| The silverleaf whitefly,Bemisia tabaci?Gennnadius?,is an important invading pest of vegetable and ornamental crops and causing serious damages to agricultural production in the world,the usual treatment method of controlling B.tabaci presently is the application of chemical pesticides,which leads to incrementally insecticide-resistance developing of B.tabaci.But excessive spray brings many severe problems which harms human health,contaminates environments and damages the ecosystem.Therefore,it is very important to take biological control to B.tabaci as dominant means,agricultural control as its basis.Then,selecting effective natural enemies to establish a biocontrol system of controlling B.tabaci is significant.The technique of rapidly mass-reared Aleuroglyphus ovatus?Troupeau?,screening of artificial diets and cold storage technique of Neoseiulus cucumeris?Oudermans?were studied in the thesis.In addition,the functional response,searching behavior,interference response and interspecific competition,intraguild predation of N.cucumeris were discussed,and the combined control effect of N.cucumeris and Er.hayati to B.tabaci had been evaluated in laboratory and field conditions.The research contents and results were listed as follows:1.To meet with quantity production requirement of A.ovatus as prerequisite,with the reproduction rate of A.ovatus in and per unit of time and weight as standard,the optimum formula of mass-reared A.ovatus was studied,which was consist of 80%wheat bran,10%maize bran,5%yeast powder,3%wheat germ flour and 2%sugar.As mass-reared A.ovatus with the formula fodder,the population density in per germ fodder increased quickly in 10 to 30 days,and reached the peak?8713.33/g?in the 30th day at 28±1?,RH80±5%and L0:D24.The result showed that formula B was suitable for A.ovatus mass-reared under laboratory conditions.2.In order to find the artificial diets to replace A.ovatus to breed N.cucumeris,different artificial diets were studied at 26±1?,RH70±5%and 16L:8D.The animal protein diet?AD1?,which was consist of10 g pupal tissue fluids of Chinese oak silkworm?Antheraea pernyi?,5 g yeast extract powder,5 g tryptone,5 g glucose,5 g honey,10 g fresh egg yolk and 60 g distilled water,is the optimal artificial diet to rear N.cucumeris under labortary conditions.The predatory mite could finish the development stages and take 6.4days to complete a lifecycle which was longer than feeding A.ovatus?6.0 days?.The total egg number per female mite,egg number of a day per female mite and the intrinsic rate of increase were 27.9 egg/female,1.3 egg/day/female and 0.1573,respectively.All of these were lower than feeding on A.ovatus,which were34.7 egg/female,1.5 egg/day/female and 0.1875,respectively.The result showed that AD1 is suited to rear N.cucumeris in laboratory conditions.Effects of low temperature and storage time on reproductive capacity and surivival rate were studied,which results showed that female adult N.cucumeris were kept in6?and 8?for four weeks,which had a higher survival rate?>65%?and egg number of a day per female?>1 egg/day/female?.3.The type of functional responses of N.cucumeris to B.tabaci and the functional responses equation were determined by Juliano's logisitic regression system?2001?for the fisrt time.The results showed that the N.cucumeris preferred to prey egg and young stages of B.tabaci,and all of the functional responses followed the Type II models?Holling II?.The N.cucumeris did not prey 4th-instar nymph and adult of B.tabaci,and their prey capacity were as follows:female adult,deutonymph,male adult and pretonymph.The female adult N.cucumeris was the best predator stage,which mean daily consumption on egg,1st-instar,2ed-instar and 3rd-instar were 8.5,5.2,3.0 and 2.1,respectively.The functional responses equations of female N.cucumeris to egg and 1st-instar to 3rd-instar nymph were Na=N0[1-exp?0.0980Na-0.0378T?],Na=N0[1-exp?0.0997Na-0.0230T?],Na=N0[1-exp?0.1407Na-0.0186T?]and Na=N0[1-exp?0.0986Na-0.0096T?],respectively;attack coefficients were 0.0378,0.0230,00186 and 0.0096,respectively;handling times were2.5939,4.335,7.5653 and 10.2699 h,respectively.All these equations indicated a higher value of attack coefficient and a lower value of handling time for female adult as compared to immature stages and male adult.Therefore,searching efficiency decreased with the age increasing of B.tabaci in the same host density,and the searching efficiency of female adult N.cucumeris to B.tabaci egg was the highest in laboratory conditions?28±1?,RH70±5%and 16L:8D?.The intraspecific interference of N.cucumeris was heighten with its density increasing.The intraspecific interference model of female and male adult N.cucumeris were E=0.0955P-0.057400.05740 and E=0.0675P-0.4928,and the relation equations of competition intensity and host density were I=0.0545+0.717lgP and I=0.0438+0.6659lgP,respectively.4.To determine the effect of host resources availability on interspecific interaction of N.cucumeris and Er.hayati,the interspecific competitive interaction between N.cucumeris and Er.hayati were studied in different host densities and mixed stages host.In single-and mixed-instar nymph tests,significant differences in host-feeding capacities were found among all treatments.N.cucumeris combined with Er.hayati in control B.tabaci which exhibited superior capacity of host-feeding compared to the other treatments.In the mixed-instar experiments,N.cucumeris combined with Er.hayati showed a clear preference for feeding on younger hosts?1st-and 2nd-instar nymph?,and total killed of B.tabaci were higher.The results showed that N.cucumeris and Er.hayati could balance their respective advantage of predation and parasitism to get the best control effect.The leaf discs experiments showed that it was no different in prey consumption of N.cucumeris between parasitism and healthy nymphs in a same host density,and the prey behavior of N.cucumeris on B.tabaci nymphs were random.For the 1st-instar,N.cucumeris female adults had higher prey consumption for to healthy nymph of B.tabaci than the parasite nymphs,and showed preference for healthy 1st-instar with host density increased.5.The combined control efficiency of releasing N.cucumeris and Er.hayati to control B.tabaci were studied under laboratory and field conditions.The results showed that N.cucumeris and Er.hayati could coexist in a biological control system of B.tabaci,and had certain inhibitory effect on the population dynamics of B.tabaci.Laboratory mini-cages experiments showed that the control efficiency of N.cucumeris and Er.hayati increased with their released densities increasing,N.cucumeris and Er.hayati were released together which could effective for decreasing the number of eggs and nymphs of B.tabaci,which were 88.53%and 97.5%in 30th day respectively.Field-cage evaluations exhibited that the control efficiency of combined releasing was higher than single-releasing,and control the efficient of combined releasing to adult B.tabaci was 84.68%in 30th day.Combined-releasing of two times had significant control effect on B.tabaci,and the control efficiency were more than 30%in 10th day after twice released. |
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