Selectivity assessment of chlorfenvinphos reevaluated by including physiological and behavioral effects on an important beneficial insect.

ABSTRACT

Selectivity is an important factor in identifying candidate pesticides to be used in crop protection since it characterizes chemicals that, while being effective against target pests, exert an acceptable impact on the other components of the environment. Extrapolated to an integrated pest management (IPM) context, selectivity implies that candidate pesticides may preserve the ability of beneficial insects to significantly control target pest populations. In the present study, we assess the physiological selectivity of the organophosphate chlorfenvinphos, used to protect cruciferous crops against the cabbage root fly, Delia radicum (Diptera Anthomyiidae), by investigating both the lethal and sublethal effects exerted on its main parasitoid Trybliographa rapae (Hymenoptera Figitidae). The comparison of the median lethal doses showed that T. rapae was at least seven times less sensitive than D. radicum to chlorfenvinphos. However, longevity of parasitoids surviving a sublethal dose was reduced by half. The potential fecundity of females was decreased by 9.6 to 22.8%. Chlorfenvinphos also induced important behavioral changes in both sexes and reduced the chances for parasitoids to mate by more than 70%. While most behavioral changes were reversible, effects on mating and on fecundity were not, thereby suggesting long-term effects on the reproduction of the parasitoid. These cumulative effects of chlorfenvinphos would have dramatic consequences on the efficacy of parasitoids contacting such doses of chlorfenvinphos in the field and therefore there is question about the intrinsic selectivity of this insecticide.