Laboratory evaluation of the compatibility of Beauveria bassiana with the egg parasitoid Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) for joint application against the oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae)

Abstract

BACKGROUND The entomopathogenic fungus Beauveria bassiana and the egg parasitoid Trichogramma dendrolimi can both contribute to biological control of the global fruit borer Grapholita molesta. To derive insights for optimizing their combined application in augmentation programs, we assayed fungal pathogenicity to both G. molesta (eggs, larvae and adults) and adult parasitoids, and assessed wasp acquisition and transmission of fungal spores following their emergence from B. bassiana‐treated host eggs. RESULTS Concentrations of 108 conidia mL−1 of B. bassiana and higher caused virtually complete mortality of G. molesta larvae, but less than 30% mortality of eggs, and female moths surviving treatments had reduced fecundity. More than 80% of adult T. dendrolimi survived B. bassiana treatments of 107 conidia mL−1, and more than 60% survived 109 conidia mL−1, with surviving females achieving reproductive success equivalent to controls. Parasitoid females preferred healthy eggs over B. bassiana‐infected ones in choice tests; wasps emerging from treated eggs carried about 104 conidia each and contributed an additional 11% host mortality in trials combining both agents. CONCLUSION Our results indicate that combined applications of B. bassiana and T. dendrolimi can have complimentary impacts on G. molesta, the wasps compensating for low fungal pathogenicity to eggs and their progeny potentially aiding in subsequent disease transmission. Although foraging wasps tended to avoid infected eggs, negative interactions between the two agents might be further mitigated by timing B. bassiana applications from late instar larva to early moth stage, and T. dendrolimi releases several days later to coincide with peak oviposition periods. © 2022 Society of Chemical Industry.

Entomopathogens and Parasitoids Allied in Biocontrol: A Systematic Review

“…Trichogramma pretiosum [ 24 , 47 , 52 ] and E. formosa [ 29 , 38 , 40 , 51 ] were the most researched parasitoids, followed by A. colemani [ 23 , 30 , 32 , 35 , 46 ], C. flavipes [ 55 , 58 ], and Diaeretiella rapae [ 18 , 43 ]. In terms of microorganisms, B. bassiana [ 17 , 18 , 24 , 26 , 32 , 33 , 35 , 40 , 42 , 43 , 48 , 51 , 52 , 54 , 55 , 57 , 58 , 59 , 60 , 61 , 63 , 64 , 65 ] was the most studied fungus, followed by M. anisopliae [ 30 , 34 , 36 , 37 , 48 , 49 , 50 , 51 , 53 , 55 , 57 , <...…”

“…Thirty-eight out of forty-nine combinations of biocontrol agents were reported as compatible [ 18 , 19 , 20 , 22 , 24 , 25 , 26 , 29 , 32 , 34 , 35 , 36 , 37 , 39 , 41 , 43 , 44 , 45 , 47 , 49 , 50 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 62 , 63 , 64 , 65 ] ( Table 1 ). Six combinations were reported as incompatible [ 17 , 27 , 28 , 42 , 51 ], often due to a lower emergence rate caused either by bad timing, direct infection, or too high dosage.…”

“…The influences of combined biocontrol agents on pest mortality were analysed in ten laboratory experiments extracted from nine studies [ 25 , 28 , 38 , 44 , 45 , 50 , 57 , 62 , 65 ]. Out of 41 observations made in these experiments, 14 reported a positive effect, with significantly higher pest mortality when biocontrol agents were combined compared to the strongest agent used alone.…”

“…Out of 41 observations made in these experiments, 14 reported a positive effect, with significantly higher pest mortality when biocontrol agents were combined compared to the strongest agent used alone. In 11 of these, the interaction was less than additive [ 25 , 28 , 57 , 65 ]. In two further observations, it was additive [ 50 ], and in one, it was synergistic [ 50 ].…”

“…We used Citavi software (version 6.11.0.0) to import the included studies. We extracted data on (1) pest, (2) control agents, (3) crop, (4) location, (5) study design, (6) evolution of pest and biocontrol agent populations, (7) crop damage, (8) crop yield, and (9) compatibility of biocontrol agents from the 49 selected articles [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. Each combination of biocontrol agents was considered an experiment, leading to 1...…”