ABSTRACT
The residual action of the insecticides imidacloprid/Beta-cyfluthrin, clothianidin and chlorfenapyr was evaluated in regard to third-instar larvae and adults of the predator Cycloneda sanguinea (Linnaeus). Cotton seeds of the cultivar BRS IPÊ were sowed in PVC pots and the plants were maintained in the greenhouse. Upon reaching 25 days of age, the plants were sprayed with the lowest dosages of the products recommended by the manufacturers, using a manual sprayer. The insecticides evaluated in g a.i.L-1 of water were imidacloprid/Beta-cyfluthrin (Imidacloprido/Beta-ciflutrina 100/12.5 CS – 0.25/0.03), clothianidin (Clotianidina 500 WP – 0.33) and chlorfenapyr (Clorfenapir 240 CS0.80). Distilled water was used as a control. Previously marked leaves, from each treatment, were removed from the plants and taken to the laboratory where they were placed in Petri dishes containing bacteriologic agar solution. Eggs of Anagasta kuehniella (Zeller) were placed on cotton leaves following the release of a Trichogramma specimen per dish after 1, 12, 23 and 35 days from pesticides application. Each Petri dish was immediately closed with plastic PVC film. A completely randomized experimental design was used, with 4 treatments and 12 replicates, each one formed by 3 third-instar larvae or 1 couple of adults. The number of dead larvae and adults in each treatment was examined 12, 24 and 48 hours after exposure to the chemicals. The products were classified according to categories proposed by the International Organization for Biological Control (IOBC). All the compounds tested were evaluated as class 4 = persistent, causing mortality above 30% up to 31 days after application on cotton leaves.
KEY WORDS
Cotton; natural enemy; pesticides; selectivity
