Effects Of Pesticide Resistant Spodoptera Exigua On Parasitism Characters Of The Parasitoid Meteorus Pulchricornis(Hymenoptera:Braconidae)

Chemical and biological control are of two approaches in Integrated Pest Management(IPM).The challenges facing IPM are coordinating these two approaches to obtain a positive control effect.Beet armyworm Spodoptera exigua(Hubner)(Lepidoptera,Noctuidae)is a polyphagous pest,attacking as many as 138 plant species from 108 genus of 35 families,including with 28 crops and 32 vegetables.Extensive applications of pesticides have caused resistance problems,which compromise once effective insecticides for beet armyworm.Biological control at this juncture attracts our attention.The parasitoid of the beet armyworm,Meteorus pulchricornis(Wesmael,1835)is of important natural enemies.To enhance the parasitoid in biological control of the pest,this thesis studied the effect of resistant beet armyworm host on developmental performances of M.pulchricornis.The results provide data for effective coordination of chemical control and biological control in IPM of the beet army worm.1.Effects of pesticide resistant S.exigua larvae on larval growth and developmentof M.pulchricornisEmamectin Benzoate resistant(two levels)Spodoptera exigua larvae were exposed to parasitism by M.pulchricornis females,with susceptible host larvae as the controls.Development time,pupal weight and duration were measured and compared between resistant and susceptible hosts.Egg-to-pupa duration of offspring parasitoids showed a first-increasing-then-decreasing trend across increasing resistant levels of S.exigua.The egg-to-pupa duration 7.93 d in a moderately resistant host,prolonged by 5.3%compared to that in a susceptible host(7.53 d),and shortened by 12.0%compared to that(6.63 d)in a highly resistant host.Pupa body weight of offspring parasitoids showed a linear downward trend across resistant levels of S.exigua.Pupa body weight in a moderately resistant host was 9.04 mg,shortened by 6.3%compared with the control(9.60 mg),and by 8.30%compared to that(8.80 mg)in a highly resistant host.Pupa-to-adult duration of offspring parasitoids showed a first-increasing-then-decreasing trend across resistant levels of S.exigua.Pupa-to-adult duration(6.80 d)from attacking moderately resistant hosts,prolonged by 5.6%of that(6.43d)from attacking susceptible hosts,and shortened by 19.1%compared to that(5.20 d)in a highly resistant hosts.The results suggest that Emamectin Benzoate resistant S.exigua larvae have a negative effect on parasitoid larval development.2.Effects of pesticide resistant S.exigua on longevity and body size M.pulchricornisEmamectin Benzoate resistant(two levels)Spodoptera exigua larvae were exposed to parasitism by M.pulchricornis females,with susceptible host larvae as the controls.Longevity and hind tibia length were measured and compared between resistant and susceptible hosts.Longevity of offspring parasitoids showed a first-decreasing-then-increasing trend across increasing resistant levels of S.exigua.The longevity 8.30 d in a moderately resistant host,shortened by 22.4%compared to that in a susceptible host(10.67 d),and prolonged by 20.6%compared to that(12.93 d)in a highly resistant host.Hind tibia length of offspring parasitoids showed a linear downward trend across increasing resistant levels of S.exigua.The hind tibia length of offspring parasitoids in a moderately resistant host was 3.21 mm,shortened by 3.3%compared with the control(3.32 mm),and by 4.2%compared to that(3.18 mm)in a highly resistant host.The results suggest that Emamectin Benzoate resistant S.exigua larvae have a negative effect on offspring parasitoid development.