Repeated exposure to abamectin and amitraz causes multigenerational fitness suppression in the predatory mite Neoseiulus longispinosus (Acari: Phytoseiidae)

Repeated exposure of natural enemies to pesticides may induce cumulative physiological stress across generations, potentially altering their performance and diminishing their effectiveness in biological control programs. This study evaluated the multigenerational effects of two commonly used acaricides, abamectin and amitraz, on the development, reproduction and population growth of the predatory mite Neoseiulus longispinosus. Developmental duration, survival, reproductive traits and life table parameters were evaluated in the progeny of adult females from the first (G1), third (G3) and fifth (G5) generations under multigenerational exposure to the acaricides. Both acaricides significantly reduced immature survival and prolonged development compared with controls. Substantial reproductive impairment was observed, reflected by shortened oviposition periods, reduced female longevity and decreased total egg production. Life table analysis showed significant declines in net reproductive rate (Ro) and intrinsic rate of increase (rm), with rm decreasing from 0.297 females/female/day in the G1 control to 0.225 and 0.217 in G5 abamectin- and amitraz-treated mites, respectively. These results demonstrate strong multigenerational suppression of fitness in N. longispinosus, highlighting the need to incorporate long-term acaricide impacts into ecological risk assessments and integrated pest management programs.