Optimizing trap design, lure, and color for monitoring Chrysobothris mali (Coleoptera: Buprestidae) in California walnut orchards.

Abstract

Pacific flatheaded borer, Chrysobothris mali (Coleoptera: Buprestidae), is a reemerging pest of walnuts in California. With the expansion of walnut production acres and increased incidences of severe droughts that stress orchards, C. mali has gained economically important pest status in recent years. In this article, we explored different trap designs, colors, and lures for early detection and monitoring of C. mali in commercial walnut orchards in California. In multi-year studies, ground-installed 4-foot-tall purple triangular traps with adhesives on the outer surface were more attractive than the purple panel sticky traps with or without volatile lures. Furthermore, among multiple colors of triangular traps, yellow and red traps captured more C. mali adults compared to other colors, including purple, in replicated trials conducted in 2 walnut orchards. The yellow triangular trap captured adults in these walnut orchards most consistently and earlier in the season. The utility of these traps in monitoring C. mali in walnut orchards and future directions of monitoring research are discussed.