Impacto de acaricidas sobre a resposta funcional e numérica do predador Amblyseius largoensis alimentado com Raoiella indica

Abstract

The suppression of the population of any pest by a predator depends on two basic components of the prey-predator interaction: the functional response and the numerical response of the predator. Such responses can be affected by several factors, such as exposure to acaricides. In the present study, the effects of the acaricides abamectin, azadirachtin, fenpyroximate and chlorfenapyr on the functional and numerical responses of the predatory mite Amblyseius largoensis, an important natural enemy of the pest mite Raoiella indica, were investigated. Amblyseius largoensis exhibited a type II functional response when fed with eggs of R. indica, the type of functional response not being altered by exposure to acaricides. Despite not changing the type of functional response, exposure to abamectin resulted in a decrease in the average number of prey consumed per predator. Exposure to acaricides increased prey handling time by A. largoensis by 67%, 25%, 38% and 35% for abamectin, azadirachtin, fenpyroximate and chlorfenapyr, respectively. Exposure to abamectin reduced the attack rate of A. largoensis by 52%. The numerical response of A. largoensis was affected only by exposure to abamectin, where only 60% of the females ovipositioned and regardless of the density of prey offered, the average number of eggs/female/day was always less than 0.36. The efficiency of feed to biomass conversion of A. largoensis eggs decreased with increasing prey densities, and this trend was not altered by exposure to acaricides. Despite not changing the trend of efficiency of conversion of food into egg biomass, exposure to abamectin drastically compromised the oviposition of A. largoensis, not being observed an increase in egg production with the increase in prey density.