Evaluating repellent technologies for ambrosia beetle management in nursery production

Ambrosia beetles (Coleoptera: Scolytidae) (ABs) are small fungus-farming beetles that damage stressed ornamental nursery trees. When stressed, trees emit ethanol, which is the primary attractant for these beetles. Unfortunately, effective pesticides for managing ambrosia beetles are limited. To address the issue, we investigated the impact of previously reported repellent compounds used for different purposes. Three experiments were conducted using ethanol baited bolts to assess the efficacy of these repellents. In the first experiment, ethanol baited balsa (Ochroma pyramidale) dowel with repellents (cedarwood oil (CO2-derived), 2-butoxyethanol, 2-ethyl-1-hexanol, Beetle Guard (BG), and untreated control) were tested. The second experiment assessed the repellent efficacy of BG against ABs from ethanol infused dogwood (Cornus florida) bolts at different rates of ethanol emission (low, medium, high). In the third experiment, the impact of the distance of the repellent’s effectiveness on ethanol infused bolts and flooded Dogwood plants was studied. These experiments were conducted in the field in a randomized complete block design. Beetle Guard, an experimental repellent formulation by ISCA, seems to be an effective repellent in all three experiments. A follow up container study was conducted to mimic container nursery production systems. Our findings suggest that repellent technologies may be useful for reducing beetle attacks on stressed trees. We will discuss our results in the context of developing an effective AB management system for use in ornamental nursery production.