The Diamondback Moth (Plutella xylostella) is the most important cabbage pest in the Federal District. New insecticides are frequently tested for its control and in this study two new Bacillus thuringiensis formulations [B. thuringiensis var. aizawai (350 and 500 g/ha) and B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai (350 and 500 ml/ha)] were tested between May and October 1995. The insecticides B. thuringiensis var. kurstaki (500 ml/ha), deltamethrin (240 ml/ha) and an untreated check were also included in the experiment. A randomized block, with seven treatments and four replications was used. The results showed that B. thuringiensis var. aizawai at the two dosages and B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai at a dosage of 500 ml/ha were the most efficient products. After the end of the field experiment, Diamondback Moth larvae and pupae were collected from the experimental area. The insects were reared in the laboratory and second instar larvae from the first generation were fed with leaf discs treated with the B. thuringiensis dosages used in the field experiment. All products caused more than 97% larval mortality. The laboratory test suggests that the reduced efficiency of B. thuringiensis var. kurstaki (500 ml/ha) and B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai (350 ml/ha) in the field test may be due to the poor persistence of the products in the environment.
Brassica oleracea var. capitata; chemical control; Diamondback Moth; Plutella xylostella; Bacillus thuringiensis
