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

白菜环虫Trichoplusia ni（鳞翅目，夜蛾科）是美国长期以来臭名昭著的农作物害虫。然而，在日本没有关于T.ni作为农作物害虫的报道。但2000年日本西部（鹿儿岛和兵库县）白菜田出现了大量的夜蛾幼虫。大白菜环虫的分布正由日本西南部向东北部扩散。如千叶县未见幼虫，该项目于2003年首次发现T.ni。采用信息素诱捕成虫和田间采集幼虫两种方法监测白菜田稻蠹虫的年发生情况。从春季到秋季，夜蛾幼虫数量呈递增趋势。兵库县白菜田春季优势种为黑签菜，秋季优势种为毛签菜。但黑斑夜蛾幼虫的抗寒性强于黑斑夜蛾。因此，白菜田的优势种在春季再次转变为黑穗草。日语t.i的起源在这个项目中无法澄清。但佛罗里达Copidosoma对日本恙虫病的寄生率低于美国恙虫病。这些数据表明，日本白菜与美国品种有很大的不同。

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.