Compatibility of Metarhizium anisopliae and Beauveria bassiana with insecticides and fungicides used in macadamia production in Australia

Abstract

Background Integrating fungal biocontrol agents into crop protection programs dominated by synthetic pesticides is an important first step towards developing an integrated pest management (IPM) program; however, their successful integration relies on an understanding of how their performance may be impacted by the remaining agrochemicals deployed for managing other pests and diseases. In this study we tested 10 formulated pesticides used in macadamia production at different concentrations to determine their effects on the germination, mycelial growth and sporulation of Metarhizium anisopliae and Beauveria bassiana in vitro. Further tests with laboratory‐grade actives of the noncompatible pesticides were conducted to determine whether any antagonistic effects were caused by the active constituent or by formulation additives. Results At their registered concentrations, formulated trichlorfon, acephate and indoxacarb were compatible with M. anisopliae, whereas B. bassiana showed compatibility with formulated trichlorfon, acephate, indoxacarb, sulfoxaflor and spinetoram. Bioassays using laboratory‐grade active constituents indicated that the adverse impact of formulated beta‐cyfluthrin on both fungal species and that of formulated methidathion on B. bassiana is probably due to components of the emulsifiable concentrate formulations rather than their active constituents. Diazinon was the only insecticidal active that showed high toxicity to both fungal species. The two fungicides, carbendazim and pyraclostrobin, were toxic to both fungal species at all tested concentrations. Conclusion Our results identify which pesticides used on macadamias in Australia are compatible and incompatible with entomopathogenic fungi. Future studies on pesticide degradation rates will help define the spray intervals required to eliminate these adverse effects.

Transmission of Metarhizium anisopliae and Beauveria bassiana to adults of Kuschelorhynchus macadamiae (Coleoptera: Curculionidae) from infected adults and conidiated cadavers

“…These strains have been lodged in the Queensland Plant Pathology Herbarium, Department of Agriculture and Fisheries, Brisbane, with accession numbers BRIP 70,272 (ECS1) and BRIP 70,267 (B27). Strain ECS1 was cultured on sterile Sabouraud dextrose agar supplemented with 1% (w/v) yeast extract (SDAY) 49 and strain B27 was cultured on sterile malt extract agar (MEA) media 49 . All fungal strains were incubated in the dark at 25 ± 1 °C for 15 days before harvesting the conidia for experimentation.…”

Interactions of fungal entomopathogens with synthetic insecticides for the control of Kuschelorhynchusmacadamiae (Coleoptera: Curculionidae)

“…The formulation additives for these insecticides included toluene and xylene‐type aromatic solvents, which were toxic to the EPF. Our previous in vitro study examining the effects of beta‐cyfluthrin and methidathion in EC and non‐EC formulations also showed that beta‐cyfluthrin at 12.5 mg AI/L and methidathion at 250 mg AI/L without EC formulation additives were compatible with M. anisopliae strain QS155 and B. bassiana strain B50 but when EC formulations were tested at the same active ingredient concentrations they were toxic to both fungal species (Khun et al., 2021a).…”

“…Our previous in vitro study examining the effects of the insecticides acephate and indoxacarb at concentrations between 6.25% and 100% of their respective FFCs showed that these insecticides had no detrimental effect on the conidial germination, growth and sporulation of M. anisopliae strain QS155 or B. bassiana strain B50 (Khun et al., 2021a). In this study, both insecticides were mixed directly with M. anisopliae strain ECS1 and B. bassiana strain B27 in order to simulate a tank mixture for orchard spraying.…”

“…In line with the Australian macadamia industry's commitment to reducing the use of broad‐spectrum chemicals and integrating biological control agents into pest management practices (AMS, 2019), the aim of this study was to determine the feasibility of combining EPF with insecticides (acephate and indoxacarb) currently used for K. macadamiae control. Because B. bassiana strain B50 and M. anisopliae strain QS155 were compatible with acephate and indoxacarb in our previous in vitro study (Khun et al., 2021a), we hypothesized that these insecticides would not have any inhibitory effect on the germination and growth of B27 and ECS1 when prepared and applied as spray mixtures on K. macadamiae and consequently, the combined insecticide/EPF applications would be expected to improve the efficacy of K. macadamiae management in commercial macadamia orchards.…”

Efeito de fungicidas ao fungo entomopatogênico Metarhizium rileyi

“…Assim, as interações, principalmente as negativas, devem ser consideradas nos programas de Manejo Integrado de Pragas (MIP), pois, quanto mais seletivo e compatível for o produto químico mais eficiente será a conservação do entomopatógeno (Silva et al, 2005). Este aspecto é mais importante em agroecossistemas onde o fungo entomopatogênico é um importante fator para a redução populacional de insetos pragas, sendo considerado um inimigo natural-chave (Khun et al, 2021).…”