Biopriming of broad bean seeds with entomopathogenic fungus Metarhizium robertsii does not affect invertebrate communities of the agroecosystem

Abstract

Biopriming, or treatment of seeds with beneficial microorganisms such as beneficial fungi, can be a promising strategy in agricultural cultivation. However, the effects of such treatment on non-target organisms living in the soil and on plants have not been sufficiently studied, and it is not known very well whether such treatment would alter invertebrate communities (e.g., harm them). Here, we addressed the effect of treating broad bean seeds (Vicia faba L.) with the conidia of entomopathogenic ascomycete Metarhizium robertsii on the diversity and abundance of invertebrate communities in the agroecosystem in the south part of West Siberia in 2019 and 2020. We have analyzed the effect both on the general invertebrate communities as well as on the main pests of beans. In the case of bean pests, we assessed the rate of plant infestation by aphids (Hemiptera: Aphididae) and the degree of leaf damage by leafminer flies Liriomyza bryoniae (Diptera: Agromyzidae). In most cases, the treatment did not lead to significant changes in the total abundance of the soil invertebrates and herbivores or the abundance of predominant taxa (Coleoptera: Carabidae, Staphylinidae, Elateridae, Scarabaeidae, Curculionidae; Hemiptera: Miridae, Cicadellidae, Aphididae; larvae of Diptera). A positive effect of treatment on population density of the soil mesofauna was noted for Diptera larvae in June 2019. Regarding aphids and leafminer flies, no significant effect was observed in terms of the proportion of plants with aphids and the density of aphid colonies on individual plants throughout the season, and no significant influence was found on the proportion of plant leaves damaged by leafminer fly Liriomyza bryoniae larvae. In summary, in Western Siberia, the treatment of broad bean seeds with M. robertsii did not significantly affect non-target arthropods common for bean fields as well as the main pests of beans, namely aphids and miner flies.