Effect evaluation of 6 insecticides on Anomala corpulenta

Abstract:【Objective】The Anomala corpulenta Motschulsky is a major pest that damages deciduous fruits and forest trees in China, mainly in the adult and larvae stages. The adulta hide during the day, damage the plants during the night, their adaptability is very strong, due to the adults mainly appearing after the rain. If it is not controlled in time, the fruit tree could be damaged severely, especially for newly planted seedlings of apple, walnuts, cherries and other fruit trees. The adults lay their eggs in the soil near the roots of the host plants. Currently, the main methods to control these pests are spraying the insecticides on the host leaves in the adult stage and irrigating the host roots with the insecticides in the egg and larvae stages. The top five single chemical pesticides of domestic registration for controlling the A. corpulenta are chlorpyrifos, phoxim, fipronil, imidacloprid and isofenphos-methyl, accounting for 88.7% of the registered chemical pesticides. But according to China's latest pesticide restriction list, fipronil and isofenphosmethyl has been banned for use on fruit trees. Currently, controlling the A. corpulenta often requires using chlorpyrifos and phoxim, and the control effects are relatively high. However, due to these two kinds of insecticides having a long-term and excessive usage, many areas appear to have a status of resistance being increased and control effects being reduced. Therefore, we need to choose new insecticides to provide bet-ter control. In order to gain a better understanding of the effects of sulfoxaflor, chlorantraniliprole, fluben-diamide and chlorbenzuron on adult, egg and newly hatched larvae of A. corpulenta, and to provide the ba-sis for reasonable control of A. corpulenta, we carried out the following laboratory experiment.【Methods】We used six insecticides, by applying the leaf dipping method, to treat the adults, 15 of each sample, re-peated 3 times, then placed in a rearing room with T=(24±1)℃, RH=(60±10)% and carried out the shad-ing treatment, investigated the mortality of 1, 3, 5 and 7 days after treatment, and the regression analysismethod was used to deal with the data of 6 different kinds of insecticides, and then we calculated the LT50 and LT95values. We also used different doses of six insecticides respectively to treat the egg using the leafdipping method, impregnation method and insect dipping method, and investigated the number of egghatchings and newly hatched larvae deaths.【Results】The effects of the six insecticides for the A. corpulenta adult in descending order were: chlorpyrifos>phoxim>chlorantraniliprole>flubendiamide>sulfoxa-flor>chlorbenzuron. The ready availability of chlorpyrifos 400 mg·L^-1 and 1 600 mg·L^-1 were the best,with the adult mortality rate being 100.00% at 1 DAT(days after treatment), significantly higher than theother five types of insecticide-treated, showed better rapid availability and controlling effect, and the LT50 and LT95values were less than 1 day. The adult mortality of phoxim and chlorantraniliprole began to in-crease at 3 DAT, reached more than 80.00% at 5 DAT, and rose to more than 93.33% at 7 DAT, the con-trolling effect had no significant differences with chlorpyrifos. The adult mortality rate of flubendiamide,sulfoxaflor and chlorbenzuron were poor. The effect of six insecticides for the egg hatching rates in de-scending order were: chlorpyrifos>phoxim>flubendiamide>chlorbenzuron>chlorantraniliprole>sulf-oxaflor, and for newly hatched larvae the death rates were: chlorantraniliprole>chlorpyrifos>sulfoxa-flor>phoxim>chlorbenzuron>flubendiamide. Compared with the control, various concentrations of thesix insecticides significantly caused high mortality in the eggs and newly hatched larvae. The controllingeffects of four concentrations of chlorpyrifos were more than 97.78%, followed by chlorantraniliprole,which were more than 93.33%. Based on the above results, we conclude that we can use the chlorpyrifos,phoxim and chlorantraniliprole on the occurrence period of the adults and the chlorpyrifos and chlorantra-niliprole on the occurrence period of the eggs and first stage larvae to prevent A. corpulenta. The chloran-traniliprole can be used as a new insecticide to control the A. corpulenta at the different stages.【Conclusion】To sum up, we can spray the chlorpyrifos 400 mg·L^-1, phoxim 400 mg·L^-1 and chlorantraniliprole175 mg·L^-1 on the occurrence period of the adults of A. corpulenta, which can effectively control the harmand achieve good control effects. On the occurrence period of the eggs and first stage larvae of A. corpulenta, the chlorpyrifos 200-400 mg·L^-1, chlorantraniliprole 87.5-175 mg·L^-1 and phoxim 200-400 mg·L^-1 can effectively control the hatching of the eggs and prevent the harm of first stage larvae.