The resistance of the lady beetle, Eriopis connexa, to lambda-cyhalothrin enhance tolerance to other pyrethroids

Integration of predators and insecticides for pest control in agroecosystems has been a core component of integrated pest management, but it has rarely been achieved due to obvious incompatibilities. Some form of obtaining integration is improving the ecological and physiological selectivity for pest management purpose. The ecological selectivity deals with forms of reducing the contact of the insecticide with the natural enemy; while the physiological selectivity refers to characteristics exhibited by the natural enemy resulting in less toxicity of the insecticide to the natural enemy compared to the target pest such as natural enemies exhibiting resistance to the insecticide. Pyrethroid insecticides are widely recommended to control insect defoliators but lack efficacy against sucking sap insects such as aphids. In fact, aphid outbreak is commonly reported after pyrethroid sprays. Thus, the conservation of aphid predators is important to pest management in agroecosystem requiring pyrethroid sprays to control defoliator insects. The lady beetle, Eriopis connexa (Germar), is a predator of soft-bodied arthropod but mainly found associated to aphid infestations in row, vegetable and fruit crops. In our studies we found that the resistant population (R) of E. connexa to λ-cyhalothrin was also highly tolerant to other pyrethroids when exposed to dried residues and topical treatments of the recommended field rates compared to the susceptible population (S). Among the eight-tested pyrethroids (ζ-cypermethrin, bifenthrin, deltamethrin, esfenvarelate, fenpropathrin, α-cypermethrin, permethrin, and λ-cyhalothrin) the survival of the S-population for larvae (10 to 96.7%) and for adults (0 to 86.6%) were significantly lower compared to survival obtained to the R-population for larvae (73.3 to 100%) and for adults (56.7 to 100%) exposed to dried residues. Likewise, the survival of the S-population for larvae (0 to 63.3%) and for adults (0 to 26.7%) were also significantly lower compared to the survival obtained to the R-population for larvae (80 to 100%), and for adults (50 to 100%) exposed to topical treatment. Among the tested insecticides, the fenpropathrin and bifenthrin were the least and most toxic product across the developmental stage and populations of E. connexa. The gain in survival by being resistant to λ-cyhalothrin based on the survival difference (% survival of the R-population - % survival of the S-population) across all tested pyrethroids varied from 3 to 63% for larvae and from 3 to 70% for adults exposed to dried residues, and from 36 to 96% for larvae and from 21 to 82% for adults exposed to topical treatment. These results indicate that despite the variation among the pyrethroids such as type I and II, their formulations, field rates recommended, and target pest species, there are high survival response of the R-population beetles to pyrethroids allowing us to recommend one, if necessary, with low impact.