Cheng Weining, Long Zhiren, Zhang Yudong, Liang Tingting, Zhu-Salzman Keyan
Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China.
Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China.
J Insect Physiol. 2017 Nov;103:78-85. doi: 10.1016/j.jinsphys.2017.10.001. Epub 2017 Oct 4.
Sitodiplosis mosellana, one of the most important wheat pests, goes through larval diapause in a cocooned form. It is univoltine, but some individuals exhibit prolonged diapause. In this study, we documented diapause termination rate of cocooned larvae at different diapausing periods and time required for adult emergence when they were brought to 25°C from the field in northern China. We found that field larvae all entered diapause by June, but none terminated diapause until late September when the daily average temperature dropped to below 20°C. Furthermore, termination rate increased significantly as diapausing larvae underwent increasing chilling duration, reaching >95% from early December to early March. Our results suggest that chilling was necessary for diapause to terminate and that field diapause termination ended in early December. To explore low temperature and duration required, we cold-treated field diapausing larvae of different periods at different low temperatures for various lengths of time prior to the 25°C incubation. Chilling at 4-8°C for 60-90days resulted in a higher termination rate (>90%) and shorter adult emergence time in general. Additionally, we investigated the combined effect of temperature (18-30°C) and soil moisture (20-60%, on dry weight basis) as well as the effect of photoperiod (24:0-0:24L:D) on post-diapause development. While photoperiod did not affect adult emergence, soil moisture ranging from 30 to 50% and temperature from 22 to 26°C resulted in the highest adult emergence rates (>46%) within relatively short time (<18days). Mortality and/or prolonged diapause rate drastically increased when incubation conditions were outside the optimal range, especially at 30°C. These findings provide new insight into the diapause process of S. mosellana, and information will be useful for development of field forecasting and laboratory rearing techniques of this pest insect.
麦红吸浆虫是最重要的小麦害虫之一，以结茧形式经历幼虫滞育。它一年发生一代，但有些个体表现出延长滞育。在本研究中，我们记录了在中国北方田间采集的结茧幼虫在不同滞育期的滞育终止率以及将它们置于25°C时成虫羽化所需的时间。我们发现，田间幼虫在6月前全部进入滞育，但直到9月下旬日平均气温降至20°C以下时才开始有滞育终止。此外，随着滞育幼虫经历的低温持续时间增加，滞育终止率显著提高，从12月初到3月初达到>95%。我们的结果表明，低温是滞育终止所必需的，田间滞育终止于12月初结束。为了探索所需的低温和持续时间，我们在25°C孵化前，将不同时期的田间滞育幼虫在不同低温下处理不同时长。在4-8°C下冷藏60-90天通常会导致较高的终止率（>90%）和较短的成虫羽化时间。此外，我们研究了温度（18-30°C）和土壤湿度（以干重计为20-60%）的综合影响以及光周期（24:0-0:24L:D）对滞育后发育的影响。虽然光周期不影响成虫羽化，但土壤湿度在30%至50%之间以及温度在22至26°C之间会在相对较短的时间内（<18天）产生最高的成虫羽化率（>46%）。当孵化条件超出最佳范围时，尤其是在30°C时，死亡率和/或延长滞育率会急剧增加。这些发现为麦红吸浆虫的滞育过程提供了新的见解，这些信息将有助于开发这种害虫的田间预测和实验室饲养技术。
