In recent years, biological methods have been used widely for controlling stem-boring pests in forests. In this study, the larvae of Xylotrechus rusticus (L.) (Coleoptera: Cerambycidae) were infected with 4 strains of 2 species of Beauveria (Hypocreales: Cordycipitaceae). Larval detoxifying and protective enzyme activities were measured at different times after infection. The results showed significant differences in the pathogenicity of the 4 strains. The most virulent strain, Beauveria bassiana (Bals.-Criv) Vuill. strain BbCC01, caused 93.3% mortality, with an estimated LT50 of 4.69 d. The detoxifying and protective enzyme activities in larvae infected with strain BbCC01 changed significantly. To resist the infection, the activities of the detoxifying enzymes (carboxylesterase, glutathione S-transferase, and acetylcholinesterase) first increased and then slowly decreased. The activities of the protective enzymes (catalase, superoxide dismutase, and peroxidase) showed a similar trend. The enzyme activities peaked at 72 to 96 h post-infection. In this study, the B. bassiana strain BbCC01 proved to exhibit high virulence towards X. rusticus larvae. This research provides important information regarding the biological control of X. rusticus and elucidates the patterns of detoxifying and protective enzyme activities in the susceptible larvae.
Jinfeng Hu,Feng Chen,Jun Wang,Wenhua Rao,Lei Lin,Guocheng Fan
The green peach aphid,Myzus persicae(Sulzer) (Hemiptera: Aphididae), is an economically devastating crop pest worldwide. TheM. persicae(SEF-R) population of a cabbage field in China was tested for susceptibilities to 13 insecticides. Compared with the susceptible population (FFJ-S), extremely high and high resistance to beta-cypermethrin (324-fold) and imidacloprid (106.9-fold) was detected in SEF-R. More importantly, this is the first report of resistance in the fieldM. persicaepopulation to sulfoxaflor (32.4-fold), flupyradifurone (9.5-fold), pymetrozine (34.8-fold), spirotetramat (8.1-fold), flonicamid (5.8-fold), and broflanilide (15.8-fold) in China when compared with FFJ-S. The resistance factor decayed to a low level to sulfoxaflor and pymetrozine after 15 generations without any selection pressure. The resistance-related mutations (R81T and kdr) detected in SEF indicated target-site resistance to neonicotinoids and pyrethroids, respectively. Biochemical assays revealed the involvement of monooxygenase, carboxylesterase, superoxide dismutase, and peroxidase in a multi-insecticide resistance mechanism. The overexpression of P450s, esterases, and a UDP-glycosyltransferase might be responsible for the multi-insecticide resistance in SEF-R. The knockdown of CYP6CY3 in SEF-R increased its susceptibility to imidacloprid, thiacloprid, and thiamethoxam, which verified that P450s play vital roles in neonicotinoid metabolism. Our findings provide guidance for the rational use of insecticides to delay resistance development in GPA.Keywords:Myzus persicae;insecticides;resistance monitoring;detoxification enzymes;protective enzymes;metabolic mechanism
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