Inseticidas utilizados no controle de pragas do algodoeiro são seletivos para Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)?

Abstract

In integrated pest management programs (IPM) of the cotton crop, the joint use of several control methods is advocated. In this crop, the boll weevil stands out as the main pest, since it causes expressive losses in yield and demands a great deal of applications of insecticides for its control which in general causes biological disequilibrium. A strategy to reduce those disequilibriums is the use of selective compounds. Thus, the present work is intended to evaluate the effects of six insecticides registered in MAPA for control of Anthonomus grandis over Harmonia axyridis under laboratory conditions. Eggs, third instar larvae, pupae and adults of H. axyridis were treated with the products ethiprole, etofenprox, lambdacyhalothrin, lambdacyhalothrin + chlorantraniliprole, pymetrozine and thiamethoxam + chlorantraniliprole via spraying in Potter tower, wich were applied at their highest concentrations recommended for the boll weevil control. After they were treated, the insects were maintained under controlled conditions of 24±2ºC, RH of 70±10% and photoperiod of 12:12 (L:D) and fed eggs of Ephestia kuehniella ad libitum. The completely randomized design with five replications was utilized, consisting of either eight insects or fourteen eggs. It was found that the predator in its initial developmental stages (eggs and larvae) was more sensitive to the insecticides, followed by the pupa and adult stages. The insecticide ethiprole was the only that caused no lethal effect to the predator in any developmental stage; however, it provoked some sublethal effects when applied on its eggs (reduction of the larval stage and of the reproduction). Lambdacyhalothrin caused high mortality of the predator in all the developmental stages which were exposed to the product. Due the low toxicity presented by the insecticide ethiprole, this compound must be prioritized in IPM programs in the cotton crop aiming at the preservation of the ladybug H. axyridis. The other insecticides must be evaluated under semi-field and field conditions for the confirmation of the toxicity to that predator.