporum Species Complex (FOSC), but all Foc TR4 isolates belong to a single clonal lineage within the vegetative compatibility groups 01213-01216. Several PCR protocols are described in the literature, but their specificity has been questioned as they may generate false positives. The pathogen is not included in EU Commission Implementing Regulation 2019/2072 and is not reported as present in the EU territory. Several potential entry pathways and means of spread were identified, including host plants for planting other than vitroplants, fresh fruits and leaves of host plants, soil and other substrates originating in infested third countries. Host availability and climate suitability occurring in some areas of the EU are favourable for the establishment of Foc TR4. Being a soil-borne pathogen, eradication of Foc TR4 once it enters a new area is very difficult. Therefore, effective quarantine measures are essential in pathogen-free areas. Although not specifically targeting against Foc TR4, phytosanitary measures are currently available to prevent the introduction of the pathogen into the EU. Considering that banana-growing EU countries account for over 12% of the EU banana supply, it is expected that the economic impact of Foc TR4 on the European banana production areas would be devastating. Foc TR4 satisfies the criteria that are within the remit of EFSA to assess for this pathogen to be regarded as a potential Union quarantine pest.

Pest categorisation of Xanthomonas citri pv. viticola

The EFSA Plant Health Panel performed a pest categorisation of Xanthomonas citri pv. viticola (Nayudu) Dye, a Gram-negative bacterium belonging to the Xanthomonadaceae family. The pathogen is a well-defined taxonomic unit and is the causal agent of the leaf spot and bacterial canker of Vitis vinifera. This bacterium is present in India and Brazil, where it affects table grape cultivation; the same pathogen is able to cause a disease on Azadirachta indica and on some weed species. Reports indicate that the bacterium is present in Thailand as well. The pathogen has never been reported from the EU territory and it is not included in EU Commission Implementing Regulation 2019/2072. The pathogen can be detected on its host plants using direct isolation, serological or PCR-based methods. Its identification is achieved using biochemical and nutritional assays, together with a multilocus sequence analysis based on seven housekeeping genes. The main pathway for the entry of the pathogen into the EU territory is plant propagation material. In the EU, there is large availability of host plants, with grapevine being one of the most important crops in Europe and more specifically in its Mediterranean areas. Since X. citri pv. viticola is only reported in tropical and subtropical areas (BSh and Aw climatic zones according to the Köppen-Geiger classification), there is uncertainty whether the climatic conditions in the EU territory are suitable for its establishment. Nevertheless, due to the great importance of grapevine for the EU agriculture, any disease outbreak may have a high-economic impact. Phytosanitary measures are available to prevent the introduction of the pathogen into the EU. X. citri pv. viticola satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Pest categorisation of carrot thin leaf virus

Following a request from the EU Commission, the EFSA Panel on Plant Health conducted a pest categorisation of carrot thin leaf virus (CTLV) for the EU territory. The identity of CTLV, a member of the genus Potyvirus (family Potyviridae), is well established and reliable detection methods are available. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. CTLV has been reported from the USA and Colombia. In the EU, the virus was reported in Germany and Slovenia and the NPPO of both countries confirmed these reports. No official national measures have been taken so far. In 2018, CTLV was reported from Greece on Torilis arvensis subsp. arvensis. Since then, no other reports exist. According to the NPPO, the virus did not establish in Greece. In natural conditions, CTLV infects plant species of the family Apiaceae (i.e., carrot, coriander, parsley and several wild weed species). The virus is transmitted in a non-persistent manner by the aphids Myzus persicae and Cavariella aegopodii, which are widely distributed in the EU. CTLV has been reported not to be transmitted by carrot seeds, while no information is available for the other hosts. Since transmission through seeds is not uncommon for potyvirids, it cannot be excluded that CTLV can be seed transmitted for some hosts. Plants for planting, including seeds for sowing, were identified as potential pathways for entry of CTLV into the EU. Cultivated and wild hosts of CTLV are distributed across the EU. Economic impact on the production of cultivated hosts is expected if further entry and spread in the EU occur. Phytosanitary measures are available to prevent further entry and spread of the virus on its cultivated hosts. Currently, CTLV does not fulfil the criterion of being absent or present with restricted distribution and under official control to be regarded as a potential Union quarantine pest, unless official control is implemented. This conclusion is associated with high uncertainty regarding the current virus distribution in the EU.

Pest categorisation of Colletotrichum plurivorum

The EFSA Plant Health Panel performed a pest categorisation of Colletotrichum plurivorum Damm, Alizadeh & Toy. Sato, a well-defined fungus of the C. orchidearum species complex which has been reported from Africa, Asia and America to cause anthracnose and pre- and post-harvest fruit rots on more than 30 plant genera. The pathogen has not been reported from the EU territory and is not included in EU Commission Implementing Regulation 2019/2072. Because of the very wide host range, this pest categorisation focused on Abelmoschus esculentus, Capsicum spp., Carica papaya, Glycine max, Manihot esculenta, Phaseolus lunatus, Pyrus bretschneideri and Vitis spp. for which there was robust evidence that C. plurivorum was formally identified by morphology and multilocus gene sequencing analysis. Host plants for planting and fresh fruits are the main pathways for the entry of the pathogen into the EU. The host availability and climate suitability factors occurring in some parts of the EU are favourable for the establishment of the pathogen. Economic impact on the production of the main hosts is expected if establishment occurs. Phytosanitary measures are available to prevent the introduction of the pathogen into the EU. Colletotrichum plurivorum satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest. However, there is a high uncertainty on the status of C. plurivorum in the EU territory because of the lack of specific surveys following the re-evaluation of the taxonomy of the genus Colletotrichum.

Pest categorisation of Fusarium brachygibbosum

The EFSA Plant Health Panel performed a pest categorisation of Fusarium brachygibbosum Padwick. F. brachygibbosum is a well-characterised fungal plant pathogen with opportunistic behaviour, mostly isolated along with other fungal pathogens in symptomatic hosts. It has been reported from Africa, America, Asia and Oceania where it is has been associated with a wide range of symptoms on approximately 25 cultivated and non-cultivated plant species. The pathogen has been reported in Italy in soil/marine sediments and in quinoa (Chenopodium quinoa) and durum wheat (Triticum turgidum subsp. durum) seeds. The pathogen is not included in the EU Commission Implementing Regulation 2019/2072. This pest categorisation focused on a selected range of host plant species on which F. brachygibbosum fulfilled Koch's postulates and was formally identified by multilocus gene sequencing analysis. Host plants for planting, seed of host plants and soil and other substrates originating in infested third countries are main pathways for the entry of the pathogen into the EU. There are no reports of interceptions of F. brachygibbosum in the EU. Host availability and climate suitability factors occurring in the EU are favourable for the establishment of the pathogen in Member States (MSs). Phytosanitary measures are available to prevent the introduction of the pathogen into the EU. Additional measures are available to mitigate the risk of entry and spread of the pathogen in the EU. Despite the low aggressiveness observed in some reported hosts, it has been shown that, in the areas of its present distribution, the pathogen has a direct impact on certain hosts (e.g. almond, onion, soybean, tobacco) that are also relevant for the EU. The Panel concludes that F. brachygibbosum satisfies all the criteria to be regarded as a potential Union quarantine pest. However, high uncertainty remains regarding the distribution of the pathogen in the EU and some uncertainty exists about its potential impact in the EU. Specific surveys and re-evaluation of Fusarium isolates in culture collections could reduce these uncertainties.

Molecular Docking and Comparative Inhibitory Efficacy of Naturally Occurring Compounds on Vegetative Growth and Deoxynivalenol Biosynthesis in Fusarium culmorum

The fungal pathogen Fusarium culmorum causes Fusarium head blight in cereals, resulting in yield loss and contamination of the grain by type B trichothecene mycotoxins such as deoxynivalenol (DON), and its acetylated derivatives. Synthesis of trichothecenes is driven by a trichodiene synthase (TRI5) that converts farnesyl pyrophosphate (FPP) to trichodiene. In this work, 15 naturally occurring compounds that belong to the structural phenol and hydroxylated biphenyl classes were tested in vitro and in planta (durum wheat) to determine their inhibitory activity towards TRI5. In vitro analysis highlighted the fungicidal effect of these compounds when applied at 0.25 mM. Greenhouse assays showed a strong inhibitory activity of octyl gallate 5, honokiol 13 and the combination propyl gallate 4 + thymol 7 on trichothecene biosynthesis. Docking analyses were run on the 3D model of F. culmorum TRI5 containing the inorganic pyrophosphate (PPi) or FPP. Significant ligand affinities with TRI-PPi and TRI-FPP were observed for the same sites for almost all compounds, with 1 and 2 as privileged sites. Octyl gallate 5 and honokiol 13 interacted almost exclusively with sites 1 and 2, by concurrently activating strong H-bonds with common sets of amino acids. These results open new perspectives for the targeted search of naturally occurring compounds that may find practical application in the eco-friendly control of FHB in wheat.

Pest categorisation of Colletotrichum fructicola

The EFSA Plant Health Panel performed a pest categorisation of Colletotrichum fructicola Prihast., a well-defined polyphagous fungus of the C. gloeosporioides complex which has been reported from all the five continents to cause anthracnose, bitter rot and leaf spotting diseases on over 90 cultivated and non-cultivated woody or herbaceous plant species. The pathogen is not included in EU Commission Implementing Regulation 2019/2072. Because of the very wide host range, this pest categorisation focused on Camellia sinensis, Citrus sinensis, C. reticulata, Fragaria × ananassa, Malus domestica, M. pumila, Persea americana, Prunus persica, Pyrus pyrifolia and P. bretschneideri for which there was robust evidence that C. fructicola was formally identified by morphology and multilocus gene sequencing analysis. Host plants for planting and fresh fruits are the main pathways for the entry of the pathogen into the EU. There are no reports of interceptions of C. fructicola in the EU. The pathogen has been reported from Italy and France. The host availability and climate suitability factors occurring in some parts of the EU are favourable for the establishment of the pathogen. Economic impact on the production of the main hosts is expected if establishment occurs. Phytosanitary measures are available to prevent the re-introduction of the pathogen into the EU. Although the pathogen is present in the EU, there is a high uncertainty on its actual distribution in the territory because of the re-evaluation of Colletotrichum taxonomy and the lack of systematic surveys. Therefore, the Panel cannot conclude with certainty on whether C. fructicola satisfies the criterium of being present but not widely distributed in the EU to be regarded as a potential Union quarantine pest unless systematic surveys for C. fructicola are conducted and Colletotrichum isolates from the EU in culture collections are re-evaluated.

Phylogenomic Analysis of a 55.1-kb 19-Gene Dataset Resolves a Monophyletic Fusarium that Includes the Fusarium solani Species Complex

Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option available.

Water distribution systems in Sardinian hospitals host invasive clonal lineages of the Fusarium oxysporum and Fusarium solani species complexes

Several Fusarium species cause disease on human hosts, including commonly fatal infections in immunocompromised individuals. Recently, cases of hospitalized patients affected by fusaria were reported in the Tyrrhenian Island of Sardinia, Italy. To precisely characterize the Fusarium species and haplotypes present in hospitals of the region, a multilocus DNA sequence typing (MLST) approach was applied. Water distribution systems in four departments belonging to four Sardinian hospitals were sampled. Fusarium species and sequence types (STs) were identified using MLST based on sequences of the elongation factor 1-alpha (EF-1α) gene, the nuclear ribosomal DNA intergenic spacer region (IGS rDNA), and/or a portion of the second-largest subunit of RNA polymerase (RPB2) gene. The majority of isolates obtained from Sardinian hospitals (90.7%) were identified as representatives of the Fusarium oxysporum species complex (FOSC), followed by those of the F. solani species complex (FSSC) (8.2%), and F. dimerum (1.1% of all isolates). Ten STs were found among the FOSC and FSSC, with more than 60% of the isolates identified as either FOSC ST 33 or FSSC 1 (F. petroliphilum). More than half of the FOSC isolates obtained from the water systems in all four hospitals belonged to the worldwide distributed clonal lineage ST 33. This haplotype is the most prevalent among the FOSC in different countries, being responsible for the vast majority of cases of human fusariosis.

Biocontrol Activity of Bacillus megaterium BM344-1 against Toxigenic Fungi

Mycotoxins are secondary metabolites of some fungal species and represent important contaminants of food and feed. This study aimed to explore the biological control activity of Bacillus megaterium BM344-1 volatile organic compounds (VOCs) on the growth and mycotoxin production of single representatives of the toxigenic species Aspergillus flavus, Aspergillus carbonarius, Penicillium verrucosum, and Fusarium verticillioides. In vitro co-incubation experiments indicated the P. verrucosum isolate as the most sensitive one, with a growth inhibition ratio of 66.7%, followed by A. flavus (29.4%) and F. verticillioides (18.2%). Exposure of A. flavus, P. verrucosum, and F. verticillioides to BM344-1 VOCs resulted in complete inhibition of aflatoxins (AFB₁, AFG₁, and AFG₂), ochratoxin A, and fumonisin B₁ (FB₁) synthesis on artificial media, respectively. In vivo experiments on maize kernels showed 51% inhibition of fungal growth on ears simultaneously infected with A. flavus spores and exposed to BM344-1 volatiles. Likewise, AF synthesis by A. flavus was significantly (p < 0.05) inhibited (25.34 ± 6.72 μg/kg) by bacterial volatiles as compared to that in control maize ears (91.81 ± 29.10 μg/kg). Gas chromatography-tandem mass spectrometry-based analysis of headspace volatiles revealed hexadecanoic acid methyl ester (palmitic acid) and tetracosane as bioactive compounds in the BM344-1 volatilome. Bacterial volatiles have promising potential to control the growth and mycotoxin synthesis of toxigenic fungi and may present valuable aid in the efforts to warrant food and feed safety.

Prenylated Trans-Cinnamic Esters and Ethers against Clinical Fusarium spp.: Repositioning of Natural Compounds in Antimicrobial Discovery

Onychomycosis is a common nail infection mainly caused by species belonging to the F. oxysporum, F. solani, and F. fujikuroi species complexes. The aim of this study was to evaluate the in vitro susceptibility of six representative strains of clinically relevant Fusarium spp. toward a set of natural-occurring hydroxycinnamic acids and their derivatives with the purpose to develop naturally occurring products in order to cope with emerging resistance phenomena. By introducing a prenylated chain at one of the hydroxy groups of trans-cinnamic acids 1–3, ten prenylated derivatives (coded 4–13) were preliminarily investigated in solid Fusarium minimal medium (FMM). Minimal inhibitory concentration (MIC) and lethal dose 50 (LD₅₀) values were then determined in liquid FMM for the most active selected antifungal p-coumaric acid 3,3′-dimethyl allyl ester 13, in comparison with the conventional fungicides terbinafine (TRB) and amphotericin B (AmB), through the quantification of the fungal growth. Significant growth inhibition was observed for prenylated derivatives 4–13, evidencing ester 13 as the most active. This compound presented MIC and LD₅₀ values (62–250 µM and 7.8–125 µM, respectively) comparable to those determined for TRB and AmB in the majority of the tested pathogenic strains. The position and size of the prenylated chain and the presence of a free phenol OH group appear crucial for the antifungal activity. This work represents the first report on the activity of prenylated cinnamic esters and ethers against clinical Fusarium spp. and opens new avenues in the development of alternative antifungal compounds based on a drug repositioning strategy.

Naturally Occurring Phenols Modulate Vegetative Growth and Deoxynivalenol Biosynthesis in Fusarium graminearum

To assess the in vitro activity of five naturally occurring phenolic compounds (ferulic acid, apocynin, magnolol, honokiol, and thymol) on mycelial growth and type B trichothecene mycotoxin accumulation by Fusarium graminearum, three complementary approaches were adopted. First, a high-throughput photometric continuous reading array allowed a parallel quantification of F. graminearum hyphal growth and reporter TRI5 gene expression directly on solid medium. Second, RT-qPCR confirmed the regulation of TRI5 expression by the tested compounds. Third, liquid chromatography-tandem mass spectrometry analysis allowed quantification of deoxynivalenol (DON) and its acetylated forms released upon treatment with the phenolic compounds. Altogether, the results confirmed the activity of thymol and an equimolar mixture of thymol-magnolol at 0.5 mM, respectively, in inhibiting DON production without affecting vegetative growth. The medium pH buffering capacity after 72-96 h of incubation is proposed as a further element to highlight compounds displaying trichothecene inhibitory capacity with no significant fungicidal effect.

Isolation of a Novel Kluyveromyces marxianus Strain QKM-4 and Evidence of Its Volatilome Production and Binding Potentialities in the Biocontrol of Toxigenic Fungi and Their Mycotoxins

To overcome the economic losses associated with fungi and their toxic metabolites, environmentally safe and efficient approaches are needed. To this end, biological control using yeasts and safe bacterial strains and their products are being explored to replace synthetic fungicides. In the present study, the biocontrol effect of a yeast strain of Kluyveromyces marxianus, QKM-4, against the growth and mycotoxin synthesis potential of key toxigenic fungi was evaluated. In vitro assays were performed to find the application of yeast volatile organic compounds (VOCs) against fungal contamination on important agricultural commodities. The removal of ochratoxin A (OTA) and deoxynivalenol (DON) by living and heat-inactivated yeast cells was also explored. VOCs produced by strain QKM-4 were able to significantly limit the fungal growth of 17 fungal species belonging to genera Aspergillus, Penicillium, and Fusarium. Yeast VOCs were able to reduce OTA biosynthesis potential of Penicillium verrucosum and Aspergillus carbonarius by 99.6 and 98.7%, respectively. In vivo application of QKM-4 VOCs against Fusarium oxysporum and A. carbonarius infection on tomatoes and grapes, respectively, determined a complete inhibition of fungal spore germination. GC/MS-based analysis of yeast VOCs identified long-chain alkanes, including nonadecane, eicosane, docosane, heptacosane, hexatriacontane, and tetracosane. In vitro testing of the mycotoxin-binding potential of the living and heat-inactivated QKM-4 cells showed a reduction of OTA and DON up to 58 and 49%, respectively, from artificially contaminated buffers. Our findings clearly demonstrate the strong antifungal potential of K. marxianus QKM-4 and propose this strain as a strong candidate for application in agriculture to safeguard food and feed products.

Scent of a Killer: Microbial Volatilome and Its Role in the Biological Control of Plant Pathogens

The use of synthetic fungicides represents the most common strategy to control plant pathogens. Excessive and/or long-term distribution of chemicals is responsible for increased levels of environmental pollution, as well as adverse health consequence to humans and animals. These issues are deeply influencing public perception, as reflected by the increasing demand for safer and eco-friendly agricultural commodities and their by-products. A steadily increasing number of research efforts is now devoted to explore the use of safer and innovative approaches to control plant pathogens. The use of microorganisms as biological control agents (BCAs) represents one of the most durable and promising strategies. Among the panoply of microbial mechanisms exerted by BCAs, the production of volatile organic compounds (VOCs) represents an intriguing issue, mostly exploitable in circumstances where a direct contact between the pathogen and its antagonist is not practicable. VOCs are potentially produced by all living microorganisms, and may be active in the biocontrol of phytopathogenic oomycetes, fungi, and bacteria by means of antimicrobial activity and/or other cross-talk interactions. Their biological effects, the reduced residuals in the environment and on agricultural commodities, and the ease of application in different agricultural systems make the use of VOCs a promising and sustainable approach to replace synthetic fungicides in the control of plant pathogens. In this review, we focus on VOCs produced by bacteria and fungi and on their role in the cross-talk existing between the plant pathogens and their host. Biologic systemic effect of the microbial volatile blends on both pathogen and host plant cells is also briefly reviewed.

Investigation and Application of Bacillus licheniformis Volatile Compounds for the Biological Control of Toxigenic Aspergillus and Penicillium spp

The present study was designed to investigate the antagonistic activity of Bacillus licheniformis BL350-2 against mycotoxigenic strains of Aspergillus and Penicillium. In vitro coincubation for 5 days indicated Aspergillus westerdijkiae BA1 as the most sensitive strain, with a growth inhibition of 62%, followed by A. carbonarius MG7 (60%), Penicillium verrucosum MC12 (53%), A. niger MC05 (50%), A. flavus CM5 (49%), A. parasiticus SB01 (47%), and A. ochraceus MD1 (44%). Likewise, the majority of the tested strains on exposure to bacterial volatiles showed complete inhibition of mycotoxin synthesis. In vivo assays on maize ears resulted in 88% reduction in A. flavus CM5 growth and complete inhibition of fungal sporulation and aflatoxin accumulation. The GC-MS-based volatile profile showed 3-methyl-1-butanol as the most abundant compound. The findings of the present study advocate that B. licheniformis BL350-2 is suitable as a biocontrol agent against mycotoxigenic fungi, at least during storage of cereal grains.

Biocontrol yeasts: mechanisms and applications

Yeasts occur in all environments and have been described as potent antagonists of various plant pathogens. Due to their antagonistic ability, undemanding cultivation requirements, and limited biosafety concerns, many of these unicellular fungi have been considered for biocontrol applications. Here, we review the fundamental research on the mechanisms (e.g., competition, enzyme secretion, toxin production, volatiles, mycoparasitism, induction of resistance) by which biocontrol yeasts exert their activity as plant protection agents. In a second part, we focus on five yeast species (Candida oleophila, Aureobasidium pullulans, Metschnikowia fructicola, Cryptococcus albidus, Saccharomyces cerevisiae) that are or have been registered for the application as biocontrol products. These examples demonstrate the potential of yeasts for commercial biocontrol usage, but this review also highlights the scarcity of fundamental studies on yeast biocontrol mechanisms and of registered yeast-based biocontrol products. Yeast biocontrol mechanisms thus represent a largely unexplored field of research and plentiful opportunities for the development of commercial, yeast-based applications for plant protection exist.

Honokiol, magnolol and its monoacetyl derivative show strong anti-fungal effect on Fusarium isolates of clinical relevance

The antifungal activity of magnolol and honokiol, two naturally occurring hydroxylated biphenyls, and of their synthetic derivatives was evaluated on a collection of representative isolates of Fusarium oxysporum, F. solani and F. verticillioides of clinical and ecological concern. The tested compounds were proposed as a ‘natural’ alternative to conventional fungicides, even though a larger range of concentrations (5–400 μg/ml) was applied. The activity of magnolol and honokiol was compared with that of terbinafine (0.1–10 μg/ml), and fluconazole (1–50 μg/ml), two fungicides widely used in treating fungal infections on humans. Magnolol showed similar fungicidal activity compared to fluconazole, whereas honokiol was more effective in inhibiting mycelium growth compared to this fungicide on all tested clinical Fusarium spp. isolates. Compared to terbinafine, honokiol showed similar antifungal activity when tested on clinical F. solani isolates, whereas magnolol was less effective at all selected concentrations (5–400 μg/ml). The different position of the phenol-OH group, as well as its protection, explain different in vitro activities between magnolol, honokiol, and their derivatives. Furthermore, magnolol showed mycelium dry weight reduction at a concentration of 0.5 mM when tested on a set of agricultural isolates of Fusaria, leading to complete inhibition of some of them. Magnolol and honokiol are proposed as efficient and safe candidates for treating clinically relevant Fusaria.