Geographic variation of sex pheromone of oriental armyworm Mythimna separata associated with overwintering sites and migration

In China, the sex pheromone component of the oriental armyworm has always been considered to be cis-11-hexadecenal (Z11-16:Ald), but inconsistent and confused results have been found in practical use in the field trapping throughout the country. We confirmed two types of sex pheromones in the oriental armyworm by extract and analysis of pheromone gland from single female moth. The EAG results show that there are two types of male moths collected in the field. One type has strong EAG response to Z11-16:Ald but weak to Z11-16:Ac and Z11-16:OH, and the other type has strong responses to Z11-16:Ac and Z11-16:OH but weak response to Z11-16:Ald. Therefore, two types of mixtures have been evaluated in several locations from South to North China in the last several years.  One mixture is composed of key component Z11-16:Ald, and other isomers. cis 11-hexadecenol (Z11-16:OH) has been found to be an inhibitor, and hexadecanal has no synergistic effect. Another is a mixture of cis-11-hexadecenyl acetate (Z11-16:Ac) and Z11-16:OH. The most optimal ratio was found to be 8:2. It is mainly composed of Z11-16:Ac and Z11-16:OH in Guangdong. This blend was also found active in the coastal areas such as Zhejiang, Guangdong and Hainan in spring, but both blends are attractive in autumn. Basically one of the two or mixed are attractive in other locations, which depends on the locations. Therefore, it is inferred that the sex pheromone composition of the oriental armyworm is related to climatic and geographical locations, and there are differences in different years. Therefore, the monitoring of the oriental armyworm needs to be employed by two blends at the same time in China.