Common Problems With Box Elder Trees and How to Handle Them

The box elder tree, Acer negundo, is a fast-growing and widespread deciduous tree native to North America. Its ability to thrive in various conditions has made it a common sight, but it is often viewed as a problem tree by homeowners. Its rapid growth, specific pests, and susceptibility to certain diseases and structural failures can create a range of challenges. Understanding these potential issues is the first step in managing this resilient tree.

Common Pest Infestations

The most notable insect is the boxelder bug (Boisea trivittata). These black and red insects feed on the leaves, stems, and seeds of the tree, particularly favoring female, seed-bearing trees. While they rarely harm the tree’s health, they are a nuisance to humans, congregating in large numbers on sunny surfaces during autumn to seek warmth.

This behavior leads them to invade homes and sheds for shelter, entering through small cracks in the foundation or siding. Once inside, they can stain fabrics and release an unpleasant odor when disturbed. While these trees can also host other pests like aphids, the invasive nature of boxelder bugs makes them the primary pest concern for homeowners.

Fungal Diseases and Cankers

Box elder trees are susceptible to fungal diseases that affect their foliage, especially during cool, wet spring weather. Powdery mildew appears as white, dusty patches on the leaves, which can hinder photosynthesis. Anthracnose is another fungal issue, causing dark, sunken lesions on the leaves, leading to distortion and premature leaf drop.

More serious conditions can also affect the woody parts of the tree. Cankers, which are dead sections of bark on branches or the trunk, can develop from fungal infections and may girdle and kill limbs. In older or damaged trees, heart rot fungus can invade the core of the trunk and major branches. This decay compromises the tree’s structural integrity from the inside out, often with few external symptoms until a major branch fails.

Inherent Structural Weaknesses

A significant drawback of the box elder is its physical structure, characterized by soft, brittle wood. This weakness makes the tree highly prone to breaking during storms, with wind and ice loads easily snapping branches. This susceptibility poses a risk to property and safety, especially for trees located near homes or driveways. The damage can range from minor limb loss to failure of the main trunk.

The tree’s rapid growth contributes to these structural problems, often resulting in a sprawling, irregular form with weak branch attachments. Furthermore, female trees produce a massive quantity of winged seeds, known as samaras, each year. These seeds create a significant mess, clogging gutters and sprouting into a thicket of unwanted seedlings throughout lawns and garden beds, adding to the tree’s reputation as weedy and high-maintenance.

Managing Box Elder Tree Issues

Addressing the problems associated with box elder trees involves a combination of preventative measures and targeted actions. To manage boxelder bugs, focus on sealing potential entry points into your home, such as cracks in the foundation, gaps around windows, and utility line entrances. Reducing their food source by promptly cleaning up fallen seeds can also help limit their population outdoors. For foliar diseases like powdery mildew, improving air circulation through selective pruning can be beneficial.

For the tree’s structural issues, proper pruning is a management strategy. Engaging a certified arborist to perform corrective pruning on young trees can help develop a stronger, more resilient structure. This involves removing weak, poorly attached branches and encouraging a dominant central leader. For mature trees that pose a significant risk due to weak wood or internal decay, removal is the safest course of action, particularly if they are situated near valuable property.