小菜蛾在温带地区越冬研究进展

小菜蛾是世界性重要害虫。在热带和亚热带地区冬季的十字花科植物上能正常发育繁殖,可见到各种虫态。但在温带冬季十字花科植物不能生长的地区,小菜蛾的越冬成为一个重要生态学问题。综述了亚洲、北美洲和欧洲小菜蛾越冬的研究进展。小菜蛾在日本的北海道、本州岛的北陆和东北大部分地区不能越冬,越冬北限相当于冬季积雪覆盖时间为60d的区域;在中国,小菜蛾不能在寒冷的东北地区越冬,在长江中下游以南地区冬季可见各虫态,但越冬北限尚不清楚;小菜蛾在冬天气候温和的韩国以及澳大利亚东南部继续发生;北美洲的加拿大西部和安大略地区大量的试验证明小菜蛾不能成功越冬,在美国南部小菜蛾冬季可正常发生,北部小菜蛾的越冬尚未见系统研究报道,但确认春季从南部运输的受小菜蛾感染的甘蓝等种苗是美国北部的重要虫源。小菜蛾在欧洲各地越冬的系统研究未见报道,没有证据表明在英国小菜蛾会发生有显著意义的越冬。目前小菜蛾越冬研究主要采用冬季直接试验观察和基于耐寒性试验的越冬预测两种方法。冬季直接试验观察法包括:(1)利用人工饲养的小菜蛾在田间各种潜在的越冬场所的越冬试验;(2)在秋播、野生或残留的十字花科植物上进行冬季种群的系统抽样调查;(3)越冬前后在前茬为十字花科植物的田块广泛搜寻普查小菜蛾的存活个体。基于耐寒性试验的越冬预测法:在获取小菜蛾越冬场所温度的基础上设计低温处理模式,试验低温处理后小菜蛾的存活率及后续发育和生殖。将试验数据和各地气温或小气候相结合,对小菜蛾在的越冬可能性进行推断。

Overwintering of the diamondback moth, Plutella xylostella in temperate countries

The diamondback moth (DBM), Plutella xylostella, is one of important horticultural pests worldwide. In the tropics and sub-tropics where crucifers are planted throughout the year all life stages of DBM appears at any time. However, in temperate regions, where crucifers are not grown year-round, hibernation of DBM becomes a significant ecological issue during noncropping periods. Research progress on hibernation of the DBM in Asian, North American and European countries are reviewed in this article. The detailed original research approaches and important experiment data were demonstrated In Japan, detailed experiments showed that DBM cannot overwinter in Hokaido and a large part of Tohoku and Hokuriku districts of Honshu. The north limit of hibernation of DBM was supposed where the duration of continuous snow cover is longer than 60 days. In China, there is evidence showing that DBM cannot overwinter in chilly North East China, but it feeds and reproduces normally during winter on south China. However, the north limit of hibernation in China remains unknown. Researchers found that DBM occurs normally during mild winter in South Korea and south-east of Australia. In North America, the detailed experiment results provided evidence that DBM cannot overwinter in Ontario and West Canada. DBM was found to feed and reproduce normally in south United States. Whether DBM hibernates in north United States remains a controversial topic. Seedlings grown in the southern states contaminated with DBM had been proven to be one of the major sources of diamondback moth infestations in northern states. In European countries, it is not known whether DBM can survive in winters in situ. The experiments have consistently shown very little survival in the U.K., and give no reason to suppose that overwintering occurs at any significant degree. There are two approaches to explore the overwintering of DBM, i.e. direct approach via field experiments and indirect approach via forecasting based on cold tolerance experiments and environment temperature. The common methods of the direct approach include field cage experiments with all life stages of DBM under the snow cover, plant debris, volunteer plants, soil gaps; field investigations for temporal dynamic of all life stages of DBM in winter crops, and field survey for natural hibernation populations of DBM on cruciferous crops before and after winter. The indirect approach is to deduce whether DBM can overwinter or not based on the results of the cold hardness tests and temperatures in the hibernation environment. World winter temperature has increased due to climate change and global warming, which has brought significant impact on the hibernation of DBM. It should be further studied the north limit of hibernation associated with the migration of DBM in temperate countries to provide evidence for the forecast and management of DBM.