Trees naturally interact with insects throughout the year, and in many cases, these pests cause little lasting harm. Effective tree care focuses on Integrated Pest Management (IPM) – an approach supported by the International Society of Arboriculture (ISA) that emphasizes monitoring, prevention, and informed action rather than routine treatment.  

Below are common tree pests that can typically be managed through IPM practices.  

Aphids 

Aphids are tiny insects that feed on plant sap and may cause leaf curling or sticky residue on foliage. While noticeable, they are often more of a nuisance than a threat to the overall health of established trees. 

Management: Monitoring leaf surfaces, rinsing foliage with water, and supporting beneficial insects (like ladybugs) usually keep aphid populations at acceptable levels. Higher populations of aphids mean more honeydew, and that can lead to sooty mold development, which could reduce photosynthesis by covering leaves. Consult with your arborist to determine if insecticidal management is warranted. 

Scale Insects 

Scale insects appear as small bumps on branches and stems and feed quietly over time. Heavy infestations may place added stress on trees that are already weakened.  

Management: Pruning infested areas when feasible, applying horticultural oils at the appropriate time, and maintaining good cultural practices help limit scale activity.

Hackberry Leafrollers 

Hackberry leafrollers are caterpillars that roll leaves together and feed inside them. Damage is typically seasonal and cosmetic; however, multiple years of defoliation may stress your tree. 

Management: Early detection – typically early in defoliation – is key. Most trees recover without treatment, though repeated defoliation may warrant a professional evaluation.  

Borers 

Borers are insects—most commonly beetles and moths —whose larvae tunnel into tree tissue, often targeting stressed or declining trees. Their presence is frequently a sign of an underlying health issue rather than the primary cause of decline.  

Management: Reducing stress through proper watering, soil care, and overall maintenance is the most effective way to prevent borer problems. Treatments are considered only when risk is high.  

Bagworms 

Bagworms attach small, bag-like coverings to branches and are most common on ornamental evergreen species such as cypresses and junipers. In heavily infested sites, they may move into neighboring deciduous species.   

Management: Removing and properly disposing of bags is the most effective approach. Routine inspection helps ensure early intervention. 

Spider Mites 

Spider mites thrive in hot, dry conditions and cause foliage to appear speckled or faded. Spider mites are tiny but can cause significant damage to leaves, mostly noted on cypresses, junipers and other ornamental evergreen trees and shrubs.  

Management: Regular inspection and reducing drought stress are key. Not all mite activity requires treatment. Consult with a professional to determine if your trees warrant treatment and can assist you with appropriate timing.  

Longhorn Beetles (Twig Girdlers) 

Twig girdlers cut small branches, commonly on elms, causing them to drop prematurely. While noticeable, damage is usually minor and temporary. 

Management: Collecting and discarding fallen twigs disrupts the insect’s life cycle and is usually sufficient.  

Invasive Pest: Emerald Ash Borer 

While most tree pests can be managed, some invasive species require a very different approach. 

Emerald Ash Borer (EAB) is an invasive, highly destructive insect that attacks ash trees. Unlike other pests, EAB cannot be managed once an infestation is established past a certain threshold.  

Prevention: The only effective way to protect ash trees is through preventive treatment, ideally prior to visible symptoms. Regular inspections and proactive treatment planning are critical for long-term ash tree survival.  

Strong Trees Are the Best Defense

IPM is built on the principle that healthy trees are more resilient to pests. Routine inspections, proper watering, and professional guidance help homeowners protect their tree while avoiding unnecessary treatments.