Methodological Approaches to the Assessment of the Entomopathogenic Activity of Microorganisms Against Insect Pests in Vitro (Review)

Abstract

Excessive application of chemical insecticides in agriculture has led to some serious problems that threaten the environment and human health. One of the possible ways to overcome the situation is to shift to environmentally-friendly preparations based on entomopathogenic bioagents. The purpose of this review was to search for and systematize methodological approaches to determine the entomopathogenic activity of microorganisms of various taxonomic groups in laboratory conditions. The expediency of choosing the necessary method when studying a particular phenomenon or process is an important point both in the fundamental and applied field of research. The primary assessment of the entomopathogenic activity of microorganisms in vitro is the basis for expanding the spectrum of their action, introducing new strains into collections. It also contributes to the replenishment of knowledge about the already known properties of various types of microorganisms. All this, certainly, is connected with the further choice of them as biological agents. Each of the presented groups of entomopathogens has its distinctive features of the mechanisms of action determined by the target insect. Concerning the choice of methodological approaches for assessing the entomopathogenic effect of fungi, the authors relied on the physiological characteristics of the insect and its stage of harmfulness. The researchers were guided by methodological approaches of oral infection of insects using an infected food source to study the activity of bacterial strains. Pathological changes in the cellular structure, as well as deformations of intestinal elements, were noted. The most common way to assess the effect of entomopathogenic viruses in the laboratory is the method of surface infection of the food source of the tested insect, taking into account the high specialization of the agent. When studying the mechanisms of action of fungal, bacterial and viral agents, researchers injected a suspension of the pathogen into the insect’s body. The search and systematization of relevant methodological approaches to assess entomopathogenic microorganisms depending on the taxonomic affiliation is an important part of the work directly related to the development of a high-quality and effective bioinsecticide.