Selective application of malathion: effect on boll weevil, non-target insects and natural enemies.

Background: Non-selective chemical insecticides are the main method to manage the major insect pest of cotton in the Americas, the boll weevil Anthonomus grandis (Boheman, 1843) (Coleoptera: Curculionidae). The objective was to evaluate the effect of selective application of malathion on the boll weevil and non-target insects and natural enemies. The experimental design was in randomized blocks with the treatments control, without spraying (T1) and with all cotton plants in the rows sprayed, sequentially, after the appearance of cotton squares or all (T3) or alternated (T4), respectively, when the number of them with cotton squares with oviposition punctures by the boll weevil reached 10%. Spraying was done with malathion (1,000 g.i.a. L-1). The insecticide malathion sprayed on alternate rows of cotton is as effective in controlling the boll weevil as when sprayed on all rows. However, this insecticide applied to alternate rows controls aphid populations because it is ecologically selective to the parasitoid B. vulgaris and the predators, Coccinellidae, Syrphidae, and Araneae.