Diapause Regulation Of Macrocentrus Cingulum,and Its Application For Control Of The Asian Corn Borer Ostrinia Furnacalis (Guenée)

The Asian corn borer(ACB),Ostrinia furnacalis(Guenée)is the main insect pest of corn in China.Biological control is one of the important measures to control ACB.The Macrocentrus cingulum(Brischke)is an excellent endoparasitic wasp of ACB larvae.which has the potential for suppressing the ACB population.Therefore,the ACB used as a host for rearing of M.cingulum were mainly studied.Selection of geographical populations of the M.cingulum with good parasitizing capacity for ACB larvae,the functional response of M.cingulum to ACB larvae,field cage experiment by releasing M.cingulum for ACB control and the diapause induced condition and low temperature storage of M.cingulum.The main results are as follows:There were significant differences in the parasitic number per female,oviposition duration and sex ratio(?:?)of different geographical populations.The Shenyang population had the largest parasitic number per female,reaching 30.7,followed by the Gongzhuling and Songyuan;the populations of Zhaodong and Changtu had the smaller parasitic number which were about 16.5 and 22.6.The Changtu population had the largest oviposition period,lasting for 10.2 days,followed by Qiqihar and Shenyang,and the populations of Heihe and Zhaodong had the smaller oviposition period which were about only about 6.2 and 4.4 days.The sex ratio of Shenyang population was the smallest,only 30%,the rest of the populations were more than 45%.There were no significant differences among the female longevity,emergence number per O.furnacalis larva of next generation of M.cingulum,emergence number of next generation per female of M.cingulum,the emergence rate of offspring,and the cocoon weight of offspring.In summary,the Gongzhuling,Songyuan and Qiqihar populations of M.cingulum were the good candidates for ACB control.M.cingulum was a typical low temperature and short-day diapause type insect.When the temperature was 21?,the photoperiod was 10 L:14 D,the diapause rate could reach 99%.When the temperature was 21?during the day,15?at night and the photoperiod was 10 L:14 D,the diapause rate could reach 100%.The optimum storage temperature was 4?.The female longevity and parasitic number showed no significant differences between adults emerged from the diapause ACB stored at 4?for 60~90 days and those from the ACB without cold storage,and the emergence rate were above 90%.When the M.cingulum was fed at 28?during diapause termination,the period from treatment to the first mature larvae emergence was about 8 days and the emergency duration was about 6~8 days.The results showed that the functional response of M.cingulum fitted Holling type II model in the range of 20?~32?.The parasitic number of ACB larvae by M.cingulum increased with the increasing of the densities of host at the same temperature.But when the host density increased to a certain amount,the parasitic number tends to be stable.The parasitic efficiency was the largest at 24?,reaching 23.22 and the lowest was 15.84 at 20?.According to the maximum parasitized hosts and parasitic efficiency,24?is the suitable activity temperature of M.cingulum.The searching efficiency of M.cingulum decreased with the increasing density of O.furnacalis and M.cingulum.Using the Hassell model,we found the searching coefficient Q and the disturbance coefficient was maximum at 28?and minimum at 20?,respectively,the interference between the M.cingulum weakened the parasitic function.In field cage experiment,when the release number of M.cingulum was 7.5 pairs/m~2,the parasitic rate was significantly higher than the other treatments,reaching 61.75%,and the number of larvae,the number of holes and the length of tunnel were significantly lower than the control and the treatment of 5 pairs/m~2,which was about 1.4 head/plant,2.5 pcs/plant and6.41cm/plant,respectively.When the release number was 2.5 pairs/m~2 and 5 pairs/m~2,separately,there were no significant differences between all the evaluation indexes;and except that the parasitic rate was significantly lower than that in control,the other indicators showed no significantly different than those in the control.When the release amount was 7.5pairs/m~2,although the number of larvae and the number of holes were not significantly different from the treatment of 2.5 pairs/m~2,they were still smaller than this treatment.