我国2008年草地螟大发生特征及成因分析

为了更好地总结草地螟的发生危害规律，改善和提高草地螟的预测预报水平，本文就我国2008年草地螟的大发生危害特征及原因进行了总结分析。所得的结果表明：1代幼虫发生危害较轻，仅有70万hm2左右。但2代幼虫的危害面积则达到了1 106.7万hm2，横跨东西7个省，为历年、历代最重。在多数受害较重的地区，豆类、向日葵等双子叶作物受害最重，损失最大，而其他作物几乎都受到了危害。另外，新疆1、2代幼虫的危害时期均比内陆地区提前了1个月左右，而1代成虫的暴发也影响到了奥运会。对2代幼虫大发生的原因进行分析的结果表明，1代幼虫滞育比例的下降，1代成虫从俄罗斯亚洲部分及蒙古地区的大量迁入，1代成虫盛发期间降雨量的增加和适宜的气温，是2代幼虫大发生的主要原因。双子叶杂草面积的扩大，也为2代幼虫的大发生提供了最基本的条件。

Characteristics and causes for the outbreaks of beet webworm, Loxostege sticticalis in northern China during 2008

The beet webworm (BWW), Loxostege sticticalis L. (Lepidoptera: Pyralidae) is a serious agricultural pest of food, fiber and fodder plants in northern China. To understand the nature of population dynamics and improve the monitoring, forecasting and managing levels for this pest, characteristics and causes for the outbreaks occurring in 2008 were summarized and analyzed in this paper. The areas damaged by BWW in the first generation were around 700 thousand hectares and larval populations only sporadically occurred. The larvae in the second generation were, however, serious outbreaks. Total areas damaged were increased to 11 millions hectares, covering 7 provinces during August and early September, which is 12 times of that the first generation, and constituted the most destructive generation or year in the history. Beans, sunflowers and other dicotyledonous plants were subjected to the most damage although almost all the crops were attacked. The causes for the outbreaks were attributed to the global warming, which resulted in decrease in proportion of diapausing larvae because the raise of temperature in July. The second reason is that large adult populations invaded from the Asian parts of Russia and Mongolia from the end of July to the middle of August. Increase of deposition and humidity and suitable temperature in the outbreak areas during this period were considered as the third reason for the outbreaks since reproductive potentials of adults are greatly favored under such environmental conditions. Expanding of dicotyledonous plants in the grassland and the arable lands might also contribute to the outbreaks for these plants that are the more benefits to the larvae.