| The rice leaf folder Cnaphalocrocis medlinalis Güenée(RLF)is the important migratory pest in our country.The high temperature has significant influence on populations.The fertility decreased when the adult RLFs exposed to high temperatures;the survival rate of larval RLFs decreased significantly after heat shock and the eggs were getting dry and can't hatch under the condition of high temperature.However,there were little studies on the effect of the high temperature on RLF during pupae stage.Therefore,this paper established a method of rearing the RLFs using wheat seedlings,and measured the biological traits of RLFs exposed to high temperatures(37,39 and 41?)at the 1st to 5th-day-old pupae.The heat tolerance of RLFs to high temperature after acclimation for continuous generations at the 3rd larvae was measured.Additionally,the biological traits of the RLF after the termination of the heat acclimation were studied.The main results were listed as followings:(1)Establishment of the rearing method for RLF using wheat seedlings.The rearing method of the RLF using wheat seedlings was established,and the RLFs were conditionally reared about 36 generations in laboratory.The biological traits,such as the survival rate,developmental duration,sex ratio,eggs per female,and the hatchability of RLFs reared for 6 generations on wheat seedlings had no significant differences as insects reared on maize seedlings.Larvae RLFs rearing on wheat seedlings could use the rice seedlings well.The rearing method of RLFs using wheat seedlings was more economic and convenient than the method using maize seedlings.(2)Effect of the high temperature on the pupae.The developmental duration:the developmental duration of the RLF 1st to 5th day-old pupae was not affected by the exposure to 37?,but duration of the 1st day-old pupae significant decreased after exposing to 5h or 7h per day for 3 days.The durations of the 1st to 5th day-old pupae were prolonged with the increase of the exposure time to 39? and 41?,and the 1st day-old pupae were significantly prolonged after 1h and 3h per day under the high temperature of 39? and 41? for 2 and 3 days,but the pupa duration exposed to 39? and 41? for 5h and 7hwere not significantly different from control or even shorter than control.The eclosion rate:the eclosion rate of the 1st to 5th day-old pupae exposed to 37?for 1h,3h,5h,7h and the female pupae to 39? for 1h,3h,5h,7h had no significant differences with the control group,but the eclosion rate of the 3rd and 5th day-old male pupae were decreased significantly with the increase of the hours of heat shock,and the eclosion rate of the 1st day-old pupae decreased significantly with the increase of the exposure days under high temperature for 1 to 3 days.The eclosion rate of the 1st to 5th day-old pupae after exposing to 41? decreased with the increase of the hours of heat shock in one day.The eclosion rate of the 1st day-old pupae significantly decreased with the increase of the days of the heat shock while exposed to 41? for 1 to 7h per day for 3 days.But the eclosion rate of the RLF was close to zero after exposing to 7h per day for 3 days.The fecundity:the fecundity was significantly suppressed after the 1st,2nd,4th and 5th day-old pupae of RLF exposed to 37? for 7h and the 3rd day-old pupae exposed for 5h,but it had no significant differences with the control group after other hours in 37?.The fertility significantly restrained after the 1st day-old pupae exposed to 39? for 1 h,the 2nd and 3rd day-old pupae exposed for 3h,the 4th day-old pupae exposed for 5h,the 5th day-old pupae exposed for 7h,and it had no significant difference with the control group after other hours at 39?.The eggs per female were significantly decreased after the 1st and 2nd day-old pupae exposed to 41? for more than 1h and the 3rd day-old pupae exposed for 7h,the 4th day-old pupae exposed for 3h,the 5th day-old pupae exposed for 5h.The adults almost could not oviposit after the 1st day-old pupae exposing to 41? for 5h per day for 2 and 3 days.The fecundity of the RLF adults decreased significantly with the increase of the hours and the days of heat shock on the 1st day-old pupae at 37? to 41?.The hatch rate:the hatch rate was significantly decreased after the 1st and 4th day-old pupae of RLF exposed to 37? for 3h,the 2nd,3rd and5th day-old pupae exposed for 1h,but it was significantly decreased after the 1st to 5th day old pupae exposed to 39?and 41? for 1h and it significantly decreased with the increase of the hours and days of exposure.(3)Effect of the high temperature hardening on the larvae.The survival rate of larvae significantly decreased during the 1st to 7th generation after exposing to 41? at the 3rd-instar larvae for three days 3h per day in every generation,but it significantly increased during the 1st to 4th generations,and it significantly decreased to the levels of the 1st to 2nd generation during the 5th to 7th generation.The pupation rate was significantly lower than the control group but had no significant difference during seven generations after exposing to 41? at the 3rd-instar larvae.The duration of pupae decreased with the increase of the generations after exposing to 41? at the 3rd-instar larvae,and the duration of pupae in the 1st to 3rd generation was significantly longer than the control group,but there were no significant differences during the 4th to 5th generations,and it was significantly shorter during the 6th to 7th generations.The fecundity was significantly suppressed with the increase of the generations after exposing to 41? at the 3rd-instar larvae,and it was significantly decreased during the 2nd to 7th generations.However,the hatch rate of eggs had no significant differences during every generation,but it was significantly lower than the control group.(4)Effect of high temperature on the heat tolerance of pupae.The duration of pupae was shorten with the increase of the generations of heat exposure to 41? for 1h,3h,5h,7h at the 3rd-instar larvae for three days 3h per day during seven generations,and it became stable but still was significant shorter than the control group after heat exposure to 41? for 5 generations.The fecundity after the pupae exposing to the heat shock significantly decreased with the increase of the generations after exposing to 41? at the 3rd-instar larvae.The heat resistance to high temperature range extended but the fertility decreased after the larvae were exposed to the high temperature.(5)The ability of RLF to recovery after heat shock.The survival rate,pupation rate,pupae duration,pupae weight,the fecundity and the hatch rate of the 3rd-instar larvae at 27? for 2 generations after seven generations of exposing to 41? were significantly increased and had no significant difference with the control group,but the eggs per female were also significantly decreased in the 1st generation reared at 27?.The ability of RLFs to recovery was strong after heat shock. |
PDF Full Text Request