Abstract: In order to explore the occurrence characteristics and seasonal population variation of beet armyworm in suburb vegetable bases in Linhai city， population dynamics of beet armyworm was systematic monitoring using sex pheromone traps during 2002—2012. The results showed the trend of the beet armyworm population variations was in spiral wave curve from high to low， and annual outbreaking frequency was 455%. Seasonal population varied in a Wshape curve in general. First moth occurred in different years， from early April to early June. An early summer peak may appeared in early May， while a late autumn peak may appeared in early November in some years. The biggest population appeared arranging from early July to late August. The last moth appeared on early December generally. Amountclimate model indicated first moth appeared when average tenday temperature between 12-14℃， and above 18℃ the amount increased as the average tenday temperature increased till 30-32℃.This research could help to make better forecast and control decision for beet armyworm．

Key words: suburban vegetable, beet Armyworm, dynamic rule, seasonal population, temperature factor