The box elder tree (Acer negundo) is a fast-growing, medium-sized deciduous tree. A member of the maple genus, it uniquely features compound leaves with three to seven leaflets. Adaptable to various soil conditions and climates, it thrives even in urban settings but is often considered “weedy” due to its rapid growth and brittle wood. Understanding its potential problems helps manage its presence and maintain health.
Identifying Common Pests
Several insect pests commonly affect box elder trees. Box elder bugs (Boisea trivittatus) are widely recognized, often gathering in large numbers on sunny surfaces. These half-inch long insects are black with distinctive orange or red markings, including three stripes behind their head and an ‘X’ pattern on their wings. They feed on sap from developing leaves and seeds, causing minor deformities or yellow spots on foliage, though significant tree damage is rare.
Aphids, another sap-feeding pest, are found on the underside of leaves and new shoots. Their feeding leads to curled or distorted leaves and a sticky honeydew residue, which can promote sooty mold growth. Box elder twig borers target buds and tender shoots. Their activity causes trees to develop a bushy appearance and lose their natural shape, as they bore into twigs, making them difficult to control once inside.
Recognizing Common Diseases
Box elder trees are susceptible to several diseases. Powdery mildew, a common fungal disease, appears as white to grayish, powdery spots on leaves, stems, and sometimes flowers. Severe infections can lead to leaves yellowing, curling, or dropping prematurely, but rarely cause tree mortality. This fungus thrives in humid conditions, especially with cool nights followed by warm days.
Verticillium wilt, caused by a fungus (Verticillium dahliae or Verticillium albo-atrum), is a serious concern for maples, including box elder. Symptoms include sudden wilting of individual branches, often on one side, followed by yellowing and browning foliage. The sapwood under the bark may show dark or olive green discoloration, indicating blocked water flow. Cankers, sunken lesions on branches or the trunk, can also affect box elder trees, potentially leading to branch dieback and hindering growth.
Addressing Environmental and Structural Challenges
Box elder trees are known for their brittle wood, making them prone to damage from wind, ice, and snow. Their irregular form and tendency to grow multiple trunks contribute to structural instability, with large branches sometimes bowing or breaking. Improper planting, such as planting too deeply or in unsuitable soil, can lead to issues like root rot or girdling roots, restricting water and nutrient uptake.
Soil conditions also significantly impact tree health. Compacted soil can restrict root growth and water penetration. Nutrient deficiencies, often indicated by discolored or malformed leaves, can arise from poor soil quality. Environmental factors like prolonged drought or severe frost can stress the tree, leading to decline or increased susceptibility to pests and diseases.
General Management and Prevention Strategies
Maintaining box elder tree health involves consistent care. Proper watering is important, especially for newly planted trees or during dry periods, with a general recommendation of watering once every one to two weeks for deep soil penetration. Mulching around the base helps retain soil moisture, regulate temperature, and suppress weeds, mimicking their natural woodland environment.
Pruning, best done in late winter or early spring when dormant, helps maintain shape, improves air circulation, and removes dead, damaged, or crossing branches. Regular removal of suckers and sprouts from the tree’s base and main branches contributes to structural integrity and appearance. Removing fallen leaves and debris around the tree reduces the risk of fungal infections and deters pests.
Knowing When to Call an Arborist
Professional intervention from a certified arborist is advisable in certain situations. If a box elder tree shows signs of severe disease, such as extensive wilting, widespread discoloration, or significant fungal growth on the trunk, an arborist can provide an accurate diagnosis and treatment recommendations. They can also assess structural concerns, including large cracks, sudden leaning, or extensive dead or broken branches, especially after a storm.
Arborist expertise is valuable for large limb removal, complex pruning, or when a tree poses a safety concern. Consulting an arborist ensures long-term tree health and prevents potential hazards, as they provide comprehensive assessments and recommend appropriate actions.