| Meteorus pulchricornis (Wesmael) is a solitary endoparasitoid of numerous lepidopteran pests,from the gypsy moth, Lymantria dispar (L.), to noctuid pests such as the cotton bollworm, Helicoverpaarmigera (H bner) and beet armyworm, Spodoptera exigua. It plays an important role in the IPM oflepidoptera pests. However, the extensive use of fungicides brings serious threat to the survival,development and fecundity of natural enemies.This dissertation evaluated the side effects of strobilurinand triazole fungicides that widely used on disease control on M. pulchricornis under laboratoryconditions. A comprehensive research on the two kinds fungicides provided scientific basis forbiological control. At the same time, It is beneficial to coordinate with the application of biologicalcontrol and chemical control. Results showed that trifloxystrobin showed highest effect amongstrobilurins with the estimated50%life time(LT50) of1.94days in contact treatments. The LT50forazoxystrobin,kresoxim-methyl and control was22.13,43.00and53.5days. Among the triazolefungicides, penconazole had the highest toxicity to M. Pulchricornis with the LT50of2.80days.Flutriafol showed the lowest toxicity, with the LT50was up to52.29days. In feeding treatments, theLT50of control, azoxystrobin, kresoxim-methyl, trifloxystrobin, flutriafol, myclobutanil, tebuconazole,hexaconazole,and penconazole was64.2,34.7,52.8,19.9,45.6,43.2,41.3,65.8and25.1days,respectively.Effects of fungicides on parasitism and developmental performances of M. pulchricornis werestudied systematically to investigate the sublethal effects of penconazole and trifloxystrobin onparasitoid. Both fungicides significantly reduced parasitism and rates of cocoon formation when copedwith adult wasps with field-recommended concentrations. Penconazole had significant effect onlongevity of parasitoid offspring. Some life history parameters of the parasitoid were affected byapplication of penconazole and trifloxystrobin at the egg and larval stages. The egg-to-adultdevelopment time in M. pulchricornis was significantly longer than control, adult longevity and weightwas reduced significantly. Further study indicated penconazole and trifloxystrobin showed inhibitiveactions on activity of carboxylesterase (CarE) but inductive actions on glutathione S-transferases(GSTs).In general, this study suggested that strobilurin and triazole fungicides had lowly acute toxicity onM. pulchricornis. However, they had significant effect on the longevity, growth, development, anddetoxifying enzymes of M.pulchricornis. Therefore, the impact of fungicides on natural enemies can notbe ignored, especially their sublethal effects for which more comprehensive and systematic research areneeded. |
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