The sugar maple borer is a native pest of living sugar maple trees in the United States. It is found throughout the geographic range of its host, the sugar maple. It is typically not a tree killer, but rather weakens them through their activity which may encourage secondary invaders including pests and pathogens. Adult sugar maple borers emerge in the late spring, and are seen around their sugar maple hosts for much of the summer. Adult beetles are brightly colored with yellow stripes alternating with black, yellow legs, and black antennae. The adult sugar maple borer beetles look very similar in color (but with different patterns) to the adults of the locust borer (Megacyllene robiniae) and the painted hickory borer (Megacyllene caryae). Egg laying begins in late July and early August, particularly in pockets of rough bark on the host. The adult female longhorned beetle will cut a slit in the host plant bark where she will lay a single egg. This activity is similar to what is seen with the non-native insect, the Asian longhorned beetle (Anoplophora glabripennis). Once the egg hatches, the larva bores beneath the host plant bark, into the phloem. It is common for sap to leak out of the egg laying site as a result of this activity for a time. In the first year, larvae make horizontal galleries in the interface between the sapwood and the phloem. Upon maturity, the larva tunnels inward and upward into the heartwood, where pupation occurs at the end of the gallery during the second spring. Fully grown larvae are 1.6 to 2 inches long. The life cycle of the sugar maple borer takes 2 years to complete (Johnson and Lyon, 1991).
Old trees, especially along roadside locations, are often noticeably damaged by the sugar maple borer. Open grown trees ranging from 4 to 10.5 inches in diameter at breast height are often selected first by females for egg laying. Active borer damage may be easily missed. Following adult beetle emergence, it may take several years for the tree bark to slough off. Once this happens, the old larval feeding gallery in the sapwood may be exposed. Cat-face type scars (c-shaped over 1/3 of the trunk diameter) can be found as a result of sugar maple borer feeding. After several years of feeding by this insect, infested trees may lose vigor, have smaller leaves that drop early, or have discolored canopies. Feeding is typically done in the tree's main stem (trunk). It is possible on faster growing trees that the wound is grown over. Research has shown that severe early and late season defoliation of sugar maple (from other pests such as forest tent caterpillar or saddled prominent outbreaks) may make them more susceptible/attractive for sugar maple borer attack (Wink and Allen, 2003). In fact, sugar maple borer activity may begin 3-4 years following the defoliation events, with peak activity occurring 6-8 years following. This lag may be, in part, explained by the sugar maple borer's 2-year life cycle (Wink and Allen, 2003).
Trees are rarely killed by this insect, so chemical management may be unnecessary in managed ornamental landscapes. However, the sugar maple borer is capable of severely degrading lumber quality or use.
Visually monitor for sugar maple borer adults in the spring and summer, particularly in July and August when egg laying occurs. Weeping sap from a slit in the bark of the host plant may indicate an area where an egg has been laid, however other insect activity or damage to sugar maple can look similar.
Stressed or slower growing trees are often more susceptible to sugar maple borer activity. As such, proper planting techniques on the right site, proper maintenance, and efforts to reduce host plant stress can help prevent damage from the sugar maple borer. Because the damage happens to the trunk of the tree, pruning out infested branches (for example) is not an option with this insect.
Woodpeckers are known to be predators of various life stages of the sugar maple borer, and may cause at least 46% mortality of a population. Dolichomitus irritator, a generalist ichneumonid parasitoid, was recorded from a dead sugar maple borer larva. Parasitoids are not considered to be important in regulating sugar maple borer populations due to the insect's cryptic behaviors, prolonged life cycle, and low numbers in any one host (Adams, 2017). Natural microbial infections may kill some life stages of the sugar maple borer.
Acetamiprid (L)
Azadirachtin (NL)
Beauveria bassiana (NL)
Cyantraniliprole (NL)
Emamectin benzoate (L)
Flonicamid+cyclaniliprole (N)
Imidacloprid (L)
Isaria (paecilomyces) fumosoroseus (NL)
Neem oil (NL)
Permethrin (L)
Spinosad (NL)
Tau-fluvalinate (NL)
Zeta-cypermethrin (L)
Management of the adults early (prior to egg laying) if chemical management is deemed necessary. Thorough wetting of bark especially near rough bark and wounds.
Active ingredients that may be applied systemically include: azadirachtin (injection, soil drench), cyantraniliprole (soil drench, soil injection), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (soil drench).
Isaria (paecilomyces) fumosoroseus is labeled for use as a soil application.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
