Effect Of Volatile In Migratory Between Peach Trees And Pear Trees And Management Threshold Of Oriental Fruit Moth

The oriental fruit moth, Grapholita molesta, is a globally important insect pest. In China,the moth widely distribute in all of the fruit producing areas except Tibet. The host of the moth includes many fruit trees belong to the family Rosacaae. The larvae infest shoots and fruits of peach, apple, pear, and plum et al. In China, the laevae feed shoots of peach in early growing season, shift to infest to pear fruits at the later growing season, and the companion planting area of fruit trees was the most serious. Volatiles from peach and pear in different season were collected and identified by dynamic headspace absorption method and GC-MS,the EAG responses of the moth to several compound of volatiles and the development and fecundity performance of the moth reared on shoots and fruits of peach and pear in different seasons conducted in laboratory condition, and control index based on number of adults captured by sex pheromone traps was studied based on investigation in field. Main results of this study are as follows.1. Collected and identified volatiles from peach and pear in different season by dynamic headspace absorption method and GC-MS. The results showed that the kinds and contents of the volatile compounds emitted from peach and pear in different season were different. 38 compounds were detected in peach and 47 compounds in pear. Z-3- hexene acetate was detected and the contect was higher in all samples except of volatile emitted from peach twigs with flowers. Farnesene was contected in all of the samples, but different sample contain types and contents of farnesene were different. Benzaldehyde can be detected in peach volatiles of the early growing season, decreased or undetected in later growing season; but in pear volatiles, benzaldehyde can be detected in mid-August. That was consistent with the migratory of the moth.2. Electroantennogram responses of the oriental fruit moth to 13 host volatile compounds were conducted. Results showed that the EAG value of the moth were relate to type and concentration of compound, gender of adult, and the mating status of female. The EAG was increased with the increasing concentration of the compound. The EAG of male to the middle concentration(0.01-10μg/μL) of Z-3-hexene acetate and low concentration(0.001-10μg/μL)of Hexyl acetate were higher than female. The EAG of female to low concentration(0.001,0.01 and 0.1μg/μL) of methylis salicylas, high concentration(1,10,100μg/μL) of heptanal andα-pinene, benzaldehyde were higher than male. The EAG of the 4th day mated female to0.001-1μg/μL benzaldehyde were higher than unmated female. EAG of adult to all concentration of α-pinene were lower. The EAG of the moth to green leaf volatiles, such as Z-3-hexene acetate, hexyl acetate, trans-2-Hexenal were higher.3.The results showed that development time, survivorship, and fecundity of the moth were signicantly different on shoots and fruits of peach and pear under laboratory conditions.The moth developed faster on shoots and fruits of peach, compared with pear. The preimaginal survival rate was the highest on peach shoots while it was found that the moth could not survive on pear fruit collected on 10 of May. The boring rates of neonatal larvae were higher on shoots than on fruits and the rate value presented higher with the longer delay in the collecting time for pear fruits. Pupal weights of female were significantly higher on fruits than those on shoots. Fecundity were significantly less on pear shoots than those on the other host plants collected at different time. The net reproductive rate( R0) and intrinsic rate of natural increase( rm) was highest on peach shoot, and lowest on pear shoot. Cluster analysis of the life table parameters of the moth on shoots and fruits of peach and pear cut at various times of the growing season indicated that peach fruit picked at 10 May, pear shoot,pear fruit picked at 15 June and 15 July were unsuitable host to the pest, and peach shoot,peach fruit picked at 15 June, pear fruit picked at 15 August were suitable host to the peat.Therefore, it is concluded that the switch of the moth from peach orchard to pear orchard related to different performance because different diet that the larvae feed on, and volatile blends emitted by host plant in process of host location.4. Results showed that the number of egg lay on middle of torso of fruit was the highest.Percent of fruit with egg and number of eggs per 100 fruits increased with the increasing of diameter of fruit. Percent of fruit with eggs and number of egg per 100 fruits all were significant correlation with number of moth traped by sex pheromone lure, and the relation was logarithmic. The management threshold based on percent of fruit with eggs or number of egg per 100 fruits could transformate into the the management threshold based on number of moth traped by sex pheromone lure. If taken 1% of fruit with egg and 1 egg per 100 fruits as the management threshold, which was 2.27 and 2.32 based on number of G. molesta traped by sex pheromone lure, respectively. If taken 2% of fruit with egg and 2 eggs per 100 fruits as the management threshold, which was 2.61 and 2.58, respectively.