Using the sun at night to protect plants from defoliation by Chinese rose beetle (Coleoptera: Scarabaeidae)

 

Adult Chinese rose beetles (Adoretus sinicus Burmeister) are herbivores that feed at night on a wide range of host plants, including food crops such as cacao, persimmon, longan, eggplant, beans,  and sunflower, as well as ornamentals such as roses and hibiscus.  Aggregate feeding damage can be serious enough to cause stunting or even death of a plant.  During the day, adult beetles stay sheltered in the soil or in surface leaf litter, emerging at dusk to choose their nighttime feeding location.  It has been observed that beetles will avoid feeding on plants that are illuminated at night, such as plants positioned under street lights.  Using castor bean (Ricinus communis L.) as a test plant, we tested whether a solar powered light set-up could be used to protect plants from defoliation.  The use of a solar-based system gives flexibility for light placement without concern for proximity of electricity.  We found that a solar powered light system that switched on at dusk within 15 minutes (before or after) sunset was able to decrease beetle numbers on castor bean, with the percentage reduction in beetle numbers varying with the light intensity to which the plant had been exposed.