Dr. Jason Oliver at the TSU Otis Floyd Nursery Research Center in McMinnville alerted us that they had caught a single granulate ambrosia beetle adult and two black stem borers in their ethyl alcohol baited trap when it was checked on Wednesday, March 18.
As spring approaches, so too do the emergence of these pests as temperatures at or above 70 degrees F are conducive for ambrosia beetle activity. They primarily attack trees that are stressed and dormant, which many plants, especially if they were not irrigated last August through October could have been damaged by the flash drought. Often, these plants will not show signs of stress because of their dormancy.
The granulate ambrosia beetle is an invasive pest from Asia that has been in the country since 1976. It tends to attack trees when they are stressed and releasing ethyl alcohol. The adult beetles chews through the bark and into the wood for a half-inch or more. It makes a nice clean gallery (tunnel) and inoculates the gallery with white ambrosial fungi. The adult female lays her eggs along the side of the gallery and when they hatch, the larvae feed on the ambrosial fungi. The round holes in the tree are about 1 mm in diameter. When the beetle is chewing its way into the tree, fine boring sawdust-like frass (insect excrement) is exuded out of the holes. These filaments can be seen sticking out of the trunk or branches of the tree. The holes in the tree are an entryway for other more pathogenic fungi such as Fusarium spp. which infects the vascular system of the tree and causes dieback of branches and even death of the whole plant within weeks.