The Diamondback moth (DBM) Plutella xylostella (Lepidoptera: Yponomeutidae) is the most important insect pest of cabbage in Brazil, which is controlled through pesticides sprays, that have adverse effects on the parasitoid natural population. In the last few years, new active ingredients were launched in the market, bringing the need to evaluate their agronomical efficiency and impact on natural enemies. An experiment was set up from June to October 2001, at Embrapa Hortaliças (Brazil), using the cabbage cultivar "Kenzan". The treatments were sprayed weekly, during eight weeks, starting when cabbage heads were being formed (about four weeks after transplanting). Five plants in each plot were sampled each week and the number of holes and larvae in the four central leaves in each cabbage head were recorded. The number of holes and larvae also were recorded for the whole cabbage plant. Every 15 days, larvae were collected from the plant and taken to the laboratory for parasitism evaluation. At the harvest, cabbage heads were evaluated regarding their commercial value, established based on a scale of grades and percent of commercial heads, besides counting the number of holes and larvae located at the cabbage head and in the whole plant. Among the pesticides tested, Spinosad, Indoxacarb and B. thuringiensis var. kurstaki were the most efficient in DBM control and did not differ from each other in all the parameters evaluated, and these products provided cabbage heads with great commercial value. The pesticides Thiacloprid and a strain of B.T. S764 (Embrapa) were not efficient. However, B. thuringiensis var. kurstaki reunited efficiency of control and low impact in the population of parasitoid. The pesticide Spinosad caused impact in the parasitoid population in the larvae of DBM located in the cabbage head. The most frequent parasitoid collected in the experimental area were Diadegma leontiniae; Apanteles sp.; Actia sp. and Oomyzus sokolowskii.
Plutella xylostella; cabbage; natural enemies; chemical control
