Phenology and Monitoring of the Lesser Chestnut Weevil (Curculio sayi)

Abstract

With the introduction in recent years of high-yield blight-resistant chestnut varieties, the commercial chestnut industry in the United States is expanding. Accompanying this expansion is a resurgence in a primary pest of chestnut: C. sayi, the lesser chestnut weevil. This weevil damages the nut crop and infestations can surge from 0 to close to 100% in as little as two years. Understanding the dynamics of this pest has been challenging. Most work was conducted in the 1900s and only recently has this weevil garnered renewed interest. Recent work on C. sayi phenology has been completed in Missouri but conflicted with anecdotal reports from northern growers. From 2019 to 2020, we used a combination of trapping and microcosm studies to understand both C. sayi phenology and the means of monitoring this pest. C. sayi populations were univoltine and peaked in mid-October. Pyramid traps were the most effective at capturing adult C. sayi. C. sayi larvae, pupae, eclosed adults, and emerging adults were recovered from microcosm experiments. These results suggest that C. sayi emerges later in the northern US with the potential for a single generation to emerge over multiple subsequent years. Understanding C. sayi phenology along with the means of monitoring forms the basis for effective management and control in commercial chestnut orchards.