短期高温对梨小食心虫成虫生殖及寿命的影响

Effects of short-term heat treatment on adult's reproduction and longevity of oriental fruit moth, Grapholita molesta Busck

【目的】研究短期高温对梨小食心虫成虫寿命和生殖的影响,可为梨小食心虫种群动态的准确预测预报提供理论依据。【方法】分别在温度(26±1)℃(、29±1)℃(、32±1)℃(、35±1)℃(、38±1)℃,相对湿度(70±10)%,光周期15L/9D,光照强度4 800 lx的人工气候箱中,对梨小食心虫初羽化成虫进行48 h处理,以(26±1)℃为对照,观察短期高温处理对梨小食心虫成虫存活的影响。随机选取经高温处理48 h后的雌虫,与在26℃下正常饲养的雄虫各10头配对,置温度26℃±1℃,湿度70%±10%,光照15L/9D,光照强度4 800 lx的人工气候箱中饲养,每天定时观察并记录成虫繁殖的影响,直至成虫死亡;随机选取经高温处理48 h后的雄虫,与在26℃下正常饲养的雌虫各10头配对,与前同法观察高温处理雄虫对梨小食心虫雌虫繁殖的影响。【结果】38℃处理对梨小食心虫有很高的致死率,处理48 h后雌虫的死亡率为91.67%,雄虫的死亡率为95%。短期高温处理雌虫对梨小食心虫产卵前期的影响不显著,但处理雄虫对梨小食心虫产卵前期有显著影响,产卵期随处理温度的升高呈缩短趋势,26℃条件下梨小食心虫雌虫的产卵期最长,为12 d;35℃处理雄虫的产卵期最短,为6.67 d;短期高温处理雌、雄虫对梨小食心虫的单雌产卵量均有显著的影响,26℃条件下,单雌产卵量为74.83粒,显著高于其他温度处理;26℃条件下梨小食心虫的卵孵化率最高,为98.89%,35℃雄虫处理的孵化率最低,为28.89%;雌雄虫的寿命均随着处理温度的升高而缩短,26℃条件下雌雄虫的寿命最长,雌虫寿命为14.64 d,雄虫寿命为14.35 d,二者均显著长于32℃和35℃处理。【结论】短期高温处理对梨小食心虫成虫的存活、繁殖与寿命均有显著的影响,其中38℃高温处理48 h,雌雄虫几乎不能存活;35℃高温处理48 h,存活率虽然受影响不大,但繁殖力急剧下降。短期高温为梨小食心虫的防治提供一条新的途径,尤其是在果树大棚内通过短期提高棚内温度来防治梨小食心虫在理论上是可行的。

【Objective】The oriental fruit moth, Grapholita molesta Busck, a major pest in orchards of China, is widely distributed nationwide except Tibet. The larva of G. molesta can bore into twigs or fruits, with the feature of generation overlapping and reproducing about 2-7 generations per year. All the features result in the difficulty in forecasting and controlling. In recent years, with the increasing of fruit production, the damage caused by G. molesta has been aggravated in many areas of our country, and has caused devastating impacts on the commercial fruit production. In this study, the influence of short-term heat treatment on the longevity and reproduction of G. molesta was studied to provide a theoretical basis for the accurate prediction of the population dynamics.【Methods】Newly emerged moths were treated at five temperatures for 48 h in climate chambers:(26±1)℃(as the control),(29±1)℃,(32± 1)℃,(35±1)℃ and (38±1)℃,with the relative humidity of (70±10)%, the light period of 15L:9D and the light intensity of 4 800 lx to observe the effect of short-term heat stress on the survival rates. Females stressed for 48 h under high temperature conditions were randomly selected and paired with 10 males in control. Then the paired moths continued to be raised at the temperature of (26±1)℃, the humidity of (70±10)%, the light period of 15L: 9D and the light intensity of 4 800 lx. The oviposition and survival rate of each pair was observed and recorded every day until death. In the same way, males stressed for 48 h under different high temperature conditions were randomly selected and paired with unstressed females. The paired moths continued to be raised at the temperature of (26±1)℃, the humidity of (70± 10)%, the light period of 15L: 9D and the light intensity of 4 800 lx. The oviposition and survival rate of each individual was also observed and recorded every day until death.【Results】There was a high mortality for adults at the treatment of 38 ℃ for 48 h. Under this condition, the mortality of females and males was 91.67% and 95%, respectively. There was a significant influence on the pre-oviposition period of females when the corresponding male suffered a short-term heat treatment, and there was a significant impact on the pre-oviposition period of females themselves that were stressed at different temperatures for 48 h. With the increasing of temperature, the oviposition period was shorter. The longest oviposition period was 12 d at 26 ℃, and the shortest oviposition period was 6.67 d for males at 35 ℃. Shortterm heat treatment had significant influence on the egg amount laid by the female. With the rising of the temperature, the egg amount laid by the single female decreased before the age of 10 d. The egg amount laid by the single female was 74.83/♀ in average under the condition of 26 ℃, which was significantly higher than other treatments. The lowest single female egg laying amount was 2.58/♀ when males suffered a short-term heat treatment at 35 ℃. At the same level of the temperature treatment, the influence of temperature on the female was significantly higher than that on the male. Short-term heat treatment had significant influence on the hatch rate of the egg. The hatch rate decreased with the rise of temperature. Under the condition of 26 ℃, the hatch rate was 98.89%, reaching the highest value. The hatch rate was 28.89% when males suffered a short- term heat treatment at 35 ℃. Except 35 ℃, the hatch rate showed no significant difference in whether males or females were treated respectvely under the same temperature stress. Oviposition peak appeared from 5 d to 14 d after eclosion. The earliest oviposition peak appeared at 7 d after eclosion at 26 ℃. With the rise of short-term temperature, the oviposition peak was delayed, and the peak of egg laying amount per day and the longevity of adults decreased. Adults had the longest longevity at 26 ℃, which reached 14.64 d for females and 14.35 d for males. Adults had the shortest longevity at 35 ℃, which reached 10.14 d for females and 9.87 d for males.【Conclusion】Short-term high temperature treatments had significant effects on the survival rate, reproduction and longevity of adults of G. molesta. Among them, the male and female hardly survived at 38 ℃ for 48 h. At 35 ℃, the survival rate was not affected, but the fecundity declined drastically. With the increase of treatment temperature, the life span was shortened, the reproductive capacity was reduced, and the amount of eggs decreased. This indicated that short-term high temperature can significantly inhibit the reproduction and lifespan of G. molesta, which provided a new way for the prevention and control of this pest. Especially in the greenhouses used for growing fruit crops, it is theoretically feasible to control G. molesta by short-term increase of the temperature in the shed.