CONICET | Buscador de Institutos y Recursos Humanos

The generalist predator Chrysoperla externa (Neuroptera: Chrysopidae) presents a strong potential as a biological control agent due to its easily rearing, high voracity and tolerance to several pesticides. This specie is distributed in the Neotropical Region, associates to several crops, among them vegetal ones and preying on several relevant pests such as aphids, whiteflies, trips and various lepidopterans. In Argentina an indiscriminate chemical control with broad spectrum pesticides is still the first option for controlling pests that at the same time cause resistance problems and reduction of beneficial organisms. Therefore, it would be desirable that predators or parasitoids develop tolerance or resistance as phytophagous pests for their maintenance in the agricultural ecosystems. The objective of this work was to evaluate the tolerance of C. externa to the pyrethroid cypermethrin by topical exposure in laboratory conditions. The endpoints evaluated were: mortality at 24 h post-treatment, intoxication and recovery after treatment through behavioral parameters such as tremors, knockdown effect, inability to walk due to being glued and the response to the stimulation. It had been evaluated six different concentrations of the pesticide including the full field one and the exposure method was by topical applications on third larval instar. The concentrations were 7,5 mg/L a.i., 10 mg/L a.i., 12,5 mg/L a.i., 25 mg/L a.i., 37,5 mg/L a.i. and 50 mg/L a.i. of cypermethrin and the observations were done between 24 h to 96 h after insecticide exposition. It was observed a low mortality of larvae at 24 h post-treatment even at the highest concentration evaluated. The most of treated organisms look normal at 24 h post-treatment and those who were affected showing a knockdown effect had a complete recovery from 48 to 72 h post-treatment. According to these preliminar results, C. externa has demonstrated a hight tolerance capacity to pyrethroids probably due to a higher metabolism of chemical molecule by detoxification enzymes such as esterases and mixed-function oxydases, a rapid excretion via the feces or a lower target sensitivity. Future studies should be addressed at molecular level to complete our knowledge on this predator about biological aspects at biochemical and physiological level for its further use in biological control of pest programs where the use of conventional insecticides is needed yet to maintain the pests under economic injury level.