Stability and realized heritability of resistance to imidacloprid in the field- collected brown planthopper Nilaparvata lugens (Hemiptera: Delphacidae) from Lampung, Indonesia

Availability of rice throughout the year in the Indonesian field makes the brown planthopper, ( Nilaparvata lugens ) (Stål) an important pest. Imidacloprid is an insecticide active ingredient that is commonly used for managing N. lugens populations. The data on resistance stability and realized heritability would be effective to derive a viable resistance management system against N. lugens . The resistance ratio (RR) increased after selection for five generations, from 52.36 to 180.46-fold in N. lugens collected from rice fields in the District of Central Lampung, Lampung Province, Indonesia. In order to determine the stability of resistance, five additional generations (totaling ten generations) were reared without insecticides exposure. Stability experiments revealed that resistance to imidacloprid was unstable and there was a loss of resistance from 180.46 to 39.46-fold over ten generation without any selections (DR value = -0.07). On the contrary, the resulting resistance level after continues selections with imidacloprid during the subsequent three generations might be up the resistance level from 180.46 to 235.93-fold. The realized heritability values ( h ² ) of imidacloprid resistance were low at 0.1465 and 0.1348 in five and eight generations that were selected, respectively. This unstable resistance could be mitigated by temporarily removing selection pressure or by rotating to insecticides with different mode of actions. Having a low heritability of resistance, the sustainable wide-range resistance management plan will be required in controlling the N. lugens population in Indonesia.