Ethanol release patterns and captures of Xylosandrus spp. (Coleoptera: Curculionidae) in ornamental nursery

Xylosandrus crassiusculus Motschulsky and Xylosandrus germanus Blandford are serious ambrosia beetle pests in ornamental nurseries. Three ethanol baits, AgBio low release (LR), AgBio high release (HR), and Trécé are commercially available for use in bottle traps to determine flight activity of adult Xylosandrus spp. However, release patterns of ethanol from these baits under varying temperatures and captures of Xylosandrus spp. are poorly understood. Thus, the objectives of this study were (i) to determine ethanol release rates from these baits under constant and variable temperatures and (ii) to compare relative adult Xylosandrus spp. captures using these baits in ornamental nurseries. When 3-d difference (3-d difference) bait weights were recorded under constant 15.6, 21.1, 26.7, and 32.2 °C, an increase in release rates was recorded with an increase in temperature from 15.6 to 32.2 °C for LR bait. At 32.2 °C, no increase or reduction in the 3-d-difference weights was found for the HR and Trécé baits, respectively, compared to LR bait. The 3-d-difference weights were steady with all 3 baits when temperatures gradually increased and decreased in variable sequence for 30 d. In 2022, 2023, and 2024, although all 3 baits captured adult X. crassiusculus and X. germanus, LR bait captured significantly more numbers of X. crassiusculus than the other 2 baits in 2022 and 2023, and in 2024, X. crassiusculus captures were greater in traps with the Trécé bait than the other 2 baits. Thus, ethanol baits can effectively detect the early flight activity of Xylosandrus spp. adults in ornamental nurseries.