Combined Application Of Pyemotes Zhonghuajia (Prostigmata:Pyemotidae) And Entomogenous Fungi For The Control Of Phthorimaea Operculella (Lepidoptera:Gelechiidae)

The potato tuber moth,Phthorimaea operculella（Zeller）（Lepidoptera,Gelechiidae）is one of the most important potato pests in the world because of its wide distribution and serious harm to the development of potato industry.Pyemotes zhonghuajia Yu,Zhang&He（Prostigmata:Pyemotidae）is an ectoparasitic mite with great potential in controlling many species pests of Lepidoptera,Coleoptera,and Homoptera,and it can kill pests 640,000 times than own weight.Combined application of natural enemy mites and entomogenous fungi to control pests is a great significance in the field of biological control.The compatibility and synergistic effect of entomogenous fungi on natural enemy mites are the key points worth paying attention to in the process of combined application.In this study,we tested the lethal and sublethal effects of P.zhonghuajia and entomogenous fungi on P.operculella.And under the precondition of the safety evaluation of entomogenous fungi on P.zhonghuajia,we tested and compared the control effect of entomogenous fungi combined with P.zhonghuajia and P.zhonghuajia on P.operculella inside potato tubers.This study provided a theoretical basis for the effective use of the P.zhonghuajia and entomogenic fungi to control P.operculella.The main results are as follows:1.Lethal and sublethal effects of P.zhonghuajia on P.operculellaOur results showed that the cumulative death rate of 100 P.operculella eggs againsted by 100 P.zhonghuajia within 5 days was 61.80±1.54%.The death rate of a single P.zhonghuajia against the single 4th instar larva of P.operculella within 24 h was 95.00±5.00%.When the density of P.zhonghuajia was more than 3,the death rate of the 4 th instar larva of P.operculella was 100%within 72 h.When the density of P.zhonghuajia was 20,the death rate of one pupa of P.operculella within 72 h was90.00±5.77%.The first to third instar larvae of P.operculella were killed in 23.46 min,and the fourth instar larvae were killed in 2076.00 min.P.zhonghuajia short-term parasitism（30 min,60 min）on 4th instar larvae of P.operculella had significantly extended the pupa stage and preadult stage of female P.operculella,and significantly reduced the adults Longevity,APOP,oviposition days and mean fecundity of female adult.The r_m,R₀ andλof the population of P.operculella were significantly decreased,and T was significantly higher than that in the control group.2.Control effect and sublethal effect of P.zhonghuajia on P.operculella inside potato tubersOur results showed that when the density of P.zhonghuajia was more than 40,the amount of pupae inside single potato tuber was significantly reduced,and the emergence rate was slightly decreased but not significantly.P.zhonghuajia had significantly reduced the amount of pupae in all treatment groups in five kilo potato tubers,and the emergence rate of P.operculella was significantly decreased when the density of P.zhonghuajia was 100.The weight of single potato tuber and the number of dung piles on single potato tuber and five kilo potato tubers were also significantly affected by high density of P.zhonghuajia.The results of sublethal effect on the F₁generation of P.operculella showed that when the density of P.zhonghuajia was 100,the egg stage,preadult stage and adults longevity of P.operculella were significantly decreased.When the density of cattails was more than 40,the larvae stage,preadult stage and oviposition period of female were significantly decreased.The mean fecundity in all treatment groups was significantly lower than that in the control group.The r_m,R₀,T andλof P.operculella population decreased with the increase of the density of P.zhonghuajia.The T decreased significantly when the density of P.zhonghuajia was more than 40,and the r_m andλdecreased significantly when the density of P.zhonghuajia was 100.3.Lethal and sublethal effects of entomogenous fungi on P.operculellaOur results showed that entomogenous fungi KY1136 and KY1115 had great lethal effects on the eggs,fourth instar larvae and pupae of P.operculella,the corrected mortality rates were 61.67±5.78%,88.33±3.33%,98.33±2.89%and 61.67±23.6%,73.33±4.41%,81.67±7.64%,respectively.LC₅₀ of entomogenous fungi KY1136 and KY1115 on P.operculella eggs were 1.9x10⁶ and 0.9x10⁷,respectively.The results of sublethal effects of entomogenic fungi KY1136 and KY1115 on P.operculella showed that KY1136 and KY1115 could significantly prolong the larval stage,preadult stage of male and female of P.operculella,while the adults longevity of male and female and the APOP,oviposition days and mean fecundity of female adults decreased significantly.The r_m,R₀,λand GRR（Gross reproductive rate）of P.operculella population decreased significantly.4.Safety evaluation of entomogenous fungi on P.zhonghuajia and combined application of P.zhonghuajia and entomogenous fungi against P.operculellaThe results of the safety evaluation of entomogenous fungi KY1136 and KY1115against P.zhonghuajia showed that KY1136 and KY1115 had no obvious toxicity to P.zhonghuajia,its had no significant effect on the mortality of P.zhonghuajia.and the reproduction of single P.zhonghuajia.The pupation amount of combined application of P.zhonghuajia and entomogenous fungi group was significantly lower than that of P.zhonghuajia group,and the number of dung piles on potato tuber was slightly decreased but not significantly compared with that of P.zhonghuajia group,and the weight of potatoes in 100 P.zhonghuajia with high concentration KY1136 group was greater than that in 100 P.zhonghuajia group.and it had no significant difference with the group without P.operculella.