Annual Migration of Cabbage Moth, Mamestra brassicae L. (Lepidoptera: Noctuidae), over the Sea in Northern China

The cabbage moth, Mamestra brassicae L. (Lepidoptera: Noctuidae), is a serious pest of vegetable crops throughout the world. In order to determine whether or not M. brassicae is a migrant, and if yes, what is the pattern of M. brassicae seasonal migration, a long-term study on M. brassicae from April to October in 2003-2014 was carried out by means of a searchlight trap on a small island located in the center of the Bohai Strait. The results show that a large number of M. brassicae were trapped every year on the island, which indicates that M. brassicae is a migrant and migrated at least 40-60 km across the Bohai Strait. The mean migration period of M. brassicae over the sea within one year is 151 ± 8 d in 2003-2014, with the shortest time span 78 d in 2003 and the longest 189 d in 2014, respectively. The number of M. brassicae captured, however, varies considerably between months or years. The majority of captures were female, with different levels of ovarian development and mating status. Most of the females trapped in May-July during 2010-2014 had a high mating rate and advanced level of ovarian development, suggesting that the migration of this species does not conform to the hypothesis of 'oogenesis-flight syndrome'. The findings of the present study are beneficial to the development of forecasting systems and management strategies of M. brassicae.