Vitality and Stability of Insecticide Resistance in Adult Propylaea japonica (Coleoptera: Coccinellidae)

Propylaea japonica (Thunberg) was a dominant species among the predacious ladybirds in the fields and active from March to November during a year in Fuzhou, China. Stability of insecticide resistance and vitality in adult P. japonica were investigated. The field ladybird P. japonica in Fuzhou, China, showed 9- to 16-fold resistance ratios to chlorpyrifos, 13- to 2,083-fold to methamidophos, 32- to 230-fold to fenvalerate, and 4- to 49-fold to avermectins, respectively, based on the field monitoring during 2004, 2009, and 2012, as compared with insecticide-susceptible F(39) progenies. The resistance levels in the field P. japonica were high during May and November but low during summer. The population growth tendency index in field P. japonica was 0.8-fold as high as that in insecticide-susceptible P. japonica. The field P. japonica also showed high tolerance to the insecticide as compared with pest Lipaphis erysimi Kaltenbach and two parasitoids Diaeretiella rapae and Pachyneuron aphidis. Stable insecticide resistance levels and high vitality were found first in adult P. japonica with 1-, 30-, or 60-d-old adults, or among the adults developed form the eggs produced by newly emerged adults or by 60-d-old adults. Increased activity of glutathione S-transferases, carboxylesterases, and cytochrome P450 monooxygenases might be involved in the resistance of P. japonica. The results indicated that, in certain areas, inclusion of P. japonica for pest control in the integrated pest management would be highly recommended.