Susceptibility of Nilaparvata lugens (Hemipteran: Delphacidae) populations in the Philippines to insecticides

Development of field resistance among Asian brown planthopper populations to insecticides contributes significantly towards the overall problem caused by the brown planthopper in rice production. We evaluated the susceptibility of brown planthoppers collected in the Philippines to the insecticides imidacloprid, fipronil and fenobucarb insecticides. Additionally we documented the changes in the populations' susceptibilities to the same insecticides when reared in insecticide-free environments. We found that brown planthopper populations collected in the Philippines between 2009 and 2010 were relatively susceptible to the tested insecticides when compared to historical data. Our findings provide baseline data for future studies. We also found that in populations characterized by high initial susceptibility to insecticides, the continued absence of insecticide selection pressure generally resulted in a slight decrease or no change in the populations' insecticide susceptibility.