Field evaluation of an entomopathogenic fungus, Metarhizium brunneum strain F52, against pear psylla, Cacopsylla pyri

Pathogenicity against hemipteran vector insects of a novel insect pathogenic fungus from Entomophthorales (Pandora sp. nov. inedit.) with potential for biological control

A new but still unpublished entomopathogenic fungus (ARSEF13372) in the genus Pandora (Entomophthorales: Entomophthoraceae) was originally isolated from Cacopsylla sp. (Hemiptera: Psyllidae). Several species of the genus Cacopsylla vector phloem-borne bacteria of the genus 'Candidatus Phytoplasma', which cause diseases in fruit crops such as apple proliferation, pear decline and European stone fruit yellows. To determine Pandora's host range and biocontrol potential we conducted laboratory infection bioassays; Hemipteran phloem-feeding insects were exposed to conidia actively discharged from in vitro produced mycelial mats of standardized area. We documented the pathogenicity of Pandora sp. nov. to species of the insect families Psyllidae and Triozidae, namely Cacopsyllapyri L., C.pyricola (Foerster), C.picta (Foerster, 1848), C.pruni (Scopoli), C.peregrina (Foerster), and Trioza apicalis Foerster. The occurrence of postmortem signs of infection on cadavers within 10 days post inoculation proved that Pandora sp. nov. was infective to the tested insect species under laboratory conditions and significantly reduced mean survival time for C.pyri (summer form and nymph), C.pyricola, C.picta, C.pruni, C.peregrina and T.apicalis. Assessing a potential interaction between phytoplasma, fungus and insect host revealed that phytoplasma infection ('Candidatus Phytoplasma mali') of the vector C.picta and/or its host plant apple Malus domestica Borkh. did not significantly impact the survival of C.picta after Pandora sp. nov. infection. The results from infection bioassays were discussed in relation to Pandora sp. nov. host range and its suitability as biocontrol agent in integrated pest management strategies of psyllid pests, including vector species, in orchards.

Peppermint Essential Oil Toxicity to the Pear Psylla (Hemiptera: Psyllidae) and Potential Applications in the Field

Chinese pear psylla (Cacopsylla chinensis Yang et Li) is a serious orchard pest that causes declines in fruit quality through feeding damage and the spread of pathogens. The rapid development of chemical pesticide resistance has become a severe problem in controlling pear psylla. Thus, the development of natural pesticides to replace conventional chemical pesticides is urgently needed. Here, we found that the essential oil of peppermint (Mentha haplocalyx Briq. [Lamiales: Labiatae]) is an ideal agent for controlling pear psylla based on experiments in the laboratory and the field. The major constituents of peppermint essential oil were found including menthol (49.73%), menthone (30.52%), α-pinene (3.60%), and α-terpineol (3.81%). This oil and chemicals in it performed serious contact toxicity against the winter-form adults and nymphs of pear psylla, yielding LD50 values of 2.54, 10.71, 2.77, 5.85, and 12.58 μg/adult and 1.91, 9.56, 2.18, 4.98, and 12.07 μg/nymph, respectively. Furthermore, the essential oil strongly repelled the adults of pear psylla with 78% repellence at the highest concentration tested in a Y-tube olfactometer in the laboratory. The combined effect of the two factors made peppermint essential oil a natural pesticide, which achieved a maximum reduction of round to 80.9% in winter-form adult population and round to 67.0% in nymph population at the concentration of 4.0 ml/L in the field. Additionally, it had no effect on the natural enemies of pear psylla in the field. Therefore, peppermint essential oil has potential as an alternative to chemical pesticides for pest control in integrated pest management programs in pear orchards.

Performance of Three Isolates of Metarhizium Anisopliae and Their Virulence against Zeugodacus Cucurbitae under Different Temperature Regimes, with Global Extrapolation of Their Efficiency

The performance of entomopathogenic fungi in pest control is usually affected by both biotic and abiotic factors. This study aimed to determine the effects of various temperatures (15, 20, 25 and 30 °C) on conidial germination, mycelial growth and conidial density and virulence to the melon fly Zeugodacus cucurbitae of three selected isolates of Metarhizium anisopliae. The three isolates, ICIPE 18, ICIPE 30 and ICIPE 69, had previously been selected in laboratory bioassays. Percentage mortality by the three isolates ranged between 16.25% and 100.0% across the different temperatures. The isolates ICIPE 69 and ICIPE 18 recorded the highest percentage mortality of 96.25% and 100% and the shortest LT₅₀ values of 2.61 and 2.63 days, respectively, at 30 °C. However, at 30 °C, ICIPE 69 produced the highest number of conidia of 90.5 × 10⁷ /mL and was therefore selected for global mapping to predict its efficacy against Z. cucurbitae using the geospatial temperature data layer and the best fitted quadratic model. The map showed that the isolate would be more effective in the tropics than in temperate climates.

Laboratory Screening of 26 Essential Oils Against Cacopsylla chinensis (Hemiptera: Psyllidae) and Field Confirmation of the Top Performer, Perilla frutescens (Lamiales: Lamiaceae)

Similar to other pear psylla species in Europe and America, Cacopsylla chinensis (Yang and Li) is one of the most important pests that causes yield loss in commercial pear orchards in China. To investigate effective essential oils as alternatives to conventional pesticides against C. chinensis, 26 essential oils derived from commonly used Chinese spices and medicinal herbs were screened for insecticidal activity. Among these, the essential oil from Perilla frutescens (L.) Britton leaves was the top performer; it exhibited strong and acute toxicity against pear psylla, with an LD50 value of 0.63 μg per adult. Then, we tested the constituents of the essential oil and its toxicity in the field. Field trials showed a 72% corrected reduction in the first-second-instar population 7 d after spraying P. frutescens leaf oil solution at a concentration of 1 mg/ml and a 47% corrected reduction at days 3 and 14. This report is the first to document the application of essential oil from P. frutescens leaves to control C. chinensis under field conditions. Our results suggest that P. frutescens oil can be considered a novel potential pesticide for C. chinensis control in pear orchards.

Insecticidal Potential of Clove Essential Oil and Its Constituents on Cacopsylla chinensis (Hemiptera: Psyllidae) in Laboratory and Field

Cacopsylla chinensis (Yang and Li) (Hemiptera: Psyllidae) is an important pest of pear in China. As an alternative to conventional chemical pesticides, botanicals including essential oils and their constituents could provide an eco-friendly and nonhazardous control method. In this study, the essential oil of clove buds (Syzygium aromaticum) was obtained by hydrodistillation. Five constituents, accounting for 99.89% of the oil, were identified by gas chromatography-mass spectrometry, and the major constituents were eugenol (88.61%) and eugenol acetate (8.89%), followed by β-caryophyllene (1.89%). In a laboratory bioassay, clove essential oil, commercial eugenol (99.00%) and β-caryophyllene (98.00%) exhibited strong contact toxicity against the summerform adults of C. chinensis with LD50 values of 0.730, 0.673, and 0.708 µg/adult, and against the nymphs with LD50 values of 1.795, 1.668, and 1.770 µg/nymph, respectively. In contrast, commercial eugenol acetate (98%) had LD50 values of 9.266 µg/adult and 9.942 µg/nymph. In a field trial, clove essential oil caused significant population reductions of 73.01% (4.80 mg/ml), 66.18% (2.40 mg/ml) and 46.56% (1.20 mg/ml), respectively. Our results demonstrated that clove essential oil and its constituents have potential as a source of natural insecticides.