Effects Of Brief Exposure To High Temperature On B Iology And Antioxidative Enzymes Activity Of Athetis Lepigone

Athetis lepigone(M?schler)is a new corn insect pest in the Huang-Huai-Hai Summer Corn Region,which has four generations per year.As the major injur ious generation,the second generation causes the most damage on summer corn seedlings,and threatens the safety in production of the summer corn.As the climate warms up,the frequency of brief high temperature has been occurring more often.And the occurring period of the second generation of A.lepigone just meets the high temperature wheather.This study aims to understand the population dynamics and the therml adaption of A.lepigone during the hot summer and provide scientif ic basis for the forcasting of the insect pest based on the effects of brief exposure to high temperature in various developing stages on biology and antioxidative enzymes activity of A.lepigone.The survival rate,larval duration,pupation rate,emergence rate,pre-oviposition period,oviposition period,adult longevity,fecundity and egg hatching rate of A.lepigone reared at the constant temperature of 26?,60%±5% RH,14L:10D and treated with heat stress at 35,38,and 41? for 0.5,1,2,4,and 6 h(60%±5% RH),respectively,in different development stages of A.lepigone(1-day-old egg,2-day-old egg,4-day-old egg,1-day-old larva,6-day-old larva,12-day-old larva,18-day-old larva,1-day-old pupa,3-day-old pupa,6-day-old pupa,1-day-old female and male adult,2-day-old female and male adult)were observed and compared with the untreated control reared at the constant temperature of 26?.According to the study,some conclusions are as follows.For egg treatments,high temperature did not affect egg hatching rate,the development of pupa and adult,and the egg hatching rate of next generation.But the larval duration was prolonged with the increas e of temprature.For larval treatments,with the increase of temperature and the elapse of exposure time,the survival rate of larvae decreased and the larval duration was prolonged,but no significant differences were observed in pupa,adult,and egg hatching rate of next genaration between the heat stress groups and the control.For pupal treatments,the pupal duration was prolonged.The emergence rate decreased.The pre-oviposition period was prolonged.The oviposition period and adult longevity shortened.The female fecundity decreased.But no difference was found in egg hatching rate of the next generation.For adult treatments,there was no signif icant difference in survival rate between newly emerged adult and control.The female fecundity decreased.The adult longevity shortened.But hight temperature had no effect on egg hatching rate of next generation.The survival rate of the adults near ly to mate or to oviposit decreased with the increase of temperature and the elapse of expposure time.The pre-oviposition period was prolonged.The oviposition period and adult longevity shortened.The female fecundity decreased.But no difference was found in egg hatching rate of the next generation.In addition,the SOD,POD,CAT and T-AOC activities of A.lepigone reared at the constant temperature 26? and treated with heat stress at 35,38,and 41? for 0.5,1,2,4,and 6 h,respectively,in different stages(12-day-old larva,18-day-old larva,1-day-old pupa,3-day-old pupa,6-day-old pupa,1-day-old female and male adult,2-day-old female and male adult)were determined and compared with the untreated control reared at the constant temperature 26?.The main experimental results are as follows.For larval treatments,when the high temperature was at lower temperature,the SOD activities increased with the elapse of exposure time.But when the temperature became higher,it decreased with the elapse of exposure time.The SOD activities of older larvae were significantly higher than that of younger larvae.The POD and CAT activities of younger larvae increased with the elapse of exposure time.The POD activities of older larvae showed the trend of first increased then decresed with the exposure time lasted,and the CAT activities were higher than that of control and younger larvae.The T-AOC activities of younger larvae increased with the elapse of exposure time,but not for the older larvae.It was indicated that the younger larvae had a higher heat tolerance than that of older larvae.For pupal treatments,3-day-old showed the highest T-AOC activities,followed by 6-day-old and 1-day-old pupae.The SOD and POD activities of adults that close to mate and oviposit were higher than that of newly emerged adults,but the CAT and T-AOC showed lower activities.Besides,the SOD,POD,CAT and T-AOC activities of male were all higher than that of female.