Avaliação da viabilidade e infectividade de nematoides entomopatogênicos após exposição a diferentes concentrações de produto à base de óleo de neem (Azadirachta indica)

Abstract

Including those that act as pests in agricultural crops. Their use may offer an alternative to the current excessive use of chemical products. Similarly, plant-based insecticides are also regarded as efficient tools for pest control. In this context, studies that investigate the combination of non-chemical control agents — such as botanical insecticides and entomopathogenic nematodes — have the potential to transform the pesticide market. The objective with this study was to evaluate if different concentrations of a commercial neem oil-based product affect the viability and infectivity of infective juveniles (IJs) of nematodes. Three experiments were conducted in a completely randomized design with five replicates per treatment. In each replicate, 5,000 IJs from two isolates were used: '25-6' (Oscheius tipulae) and 'UENP6' (Heterorhabditis amazonensis). For the '25-6' isolate, two experiments were carried out with different neem oil concentrations: 0%, 5%, 25%, 50% in the first experiment, and 0%, 50%, 100%, and 200% in the second, with the control treatment consisting of distilled water. In the third experiment, conducted with the 'UENP6' isolate, concentrations of 0%, 50%, 100%, and 200% were tested. Assumptions of normality and homoscedasticity of the data were evaluated using the Shapiro-Wilk and Bartlett tests, respectively. The results of the viability and infectivity were subjected to analysis of variance, and the means were compared using Tukey's test at a 5% significance. All analyses were performed using R software. The results showed that both nematode species lost viability and infectivity after exposure to the botanical insecticide based on neem oil. The O. tipulae isolate exhibited incompatibility with the product at concentrations of 5%, 25%, 50%, 100%, and 200%. Similarly, the H. amazonensis isolate was incompatible at concentrations of 50%, 100%, and 200%.