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To evaluate the influence of different host plants including apple, wild jujube, jujube, pear and hawthorn on the cold-tolerance substances in overwintering larvae of the peach fruit moth Carposina sasakii Matsumura, we measured the larvae super-cooling capacity, the water content (W), total fat content (TFC), total protein content (TPC) and total glycogen content (TGC) in the body. Results showed that the mean super-cooling point (SCPs) and freezing point (FPs) of overwintering larvae from the 5 host plant fruits differed significantly, ranging from -15.53 to -8.50 degrees C and -11.31 to -4.04 degrees C, respectively. The overwintering larvae fed on hawthorn owned the highest SCP, FP, TGC and the lowest W, while those fed on apple had the lowest SCP, FP, TFC and TGC but the highest W and TPC. The fresh mass (FM) of the overwintering larvae fed on pear was the highest, while those fed on jujube was very low. Those fed on jujube accumulated the highest TFC but the lowest TPC.

To understand the resistance risks of Frankliniella occidentalis Pergande against phoxim, this paper studied the resistance mechanisms of phoxim-resistant F. occidentalis population against phoxim and the cross-resistance of the population against other insecticides. The phoxim-resistant population had medium level cross-resistance to chlorpyrifos, lambda-cyhalothrin, and methomyl, low level cross-resistance to chlorfenapyr, imidacloprid, emamectin-benzoate, and spinosad, but no cross-resistance to acetamiprid and abamectin. The synergists piperonyl butoxide (PBO), s, s, s-tributyl phosphorotrithioate (DEF), and triphenyl phosphate (TPP) had significant synergism (P < 0.05) on the toxicity of phoxim to the resistant (XK), field (BJ), and susceptible (S) populations, while diethyl maleate (DEM) had no significant synergism to XK and S populations but had significant synergism to BJ population. As compared with S population, the XK and BJ populations had significantly increased activities of mixed-functional oxidases P450 (2.79-fold and 1.48-fold), b, (2.88-fold and 1.88-fold), O-demethylase (2.60-fold and 1.68-fold), and carboxylesterase (2.02-fold and 1.61-fold, respectively), and XK population had a significantly increased acetylcholine esterase activity (3.10-fold). Both XK and BJ population had an increased activity of glutathione S-transferases (1.11-fold and 1.20-fold, respectively), but the increment was not significant. The increased detoxification enzymes activities in F. occidentalis could play an important role in the resistance of the plant against phoxim.