Abstract
The farmer interest in biological control-based management practices using entomopathogenic fungi (EPF) for the control of many economically important insects has increased. In this process, selection of effective strains of EPF is an important criterion to control the target insect pests in efficient manner. In this context, this research work was formulated to find out environmentally effective strains of EPF in the soils of costal districts of Andhra Pradesh, India. Out of 135 soil samples collected, 9 yielded 9 strains of Lecanicillium lecanii. Among all 9 L. lecanii isolates, the least median lethal concentration (LC50) for 3rd instar larvae of the tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), was 1.17 × 106 spores ml−1 in L-8, followed by 1.27 × 106 spores ml−1 in L-5 in an increasing order. Likewise, the median lethal time (LT50) values of different isolates of EPF against the 3rd instar of S. litura were calculated for the uniform highest concentration of 1 × 108 spores ml−1. Among all 9 L. lecanii isolates, the lowest median lethal time (LT50) was observed as 7.70 days by L-8, followed by 7.77 days by L-5 and 8.50 days by L-7.
Highlights
Fungi are the most important component in most of the soil microbiota
Soil acts as main reservoir for the entomopathogenic fungi (EPF) as it protects the EPF from the degradation by sunlight
Biological control method is recommended to reduce insect population below the economic threshold level (ETL)
Summary
Fungi are the most important component in most of the soil microbiota. Soil acts as main reservoir for the entomopathogenic fungi (EPF) as it protects the EPF from the degradation by sunlight. Since soil is a natural habitat for EPF, isolation of EPF involves soil sampling. Soil factors such as pH, EC, organic contents, ecosystems, and other biotic components can affect EPF activity and persistence. Knowledge of local species composition and distribution is important, if the indigenous populations of EPF in the soil are to be managed in ways to facilitate the control of pest insect populations within the agro-ecosystem (Meyling and Eilenberg 2007). Zimmermann (1986) proposed the “insect bait method” (in vivo) for the isolation of entomogenous fungi from soil, which allows investigations on spectrum composition and frequency of these insect pathogens in soil habitat as compared to the selective medium method (in vitro) (Korosi et al 2019). The “insect bait method” has been widely used for isolating EPF from soils in different parts of the world (Deaver et al 2019)
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