The Diamondback Moth (DBM) is an important brassica pest and is controlled by several types of insecticides. On some occasions, the fields are sprayed two-four times per week without success. Sometimes this occurs because ineffective insecticides are used. Works showed that laboratory tests using the recommended field rate of insecticides can detect the ineffective ones. Here, we collected DBM larvae and pupae from the States of Ceará (Tianguá), Minas Gerais (Barroso), Bahia (Mucugê), Mato Grosso (Sinop) and the Federal District (Brazlândia and Embrapa Hortaliças). We reared the populations in the laboratory and larvae of the first laboratory generation were treated with the recommended field rate of abamectin, acephate, B. thuringiensis, cartap, chlorfluazuron, deltamethrin, and spinosad. We previously determined that an effective insecticide should cause more than 90% larval mortality. Insecticide effectiveness was different from field to field. Spinosad killed 100% of larvae; acephate, B. thuringiensis and cartap killed less than 90% of the larvae in Tianguá; abamectin and chlorfluazuron did not control the insect in Brazlândia and Mucugê respectively. Deltamethrin was inneffective in all areas tested. Diamondback Moth populations were resistant to one or more active ingredients and programmes to manage insecticide resistance must be implemented in Brazil.
Plutella xylostella; cabbage; chemical control; insecticide resistance
