The Occurrence Dynamics And Damage Of Three Fruit Borers And Cold Tolerance Of Grapholita Molesta (Busck) (Lepidoptera: Tortricidae)

1 Studies on the occurrence dynamic, damage of fruit borer in Feicheng monoculture peach orchard and polyculture peach orchard of TaianThe population danamics and damages of the fruit borer insect pests were investigated in monoculture peach orchard and polyculture peach orchard of Feicheng and Taian district in Shandong Province. The results showed that the three main borer insect pests, Carposina sasakii (Matsmura), Dichocrocis punctiferalis (Guenee) and Grapholita molesta (Busck) in monoculture peach orchard had two, three, and five generations in 2009, respectively, and two, three, and four generations in 2010, respectively. The percentages of shoot tip damage in young and old peach orchard were different, but there was no significant difference between them. In polyculture peach orchard, in 2009 and 2010, C. sasakii (Matsmura), D. punctiferalis (Guenee) and G. molesta (Busck) had two, three, and five generations in each year, respectively. The percentage of shoot tip damage in May was lower than June and July. All of the borers had the phenomenon of generation overlapping in monoculture peach orchard and polyculture peach orchard, and G. molesta (Busck) had the largest population and made the most serious damage to the Feicheng peach productions.2 Seasonal variation in cold tolerance of the Grapholita molesta (Busck) (Lepidoptera: Tortricidae) larvaeIn this study, seasonal variation in cold tolerance of G. Molesta (Busck) were investigated by measuring their super-cooling point (SCP), water content, total lipid content and cold survival ability. Results showed that cold tolerance of the larvae varied obviously with seasons. The pre-winter larvae had higher tolerance to low temperature than the summer larvae. The SCP, the water, protein and glycogen content of the larvae varied remarkably in different seasons. The SCP of the larvae were lowest in January(–25.66℃and–19.92℃, respectively) while highest in July (–15.91℃and–11.97℃, respectively); the water, the protein and the glycogen contents of larvae were highest in July(70.62%, 158μg/mg, 26.29μg/mg, respectively), while lowest in January(55.20%, 62μg/mg, 9.32μg/mg), and then increased after winter. The lipid contents of the larvae were 9.34%(July);then increased to 33.35% ( October ), and then to 16.48%. 3 Rapid cold hardening of Grapholita molesta (Busck) larvaeThe larvae of G. molesta (Busck), were treated for 2 h in the laboratory under the temperature 5℃(LT1) and 0℃(LT2) , respectively. The super-cooling point, the rates of water, the fat, protein, and glycogen content of the larvae after low temperature treatment were determined , respectively. The results showed that the super-cooling point of the larvae reduced by low temperature, but there was no significant difference. The rates of water and lipid in the larvae also increased, and also there was no significant difference . The protein and glycogen contents in the larvae reduced. It was that low temperature treatment could increase the cold tolerance in the G. molesta larvae in some ways.