Seasonal fluctuation and infestation levels of Xylosandrus compactus (Coleoptera: Curculionidae) on coffee in Hawaii

The Asian black twig borer (BTB), Xylosandrus compactus (Coleoptera: Curculionidae), is among the most aggressive pests of coffee in Hawaii. This invasive weevil attacks more than 224 plant species including endemic forest trees. The control method used currently is sanitation by pruning. This tactic reduces vegetative plant material and many farmers do not use adequate methods to destroy infected branches, thus leaving an important reinfection source on the ground. Traps baited with 95 % ethanol can serve as a monitoring and research tool to assess seasonal fluctuations. Ten Japanese beetle traps were distributed randomly in eight coffee farms in Kona, Hawaii at different elevations. The traps were baited with 95 % ethanol to monitor the BTB population and checked approximately for two years. Number of BTB was quantified for each trap, infested coffee branches were collected for each farm, populations of all BTB stages were quantified, and number of infested trees was quantified for each farm. We found a seasonal effect and plant stress effect on BTB population fluctuations. BTB populations show seasonal fluctuations throughout the year; populations are higher during the dry season. BTB population levels are directly related to plant stress, including harvesting and dry season. There were significantly more BTB at lower elevations than higher elevation farms. There was a direct correlation between the infestation level and number of BTB collected in traps. Traps baited with ethanol can be an important tool for monitoring adult insect populations as part of an integrated pest management program.