Early Detection of Ambrosia Beetles Saves Thousands for Local Nursery

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Granulate [Asian] ambrosia beetles are destructive insect pests, and a big concern for nursery growers throughout North Carolina. These tiny insects are attracted mainly to stressed or recently-transplanted trees, as well as trees with thin bark (i.e. maple species) that are roughly 1-2 inches in diameter. Once the beetles are inside the trees no insecticides are effective and the only control measure available is to destroy the infested crop.

Granulate ambrosia beetles are highly destructive pests in nursery crops. Photo credit: JR Baker, NCSU

Maple trees are a popular and high value crop for many nursery growers throughout NC and one of the main crops for a local nursery grower that visited our office in 2020 with visible signs of infestation in their maple trees. Unfortunately they had to destroy nearly 50% of the plants, which resulted in thousands of dollars of lost revenue for that particular crop for the 2020 growing season.

In spring of 2021, the Haywood County Horticulture Agent set up a monitoring/trapping system with the nursery manager to detect early emergence of granulate ambrosia beetles. Traps were checked on a weekly basis and the agent showed the nursery manager what to look for, how to reset traps, and subsequent thresholds that would determine when a spray program should begin.

Pitch tubes created by tunneling activity of granulate ambrosia beetles. Photo credit: gardeningknowhow.com

As a result of early detection trapping, GAB emergence and relative numbers were accurately detected and a treatment threshold established. Once numbers of GAB reached the economic threshold (ET), weekly spray treatments began. To date, no trees have been negatively impacted by GAB, resulting in $4,500 in savings to the grower. Not only were the trees themselves saved, but this has also opened the door for greater interaction between the Horticulture agent and the Nursery manager. So far in 2021, we have been able to work on 3 major projects that will continue to improve plant production and the relationship with Cooperative Extension and a major producer in Haywood County.

Home gardeners can use this trapping method for trees in home landscapes as well. Find more on granulate ambrosia beetles and how to construct traps here.

Traps are a low cost, easy-to-construct, and highly effective way to detect granulate ambrosia beetles. Photo credit: Sam Marshall