Control of Chinese rose beetle through the use of solar-powered nighttime illumination

Chinese rose beetle, Adoretus sinicus (Burmeister) (Coleoptera: Scarabaeidae: Adoretini), found in Asia and the Pacific Islands, was first reported in Hawaii (USA) in 1891. Adults feed at night on leaves of a wide range of plant species. Aggregate feeding can stunt or even kill host plants. Chinese rose beetle is one of the most serious pests of young cacao [Theobroma cacao L. (Malvaceae)] trees, and has 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 light-emitting diode spotlight system as a means of reducing beetle populations on host plants, first using castor bean, Ricinus communis L. (Euphorbiaceae), as a test plant, followed by orchard-scale testing in young cacao orchards. Using Chinese rose beetle-populated castor bean plants, counts were made of numbers of beetles on both non-illuminated and illuminated plants. Nighttime illumination suppressed beetle numbers, with increased suppression associated with extended duration of illumination (number of nights) and with increased intensity of illumination: 2.5 lux was sufficient to give >50% suppression, and 4.0 lux was sufficient to give >75% suppression over 4 nights of illumination. In cacao orchard tests, there was over 93% reduction of beetle numbers in each test orchard, following 4 nights of illumination. 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. We believe that this is the first report of the use of nighttime illumination as a means of suppressing damage of plants by insects.