Author : Barroga, Salud F.

Summary : Plutella populations were collected from 12 vegetable areas in the Philippines and mass-reared in the laboratory. Three species of parasites, Microplitis sp., Apanteles sp., Nythobia plutellae (Vicreck), and two viral diseases, nuclear polyhedrosis and granulosis were observed from field-collected larvae during the laboratory rearing. The resistance of the 12 plutella populations to DDT and to five organophosphorus insecticides using third instar larvae were detected by paper impregnation method. To confirm the resistance, a topical toxicity test was conducted and the median lethal doses (LD 50) were determined by probit analysis. As shown by the resistance factor (RF), the College and Kanlaon were 9.74 x and 13.18 x resistant to DDT, respectively. The resistant factor of the other populations to DDT ranged from 26.22 to 397.26. All the populations exhibited marked resistance to methyl parathion and to malathion with an RF ranging from 247.34 to 1753.39 and 17.82 to 822.34, respectively.