Resistance of The Spiny Bollworm Earias Insulana (Boisd.) To Some Pesticides

Exposure of the first instar larvae of the spiny bollworm, Earias insulana (Boisd.); obtained from a collected field populations, to selection pressure with the synthetic pyrethroid lambda-cyhalothrin for thirteen generations under laboratory controlled conditions resulted in a resistant strain with ca. 145-fold of resistance. Development of resistance was weak and slow during the first four generations (RR was ca. 3-fold) after which a gradual increase in development of resistance took place during the following eight generations. The susceptibility of the different larval instars of lambda-cyhalothrin-selected strain was decreased as the larvae grown older. The obtained resistant strain exhibited a wide range of cross resistance to eight insecticides belonging to different groups of chemicals, namely: conventional, developmental and bioinsecticides; cross resistance ratios ranged between 0.87 to 25.7-fold. Using of the synergist piperonyl butoxide suppressed the level of resistance in lambda-cyhalothrin-resistant individuals. Resistance was accompanied with some changes in majority of the inspected biological aspects; resistance resulted in elongation of the larval and pupal stages, simultaneously, with a reduction in the reproductive potential of the emerged adults. So, it could be concluded that selection with lambda-cyhalothrin was unfavorable for the selected insects.