Susceptibility of Chrysoperla externa eggs (Neuroptera: Chrisopidae) to conventional and biorational insecticides.

Chrysoperla externa (Hagen) is a generalist predator in agroecosystems. We assessed the effect of cypermethrin, endosulfan, methoxyfenozide, and spinosad on immature development time, survivorship, sex ratio, fecundity, and fertility on this organism in laboratory toxicity tests. Effects on second-generation organisms were also studied. Exposures were realized by dipping </=24-h-old eggs in pesticide solutions at maximum field recommended concentrations (MFRCs) registered in Argentina. Although no significant ovicidal effect was detected with any of the compounds, endosulfan and cypermethrin produced 96 and 100% mortality, respectively, on larvae 48 h after hatching. Spinosad caused significantly higher mortality than controls but this effect was less immediate, lasted longer and was less intense than effects with conventional insecticides. Methoxifenozide did not produce significant mortality in any stages. Spinosad and cypermethrin reduced egg development time, but no similar effects were observed with other insecticides. Methoxyfenozide inhibited the fecundity during the first 24 h; however, fertility was not affected. Spinosad had no effect on fecundity or fertility of the adults. No long-term detrimental effects on the progeny were detected for spinosad and methoxyfenozide. Conventional insecticides (endosulfan and cypermethrin) were more toxic than biorationals ones when applied to eggs of C. externa. The ecotoxicological studies showed the neonate-L(1) larvae as a susceptible developmental stage. These data indicate that the biorational insecticides tested are compatible with conserving C. externa.