Current Strategies and Future Outlook for Managing the Neotropical Tomato Pest Tuta absoluta (Meyrick) in the Mediterranean Basin

Heteropteran Bugs Assemblage Associated to Organic Tomato Farms: Knowledge for Pest Management

The suborder Heteroptera (Hemiptera) includes zoophagous and zoophytophagous species which conform diverse natural enemies' systems with potential to control several horticultural pests. In this study, we report the assemblage structure of heteropteran bugs species inhabiting open-field and greenhouse organic tomato crops and one common adjacent non-crop solanaceous plant, Solanum sisymbriifolium, in North Buenos Aires province, Argentina, aimed to select promissory biocontrol species. Biweekly direct inspection of selected plants was carried out during a 3-year period (2017-2019) to collect hemipteran nymphs and adults. As a result, nine species and morphospecies belonging to Berytidae (zoophytophagous), Lygaeidae (phytophagous), and Miridae (phytophagous and zoophytophagous) were found, with ≥ 75% of species belonging to the latter family. The zoophytophagous mirid Tupiocoris cucurbitaceus (Spinola) was the most frequent and dominant species in all sites studied. Among the phytophagous species, Nysius simulans Stål was mostly present in greenhouse crops. The community found in greenhouse tomato crops was more diverse than that registered in open-field crops. The characterization of the heteropteran complex in organic tomato farms provides basic knowledge necessary to design pest control strategies in the region studied.

Few indirect effects of baculovirus on parasitoids demonstrate high compatibility of biocontrol methods against Tuta absoluta

BACKGROUND

Combining different biocontrol agents, particularly micro- and macroorganisms, can contribute to new and sustainable pest control approaches. Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of solanaceous crops. An emerging management strategy consists of biological control using microbial insecticides such as baculoviruses, but with limited efficacy. Thanks to their high target specificity, baculoviruses can be used simultaneously with natural enemies such as parasitoids for improved control of T. absoluta. However, potential indirect nontarget effects of baculoviruses on parasitoids can result from overlapping resource requirements. We assessed whether ovipositing parasitoid females discriminated against virus-treated hosts and examined the outcome of within-host competition between the hymenopteran parasitoids Necremnus tutae (Reuter) (Eulophidae) and Dolichogenidea gelechiidivoris Marsch (Braconidae), and the Phthorimaea operculella granulovirus (PhopGV, Baculoviridae) that infects T. absoluta larvae.

RESULTS

Female D. gelechiidivoris discriminated against virus-treated hosts, whereas N. tutae did not. We found few indirect virus-related effects depending on the species, the sex, and the time of virus treatment. Effects were ambivalent for D. gelechiidivoris offspring and ranged from increased male longevity when infection occurred before parasitization to reduced emergence and male longevity when infection occurred after parasitization. N. tutae offspring showed a longer development time and shorter male longevity when they developed in virus-treated hosts.

CONCLUSION

The virus had a low impact on parasitoid offspring. In rare cases, adverse effects were detected; however, the low magnitude of these effects is unlikely to reduce the fitness of parasitoid offspring, therefore both parasitoids seem compatible with the baculovirus for control of T. absoluta. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Non-host plant odors influence the tritrophic interaction between tomato, its foliar herbivore Tuta absoluta and mirid predator Nesidiocoris tenuis

The tomato leafminer, Tuta absoluta is a destructive invasive pest of cultivated tomato and other Solanaceae plants, with yield losses of 80-100%. Mirid predators are key natural enemies of T. absoluta, but they also feed on host plants in the absence of their prey. Management of T. absoluta is a challenge due to its high biotic potential, resistance to many insecticides and the absence of sufficiently adapted auxiliary fauna in its new dispersion zones. Olfaction plays an important role in the tritrophic interaction between tomato, its herbivore pest T. absoluta and its mirid predators, which can be influenced by non-host plant odors. However, how non-host odours shape this interaction is poorly understood. Previously, we had demonstrated belowground crop protection properties of certain Asteraceae plants against the root-knot nematode Meloidogyne incognita, pest of tomato and other Solanaceae plants. Additionally, Asteraceae plants impact negatively on feeding behavior of above-ground pests of Solanaceae plants, including the greenhouse whitefly (Trialeurodes vaporariorum) and green peach aphid (Myzus persicae). Here, we tested the hypothesis that foliar volatiles from some of these non-host Asteraceae plants can influence the tomato-T. absoluta-mirid predator tritrophic interaction. In olfactometer assays, T. absoluta females were attracted to volatiles of the Solanaceae host plants tomato and giant nightshade but avoided volatiles of the Asteraceae plants, blackjack and marigold, and the positive control, wild tomato, when tested alone or in combination with the host plants. Coupled gas chromatography-mass spectrometry analysis showed that host and non-host plants varied in their emission of volatiles, mainly monoterpenes and sesquiterpenes. Random forest analysis combined with behavioral assays identified monoterpenes as the host plant attractive blend to T. absoluta and its mirid predator, with sesquiterpenes identified as the non-host plant repellent blend against T. absoluta. Contrastingly, the mirid predator was indifferent to the non-host plant repellent sesquiterpenes. Our findings indicate that terpenes influence the tomato-T. absoluta-mirid predator tritrophic interaction. Further, our results emphasize the importance of studying crop protection from a holistic approach to identify companion crops that serve multi-functional roles.

Genomic and metabolic profiling of two tomato contrasting cultivars for tolerance to Tuta absoluta

Dissimilar patterns of variants affecting genes involved in response to herbivory, including those leading to difference in VOC production, were identified in tomato lines with contrasting response to Tuta absoluta. Tuta absoluta is one of the most destructive insect pest affecting tomato production, causing important yield losses both in open field and greenhouse. The selection of tolerant varieties to T. absoluta is one of the sustainable approaches to control this invasive leafminer. In this study, the genomic diversity of two tomato varieties, one tolerant and the other susceptible to T. absoluta infestation was explored, allowing us to identify chromosome regions with highly dissimilar pattern. Genes affected by potential functional variants were involved in several processes, including response to herbivory and secondary metabolism. A metabolic analysis for volatile organic compounds (VOCs) was also performed, highlighting a difference in several classes of chemicals in the two genotypes. Taken together, these findings can aid tomato breeding programs aiming to develop tolerant plants to T. absoluta.

Review: Presence, distribution and current pesticides used in Spanish agricultural practices

To guarantee an adequate food supply for the world's growing population, intensive agriculture is necessary to ensure efficient food production. The use of pesticides helps maintain maximum productivity in intensive agriculture by minimizing crop losses due to pests. However, pesticide contamination of surface waters constitutes a major problem as they are resistant to degradation and soluble enough to be transported in water. In recent years, all groups of pesticides defined by the World Health Organization have increased their use and, therefore, their prevalence in the different environmental compartments that can have harmful effects. Despite this effort, there is no rigorous monitoring program that quantifies and controls the toxic effects of each pesticide. However, multiple scientific studies have been published by specialized research groups in which this information is disseminated. Therefore, any attempt to systematize this information is relevant. This review offers a current overview of the presence and distribution of the most widely-used pesticides (insecticides, herbicides, and fungicides) by crop type and an evaluation of the relationships between their uses and environmental implications in Spain. The data demonstrated that there are correlations between the presence of specific pesticides used in the main crops and their presence in the environmental compartments. We have found preliminary data pointing to existing associations between specific pesticides used in the main crops and their presence in environmental compartments within different geographical areas of Spain; this should be the subject of further investigation.

A Fuzzy-Based Model to Predict the Spatio-Temporal Performance of the Dolichogenidea gelechiidivoris Natural Enemy against Tuta absoluta under Climate Change

The South American tomato pinworm, Tuta absoluta, causes up to 100% tomato crop losses. As Tuta absoluta is non-native to African agroecologies and lacks efficient resident natural enemies, the microgastrine koinobiont solitary oligophagous larval endoparasitoid, Dolichogenidea gelechiidivoris (Marsh) (Syn.: Apanteles gelechiidivoris Marsh) (Hymenoptera: Braconidae) was released for classical biological control. This study elucidates the current and future spatio-temporal performance of D. gelechiidivoris against T. absoluta in tomato cropping systems using a fuzzy logic modelling approach. Specifically, the study considers the presence of the host and the host crop, as well as the parasitoid reproductive capacity, as key variables. Results show that the fuzzy algorithm predicted the performance of the parasitoid (in terms of net reproductive rate (R0)), with a low root mean square error (RMSE) value (<0.90) and a considerably high R2 coefficient (=0.98), accurately predicting the parasitoid performance over time and space. Under the current climatic scenario, the parasitoid is predicted to perform well in all regions throughout the year, except for the coastal region. Under the future climatic scenario, the performance of the parasitoid is projected to improve in all regions throughout the year. Overall, the model sheds light on the varying performance of the parasitoid across different regions of Kenya, and in different seasons, under both current and future climatic scenarios.

Comparing, evaluating and combining statistical species distribution models and CLIMEX to forecast the distributions of emerging crop pests

BACKGROUND

Forecasting the spread of emerging pests is widely requested by pest management agencies in order to prioritise and target efforts. Two widely used approaches are statistical Species Distribution Models (SDMs) and CLIMEX, which uses ecophysiological parameters. Each have strengths and weaknesses. SDMs can incorporate almost any environmental condition and their accuracy can be formally evaluated to inform managers. However, accuracy is affected by data availability and can be limited for emerging pests, and SDMs usually predict year-round distributions, not seasonal outbreaks. CLIMEX can formally incorporate expert ecophysiological knowledge and predicts seasonal outbreaks. However, the methods for formal evaluation are limited and rarely applied. We argue that both approaches can be informative and complementary, but we need tools to integrate and evaluate their accuracy. Here we develop such an approach, and test it by forecasting the potential global range of the tomato pest Tuta absoluta.

RESULTS

The accuracy of previously developed CLIMEX and new statistical SDMs were comparable on average, but the best statistical SDM techniques and environmental data substantially outperformed CLIMEX. The ensembled approach changes expectations of T. absoluta's spread. The pest's environmental tolerances and potential range in Africa, the Arabian Peninsula, Central Asia and Australia will be larger than previous estimates.

CONCLUSION

We recommend that CLIMEX be considered one of a suite of SDM techniques and thus evaluated formally. CLIMEX and statistical SDMs should be compared and ensembled if possible. We provide code that can be used to do so when employing the biomod suite of SDM techniques. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluation of the effectiveness of Neoseiulus cucumeris (Oudemans) as a predator of Tuta absoluta (Meyrick)

The leaf miner, Tuta absoluta is continue to be a serious threat to solanaceous plants, especially tomato plant worldwide. Tomato crop in Saudi Arabia has been recently affected by T. absoluta, which is difficult to control due to its unique biological features, such as high fecundity and its potential to develop resistance to chemical pesticides. In this article, the suitability and effectiveness of the predatory mite, Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), an indigenous species usually found in tomato greenhouses of northcentral Saudi Arabia, has been evaluated on eggs and 1st instar larvae of T. absoluta in the laboratory. All experiments were conducted in an incubator at three constant temperatures of 22, 27 and 32°C ± 1°C, 50 ± 4% R.H. and L12:D12 h photoperiod. Adult females and males of N. cucumeris were able to feed and sustain oviposition on eggs and 1st instar larvae of T. absoluta, and could be an effective biocontrol agent against T. absoluta. The N. cucumeris had a clear preference for eggs compared to 1st instar larvae of T. absoluta. The results showed the obvious effect of the temperature on the consumption rate of the predatory mite. The maximum daily consumption rate occurred during the oviposition period, when the females of the predatory mite consumed an average of 4.26 eggs and 2.44 1st instar larvae of T. absoluta. In general, total fecundity was high with T. absoluta eggs as a food source when temperature increased from 22 to 32°C. The highest fecundity rate (42.92 and 20.97 eggs /female) was recorded at 32°C, while the lowest one (26.77 and 10.12 eggs / female) was recorded at 22°C, when N. cucumeris female fed on eggs and 1st instar larvae of T. absoluta, respectively. The results of this study indicated that the predatory mite, N. cucumeris can be considered a promising potential candidate for controlling the leaf miner T. absoluta, and further research is required to assess its effectiveness under greenhouse conditions.

Effectiveness of bio-insecticides and mass trapping based on population fluctuations for controlling Tuta absoluta under greenhouse conditions in Albania

Tuta absoluta is a major pest of tomato crops that causes high yield losses. Cultivated areas in Albania have reported high levels of infestations despite the application of control measures. The present study aims to describe population fluctuations of T. absoluta during tomato cultivation for three consecutive years in the winter–summer growing season under greenhouse conditions. Delta traps baited with pheromones were used to monitor the population fluctuations, and the appropriate treatment period was determined. The effectiveness of mass trapping, Indoxacarb and Bacillus thuringiensis treatments at maintaining the pest populations below the economic injury level was tested. Even under greenhouse conditions, the population levels were high during spring and peaked in summer. The infestation rate increased by up to 85% on leaves and fruit. The application of Bt, Indoxacarb, and mass trapping reduced the infestation rate on fruits by approximately 29%, 43% and 52%, respectively, which represented significant differences in effectiveness. In conclusion, the results indicate that performing an intervention that includes combined methods in the proper period might reduce the infestation rate from 80-95%.

Influence of insect traps and insecticides sequential application as a tactic for management of tomato leafminer, Tuta absoluta (Meyrick), (Lepidoptera: Gelechiidae)

Background

Tomato crop, Lycopersicon esculentum L. (Solanaceae), usually attacked by many insect species, including the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), where its larvae cause damage up to 80–100% by due to its feeding habits by making tunnels in all tomato parts. The influence of insect traps application and insecticides sequential as a tactic for T. absoluta management was carried out.

Results

Sex pheromone and sticky traps were used for mass trapping this pest; sex pheromone traps were more effective than the sticky one; the number of caught insects was higher in the untreated plots than the treated one. Also, the general mean number of captured insects by sex pheromone traps was 432.89 and 633.40 (vegetative stage) and 691.3 and 1865.5 (fruiting stage) adults/trap/week, for treatment and control, respectively. When the first infestation appeared, the non-conventional insecticides were consecutively sprayed once/week for 3 weeks with the following order: Radiant, Coragen, and Emperor (during the vegetative stage). After that, the formulated essential oils Nimbecidine (commercial) and Rosa (prepared) were respectively sprayed twice/week for 2 weeks (during the fruiting stage). The general average of reduction in infestation reached 95.81% when non-conventional insecticides were used, while it reached 92.15% when the formulated essential oils were used. Finally, at the end of the experiment, promising mean reduction in infestation reached 93.98% was achieved. Yield of marketable healthy fruits was recorded and expressed as ton/feddan. Treatments gave significantly higher yield over untreated control. The tomato yield reached 28.25 t/fed. compared with control (8.35 t/fed.), which gain 19.94 t/fed. equal to 238.32% more than the untreated control.

Conclusions

The results indicated that insect traps and insecticides sequential application as a tactic for management T. absoluta were more effective; the rotation of insecticides avoid build up resistance and achieved satisfied reduction (93.98%) in the infestation and high yield production.

Effect of Temperature on Life History and Parasitization Behavior of Trichogramma achaeae Nagaraja and Nagarkatti (Hym.: Trichogrammatidae)

Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) is currently used as biological control agent for several lepidopteran pests. Knowledge of thermal requirements is essential to optimize its rearing procedures and inundative releases. The biological characteristics and two-sex life table parameters of T. achaeae were determined at five constant temperatures (15, 20, 25, 30, and 35 °C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. T. achaeae was able to develop and survive from 15 °C to 30 °C, but not at 35 °C. Temperature significantly affected the preadult development time and adult longevity, decreasing when temperature increased from 15 °C to 30 °C. Temperature significantly altered the sex ratio, being female biased between 15 °C and 25 °C. Age-stage, two-sex life table analysis indicated that net reproductive rate (R₀) was highest at 20 °C. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased with increasing temperature, while the mean generation time (T) decreased significantly. In addition, functional response of T. achaeae was studied, being significantly affected by temperature and host egg density, displaying a Holling type-I at 15 °C and a Holling type-II at 25 °C. The relevance of these results is discussed for the use of T. achaeae as biological control agent.

First Report Using a Native Lacewing Species to Control Tuta absoluta: From Laboratory Trials to Field Assessment

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), a destructive pest on tomato, has invaded most Afro-Eurasian countries. Recently invaded by the pest, most tomato crops in greenhouses and open fields in Tajikistan are currently suffering major damage. While failure in management using chemical insecticide has been frequently observed, alternative options such as biological control is urgently needed. In this study, we evaluated the effectiveness of the common green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) against T. absoluta. In controlled laboratory conditions, C. carnea showed high predation rate on both T. absoluta eggs (i.e., 36 ± 2 eggs within 24 h and 72 ± 4 eggs within 48 h) and larvae, especially it can attack the larvae both inside and outside the leaf galleries (i.e., an average of 22% of the larvae was killed inside, and an average of 35% was killed outside). In a cage exclusion experiment, T. absoluta showed relatively low larval density in the cages with pre-fruiting release of C. carnea, whereas the larval density was four to six times higher in the “no release” cages. In the “post-fruiting release” cages, the pest population that had already built up during the pre-fruiting stage eventually crashed. In an open-field experiment, the tomato crops in control plots were fully destroyed, whereas low levels of larvae density and damage were observed in the biocontrol plots. Moreover, the field release of C. carnea resulted in significantly higher tomato yield than those without release, despite no differences between the “pre-fruiting release” and “post-fruiting release” treatments. We conclude that the local commercial biocontrol agent C. carnea could be promising for the management of T. absoluta in Tajikistan. It is also one of the first reports showing the management of T. absoluta using a lacewing species. The effectiveness should be validated by further field trials in larger area of commercial crops and various locations.

Influence of Age, Host Plant and Mating Status in Pheromone Production and New Insights on Perception Plasticity in Tuta Absoluta

The tomato leafminer Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is one of the most important pests of tomato worldwide. However, in spite of its tremendous economic importance, the success of environmentally friendly measures to control the pest is still limited. Study of physiological and behavioral parameters that affect pheromone production has provided useful information for pest management. Our results show no clear difference in pheromone production by females over the period from 2 h before to 2 h after the scotophase. However, pheromone production was clearly dependent on female age, with young females producing the highest amount of each pheromone component 10 days after emergence. In the presence of the host plant (physical contact and olfaction of the plant volatiles), virgin and mated females produced higher amounts of the major component of the pheromone (TDTA) than those in the absence of plant and those devoid of olfaction (antennectomized) but in physical contact with the plant. In electrophysiological experiments, TDTA elicited slightly lower responses on male antennae than the pheromone mixture. When stimulated at certain time intervals after the first exposure to TDTA, male antennae became more sensitive to the stimulus (sensitization effect). For the first time in an insect of the family Gelechiidae, we have found that females are able to detect their own pheromone (autodetection). Altogether, our results may represent a step forward in the knowledge of the chemical communication of this important pest.