The Asian Longhorned Beetle (ALB), an invasive wood-boring insect, poses a significant threat to North American hardwood trees. It feeds on a broad range of host species, primarily targeting deciduous trees in urban and forest ecosystems. Understanding the beetle’s diet is crucial for implementing quarantine measures and protecting vulnerable tree populations from infestation.
Primary Host Trees
The Asian Longhorned Beetle primarily prefers trees in the Acer genus, making maples its most commonly infested host in North America. Highly susceptible species include Norway maple, sugar maple, and red maple. This preference is likely due to chemical attractants and the wood’s suitability for larval development.
Infestation in these primary hosts is typically fatal because the beetle successfully completes its life cycle within the tree’s structure. Besides maple, other trees considered very good hosts include willows, elms, birches, and horse chestnuts. Larvae thrive in these species, leading to repeated attacks that ultimately girdle the tree and cause death.
Secondary and Occasional Host Trees
When primary hosts are scarce or populations are high, the ALB attacks a wider variety of secondary and occasional host trees. These species are vulnerable, but they may not support the beetle’s full developmental cycle as efficiently as preferred hosts. Examples include ash, poplar, London plane, mimosa, and hackberry.
The beetle has been documented attacking dozens of tree species from over 15 plant families, including sycamore, goldenraintree, and mountain ash. Although the success rate of larval development can be lower in these occasional hosts compared to maples and elms, any infestation requires immediate action to prevent the beetle’s spread.
How Feeding Differs Between Life Stages
The feeding habits of the Asian Longhorned Beetle vary between the adult and larval life stages, with larvae causing most of the destructive damage. Larval feeding begins shortly after hatching, as the young insect consumes the phloem and outer sapwood beneath the bark. This early feeding disrupts the tree’s ability to transport sugars and nutrients.
As the larvae mature, they tunnel deeper, boring into the xylem and heartwood of the trunk and branches. This extensive tunneling creates large galleries, physically weakening the tree and cutting off the flow of water. This damage leads to branch dieback and eventual tree mortality. The life cycle, which often takes one to two years, is spent almost entirely inside the wood, where the larvae grow up to two inches long.
Adult beetle feeding is far less destructive, serving mainly to provide energy for mating and egg-laying. Emerging adults chew on the bark of small twigs and branches or feed on the leaf petioles. This superficial feeding, called maturation feeding, is necessary for the female to fully develop her eggs before she chews an oviposition pit into the bark.