Research of three insecticides' residual effect on oriental fruit moth and peach fruit moth

【Objective】The oriental fruit moth(Grapholitha molesta Busck) and peach fruit moth(Carposina niponensis Wals.) are two major pests that damage deciduous fruit trees in China. Their larva mainly bore apple, pear, peach, apricot, plum, hawthorn and Chinese jujube, resulting in fruit rotting and dropping,and severely affect production and quality. Moreover, the oriental fruit moth damages new shoots of various fruit trees, and inhibits shoot growth and flower bud formation. In recent years, severe outbreaks of some fruit tree pests happened because of the improvement of fruit production efficiency, the increase of cultivated species and area, mixing planting of different fruit trees and the prohibition of high toxic and long residue insecticides. Currently, the main methods to control these two pests are trapping at the adult stage and spraying at the egg and mature larvae stage. Technology of sex pheromone trapping and mating disruption succeeded. But chemical control is still involved in finding new high efficient, low toxic and low-residue insecticides. Flubendiamide and chlorantraniliprole are two diamide insecticides produced in the early of this century, which have special insecticidal mechanism and long residual activity, and beable to control many Lepidoptera pests with a low toxicity to bees and fish. They have been used to control various vegetable and fruit tree pests. Chlorbenzuron is a traditional and biorational insecticide controlling Lepidoptera pests, and has some biological activities on the egg, larva, pupa and adult. In order to gain better understanding of the direct lethality of chlorantraniliprole, flubendiamide and chlorbenzuron on the oriental fruit moth and peach fruit moth, and their influence on all stages' development, we used different doses of three insecticides respectively to treat the egg and larvae of oriental fruit moth and peach fruit moth.【Methods】Oriental fruit moth and peach fruit moth were used as experimental insects,and‘Fuji'apples were immersed in different doses of flubendiamide, chlorantraniliprole and chlorbenzuron respectively for 5 s, naturally dried and then the eggs of oriental fruit moth and peach fruit moth were laid on the fruits. Five eggs were on each apple with 9 times of repeat, and distillated water was used as control. Fuirts were placed in a digital light illumination incubator with T=(24±1) ℃, L∶D =16∶8h, RH=(60±10)%. The number of egg hatching was checked 5 days after incubation, the larvae survival number was checked 10 days after incubation, and the egg hatchability, larval mortality and ratio of survival larvae and egg were calculated. Further more, the immersion method was also used to treat the mature 20 larvae of each insect with 3 times of repeat. The number of larvae mortality, pupation, eclosion and oviposition were checked everyday to evaluate three insecticides' direct lethal effects on these two pests and their influence on all stages' development.【Results】After treating apples with three insecticides, observe the influence of residual chemicals on egg hatching. Compared with control, flubendiamide(200 mg·kg-1) and chlorantraniliprole(50 mg·kg-1, 25 mg·kg-1) significantly reduced egg hatchability of oriental fruit moth by 13.33%, 11.11% and 11.11%, respectively. Various concentrations of three insecticides significantly caused high mortality of the newly-hatched larvae. All three insecticides had no obvious effect on egg hatching of peach fruit moth, but various concentrations of flubendiamide and chlorbenzuron significantly increased the mortality of the newly-hatched larvae. Chlorantraniliprole reduced pupation rate, adult eclosion rate of the oriental fruit moth, and also inhibited egg hatching of F1 generation.Chlorbenzuron only affected the primary generation's development and had no influence on F1generation's egg hatching. All the doses except chlorantraniliprole 25 mg·kg-1inhibited the pupating of peach fruit moth. All the doses significantly inhibited adult eclosion and oviposition of peach fruit moth, and peach fruit moth treated with flubendiamide 200 mg·kg-1, chlorbenzuron 200 mg·kg-1and 100 mg·kg-1lost fecundity. The results suggested that it would be better to use flubendiamide 200 mg · kg- 1and chlorantraniliprole 50 mg·kg-1, 25 mg·kg-1at the egg hatching stage and the chlorantraniliprole 50 mg·kg-1at the mature larvae emerging from fruit to control the oriental fruit moth, and use the flubendiamide 200mg·kg-1, 100 mg·kg-1, 67 mg·kg-1and chlorbenzuron 200 mg·kg-1at the egg hatching stage and flubendiamide 200 mg·kg-1and chlorbenzuron 200 mg·kg-1, 100 mg·kg-1at the mature larvae emerging from fruit stage to control peach fruit moth.【Conclusion】When using these three insecticides to control oriental fruit moth and peach fruit moth in production, it's better to spray at egg stage and mature larvae emerging from fruit stage to control the pests which had high activity to newly-hatched larvae and the succeeding stage of mature larvae.