Differential susceptibilities of Brontispa longissima (Coleoptera: Hispidae) to insecticides in Southeast Asia.

To present the susceptibility of Brontispa longissima (Gestro) (Coleoptera: Hispidae) to insecticides, 22 populations were collected in Southeast Asia from 2007 to 2010. Moreover, the laboratory susceptible strain was maintained. The results demonstrated that the lethal concentration50 value of the susceptible strain to avermectin, beta-cypermethrin, and acetamiprid was 0.034, 0.024, and 1.843 mg liter(-1), respectively. Compared with the susceptible strain, 10 populations developed a medium level of resistance to avermectin (10.8-fold < resistance ratio [RR] < 34.7-fold) and 11 populations had low or minor resistance (3.6-fold < RR < 9.6-fold), only one population from Qionghai still remained susceptible (RR = 2.04-fold). The Zhangjiang population expressed high resistance (RR = 46.1-fold), five populations expressed medium resistance (10.6-fold < RR < 18.1-fold), and 12 populations had low resistance (5.36-fold < RR < 9.66-fold) for beta-cypermethrin, only four populations maintained low resistance or susceptibility (2.08-fold < RR< 3.49-fold). All populations were susceptible to acetamiprid (1.65-fold < RR < 2.89-fold), except for the Jakarta population that developed minor resistance (4.33-fold). This study shows that the resistance to beta-cypermethrin and avermectin in B. longissima is widespread. However, most populations remain susceptible to acetamiprid. Acetamiprid may be considered an available option for the control of B. longissima and should be considered when designing pest management programs.