Problematic migration to cultivated field of cabbage looper Trichoplusia ni as a pest ; Their ecological aspects and how they control.

甘蓝夜蛾Trichoplusia ni（鳞翅目，夜蛾科）是美国著名的农作物害虫。T.ni 2000年在日本西部地区（鹿儿岛县和兵库县）白菜田发现了大量的卷叶螟幼虫T.ni卷叶螟在日本的分布正从西南部向东北部扩散。例如，千叶县没有发现幼虫，而2003年本项目证实了T.ni T.ni的首次出现。从春季到秋季，T.ni的幼虫数量不断增加。兵库县甘蓝田春季优势种为黑纹银纹夜蛾，秋季优势种为粉纹夜蛾。但黑星天牛幼虫的抗寒性强于刺蛾幼虫。因此，春季甘蓝地的优势种又重新变为黑星菊。T.ni但在日本T.ni上的寄生率比美国的低。这些数据表明，日本卷叶螟与美国卷叶螟有很大的不同。

The cabbage looper Trichoplusia ni (Lepidoptera, Noctuidae) is notorious crop pest in the USA for long time. However, there was no report about T.ni as a crop pest in Japan.But there were many larvae of T.ni in cabbage field of west parts of Japan (Kagoshima and Hyogo prefectures) in 2000.Distribution of Japanese cabbage looper is spreading from south-western to north-eastern parts of Japan. For example, there was no larvae in Chiba prefecture, and first appearance of T.ni was confirmed by this project in 2003.Annual occurrence of T.ni in cabbage field was monitored by adults captured by pheromone trap and larvae by field collecting. The number of larvae of T.ni is increasing from spring to fall. The dominant species of cabbage fields in Hyogo prefecture is Autographa nigrisigna in spring, then changing to Trichoplusia ni in fall. But cold resistance of larva of A.nigrisigna is stronger than T.ni. So, the dominant species of cabbage field changing to A.nigrisigna in spring again.Origin of Japanese T.ni could not clarify in this project. But parasitism rate of Copidosoma floridamum on Japanese T.ni is lower than T.ni of the USA. These data suggested that Japanese cabbage looper is quite different from American strain.