Invasive Shot Hole Borer

The characteristics of ISHB attack and fungus infection differ among tree species. The beetle commonly attacks the main stem and larger branches of trees and shrubs, but injury can be found on twigs as small as 1 inch in diameter. The beetle produces a very precise, perfectly round, tiny (< 0.1 inches in diameter) entry hole in most trees. Wet staining and discoloration on the bark of the main stem and branches are early symptoms of beetle attack. Depending on the tree species attacked, ISHB injury can be identified either by staining, gumming, or a sugaring response on the outer bark. Infection with the fungus can cause leaf discoloration and wilting, dieback of entire branches, and tree mortality.

TREE-äge® provides 2 years of control of the beetle, while the addition of Propizol® will protect trees from the fungi introduced by the ambrosia beetle. Use a soil surfactant, such as NutriRoot®, as a sub-surface injection or drench, in combination with watering to encourage root growth, increase penetration of water into the soil, and to assure better translocation of the formulations throughout the tree.

The most significant damage occurs from May through October so if ISHB is found near or on trees under your care, treatments should be made immediately.

Generally, the best seasons for injection are spring and fall, since the best uptake occurs when trees are actively transpiring, but treatments can be made at any time of the year when there is good soil moisture to encourage translocation of the systemic formulations.

Trunk injections with insecticide or combined with fungicide will be distributed upward in the tree within 4-6 weeks with adequate soil moisture. For trees in natural, non-irrigated areas with questionable soil moisture, consider using NutriRoot to enable trees to extract water from the soil, reducing the need for watering, and resulting in faster and better movement of systemic products even in drought conditions.