Shallot (Allium ascalonicum L.) is one of the horticultural commodities that have high economic value in Indonesia. The caterpillar, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), is an important pest of shallot crops which decreases both production and yield quality. Farmers commonly spray pesticides to control S. exigua. This can cause negative impacts on the environment and farmers’ health. Therefore, environmentally friendly control measures need to be implemented. Use of sex pheromone traps can be an alternative in controlling S. exigua. This research aims to study the effect of moonlight and rainfall on the number of male imagos of S. exigua captured in sex pheromone traps and to study the correlation of the number of S. exigua imagos captured on the percentage of infested leaves and shallot yield. This study was conducted from March to June 2016 in Labuhan Lombok Village, East Lombok Regency, West Nusa Tenggara (NTB) Province, Indonesia. Sex pheromone traps were randomly set on 12 shallot cultivation plots (Super Phillips variety). The number of male moths caught was recorded every 3-4 days, and then at the end of observations the percentage of infested leaves was determined. The number of captured male imagos of S. exigua had a significant linear relationship with the percentage of infested leaves and shallot yield with the correlation coefficient values of -0.607 and 0.829 respectively. The application of sex pheromone traps to control S. exigua on shallot, during moonlight and rainfall, has the potential to decrease both insecticide and production cost and to increase farmers’ income.