D3263: Optimum timing for the control of fall armyworm in maize fields in Thailand

Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is a polyphagous insect that originated from the American continent. Recently, the insect invaded into Indochinese Peninsula, including Thailand. Presently, FAW has become one of the most serious pests affecting maize production in the region. In addition, development of insecticide resistance in the pest is a major concern. Population dynamics-based risk assessment is required to develop an integrated pest management system against FAW. The pheromone trap is commonly used for the estimation of insect population dynamics. However, the trap does not work well in several countries located in the Indochinese Peninsula, and the reason behind it is unclear. Therefore, we investigated the population dynamics of FAW by counting the numbers of egg mass, which are easily found in fields. A field survey was conducted in six experimental maize fields in Nakhon Sawan Province in northern Thailand. Three fields were treated with pesticides according to the recommendations of the Department of Agriculture, Thailand, and the other three fields were left untreated. After budding, the numbers of newly laid egg mass were counted every three days. The results showed that new egg masses were found in all plots almost every time until several weeks before harvest. Therefore, it is necessary to develop control measures in this region based on the assumption that FAW may continuously invade the field from the early stages of cultivation.