Joshi Ankush, Olson Denise L, Carey Donald R
Entomology Department, Hulz Hall, North Dakota State University, Fargo, ND 58105, USA.
Environ Entomol. 2009 Dec;38(6):1539-45. doi: 10.1603/022.038.0604.
We evaluated the effects of snow cover and debris cover on overwintering success of Aphthona from 2001 to 2004 in southeast North Dakota. Chill degree-days, soil temperature, and duration of soil temperatures were monitored in field plots. Emergence of Aphthona from soil cores collected in October and held in the laboratory under simulated winter conditions did not differ across treatments. Field emergence of Aphthona was significantly reduced compared with emergence of Aphthona in the laboratory under simulated winter. Snow cover protected overwintering of Aphthona during 3 yr. Overwintering success was 77-94% lower in no-snow plots than in snow plots except in 2002. In 2001, when the soil temperature was as low as -4.4 degrees C, 90% of the Aphthona beetles emerged from snow-covered plots. The ranges of winter temperature and winter period for overwintering Aphthona were determined as -5.0-4.5 degrees C and 56-132 d, respectively, by using linear regression. A negative linear relationship between soil temperature and winter period may help predict the minimum needed overwintering period at a given winter temperature. Warmer temperatures during the winter of 2002 caused snow to melt in the snow plots, which led to excessive moisture that seemed to reduce overwintering success of Aphthona in those plots. Overall emergence was too low to conduct statistical procedures in 2003 and 2004 because of temperature extremes and warm periods during the winters that may have caused Aphthona to break diapause prematurely.
2001年至2004年期间，我们在北达科他州东南部评估了积雪和残枝覆盖对萤叶甲越冬成功率的影响。在田间地块监测了冷温积日、土壤温度和土壤温度持续时间。10月采集并在实验室模拟冬季条件下保存的土壤芯中萤叶甲的出土情况在各处理间无差异。与实验室模拟冬季条件下萤叶甲的出土情况相比，田间萤叶甲的出土显著减少。积雪在3年中保护了萤叶甲越冬。除2002年外，无雪地块的越冬成功率比有雪地块低77% - 94%。2001年，当土壤温度低至 - 4.4℃时，90%的萤叶甲从积雪覆盖的地块中出土。通过线性回归确定，萤叶甲越冬的冬季温度范围和冬季时长分别为 - 5.0 - 4.5℃和56 - 132天。土壤温度与冬季时长之间的负线性关系可能有助于预测在给定冬季温度下所需的最短越冬时长。2002年冬季气温较高，导致有雪地块的雪融化，进而导致水分过多，这似乎降低了这些地块中萤叶甲的越冬成功率。由于2003年和2004年冬季的极端温度和温暖期可能导致萤叶甲过早打破滞育，总体出土率过低，无法进行统计分析。
