Use of solar-powered nighttime illumination to reduce defoliation by Chinese rose beetle (Adoretus sinicus Burmeister) (Coleoptera: Scarabaeidae) in cacao

Adult Chinese rose beetles (Adoretus sinicus Burmeister) (Coleoptera: Scarabaeidae) are polyphagous herbivores whose night-feeding can cause serious defoliation on a wide range of host plants, leading to stunting or even death of plants. Chinese rose beetles have a geographic range that includes China, Taiwan, Indonesia, Cambodia, Laos, Singapore, Thailand, Vietnam, the Marianas Islands, the Caroline Islands and the Hawaiian Islands. Chinese rose beetles are one of the most serious pests of young cacao (Theobroma cacao L.) trees and have been a problem for orchard establishment in the developing cacao industry in Hawaii. One promising pesticide-free control method takes advantage of the avoidance of light by adult beetles when they select the plant on which they will feed at night. We tested the effectiveness of nighttime illumination, provided by a portable solar-based spotlight system, as a means of reducing beetle populations in young cacao orchards. A dusk sensor activates the light system near sunset, before the onset of evening colonization of host plants by adult beetles. An integrated timer switches off the light after two hours. This system successfully protected a small cacao orchard from excessive defoliation, thereby facilitating orchard establishment. The results clearly show that nighttime illumination can be used as a means of reducing Chinese rose beetle population size, and presumed aggregate defoliation, on a host plant.