Late Summer Tree Pest Control: August Threats and How to Manage Them

As temperatures soar and rainfall dwindles, trees face mounting stress in August. While homeowners often focus on watering and sun exposure, another threat quietly creeps in during late summer: pests. Insects like borers, aphids, and scale thrive in hot, dry conditions—taking advantage of weakened trees and setting the stage for serious damage.

This guide by TreeNewal explores the most common August tree pests, signs of infestation, and how professional, eco-conscious strategies—especially those used by ISA Certified Arborists—can help you protect your trees and preserve your landscape.

Why August Is Peak Pest Season

August is a pivotal month for tree health. Long stretches of dry heat create ideal breeding conditions for pests and compromise a tree’s natural defenses. Here’s why pest activity spikes in late summer:

• Accelerated life cycles: Many insect pests reproduce faster in warm temperatures, increasing their populations dramatically.
• Drought stress: Trees struggling with heat and limited water become easier targets for boring insects and sap-sucking pests.
• Cumulative damage: Trees already impacted by early summer infestations may decline further if additional pests arrive in August.
• Urban heat islands: Concrete and asphalt surfaces radiate heat, intensifying pest pressure in residential areas.

In short, August is when trees are most vulnerable—and when pests are most aggressive.

Most Common Tree Pests in August

Understanding which pests are active during this time helps you stay ahead of potential problems. Here are the top offenders to watch for when it comes to tree pest control in August:

1. Borers

Examples: Emerald Ash Borer, Flatheaded Appletree Borer, Southern Pine Beetle

Borers are among the most destructive pests to trees. These insects lay their eggs in bark crevices. Once hatched, larvae tunnel into the trunk, disrupting the tree’s vascular system.

Signs of borer infestation:

• D-shaped or round exit holes in bark
• Frass (sawdust) near the base
• Thinning canopy or dieback in upper limbs
• Bark splitting or oozing sap

Unchecked, borers can kill a mature tree within a few seasons.

2. Aphids

Tiny but prolific, aphids cluster on leaves and stems, feeding on sap and secreting a sugary substance called honeydew.

Signs of aphid activity:

• Curling or yellowing leaves
• Sticky residue on leaves, cars, or patios beneath the tree
• Presence of black sooty mold (fungus that grows on honeydew)
• Ants climbing the tree to feed on the honeydew

While usually not fatal, large infestations weaken trees and attract secondary pests and diseases.

3. Scale Insects

Scale insects attach to branches or leaves and feed without moving, often appearing like small bumps or growths.

Types: Soft scale, armored scale, cottony cushion scale

Signs of scale infestation:

• Yellow or wilted leaves
• Dieback on branches
• Sticky honeydew and sooty mold
• Clusters of small, shell-like insects on bark or leaves
• Scales are notoriously difficult to spot until the damage becomes significant.

4. Spider Mites

These pests thrive in hot, dusty environments and can defoliate trees if left untreated.

• Signs of spider mite presence:
• Fine webbing on leaves or branches
• Tiny white or yellow stippling on foliage
• Leaves may appear bronzed or scorched

Often mistaken for drought stress, mite damage is widespread in August due to dry conditions.

5. Caterpillars and Leaf Miners

While not always active in high heat, some caterpillar and leaf miner species continue feeding into late summer.

Signs include:

• Chewed or skeletonized leaves
• Tunneling patterns between leaf layers
• Premature leaf drop

These pests reduce a tree’s ability to photosynthesize, weakening it going into fall.

Signs of a Tree Pest Infestation

Even if you can’t identify the pest directly, trees offer visual clues that something’s wrong. Keep an eye out for:

• Leaf discoloration: Sudden yellowing, browning, or spotting
• Sticky residue or mold: Often a sign of aphids or scale
• Visible insects: Look on undersides of leaves and branches
• Frass: Sawdust-like material around the base or bark
• Wounds or oozing sap: Indicators of boring insects
• Unseasonal leaf or fruit drop: Can mean infestation or systemic stress
• Ants or wasps: Often attracted by sugary honeydew

Early detection is key. The sooner you spot these signs, the more effective treatment will be.

How an ISA Certified Arborist Can Help

For long-term, eco-conscious pest control, professional support is often the smartest move—especially in August, when timing and treatment method matter most.

Here’s how an ISA Certified Arborist approaches tree pest control in August:

1. Accurate Diagnosis

An arborist can differentiate between environmental stress and pest damage, ensuring that treatment is targeted and effective. Misidentifying the issue can lead to wasted time or harm to beneficial insects.

2. Eco-Friendly Treatment Options

Rather than defaulting to chemical sprays, certified arborists use integrated pest management (IPM) strategies, such as:

• Horticultural oils: Suffocate pests and eggs without damaging the tree or surrounding soil
• Insecticidal soaps: Effective against aphids and mites, with minimal environmental impact
• Beneficial insects: Introducing ladybugs or parasitic wasps to naturally reduce pest populations
• Trunk injections: Deliver treatment directly into the tree’s system—ideal for borers and scale

3. Tree Health Support

Pests are more likely to attack stressed trees. Arborists address the root cause by:

• Aerating compacted soil
• Applying nutrient-rich mulch
• Ensuring proper watering practices
• Pruning out infested or dead limbs

4. Monitoring and Prevention

An arborist can set up seasonal pest monitoring, helping you stay ahead of infestations with scheduled checkups and maintenance.

When to Seek Professional Help

Call in a certified arborist if you notice any of the following:

• Rapid dieback or canopy thinning
• Repeat infestations year after year
• Large pests or extensive damage
• Difficult-to-access trees (tall, near power lines)
• Concerns about chemical treatments affecting kids, pets, or pollinators

Late summer is not the time to wait and see—especially with borers or scale. Swift action saves trees and prevents infestations from spreading to nearby landscape plants.

Stay Ahead of August Pests

August may be the tail end of summer, but it’s the front line in pest management. Trees already stressed by heat and drought are especially vulnerable to borers, aphids, scale, and more. Spotting the signs early and taking appropriate action can prevent costly damage and keep your trees healthy heading into fall.
Partnering with an ISA Certified Arborist ensures you get expert evaluation and sustainable treatment options tailored to your trees and property.

Don’t Let Late Summer Pests Take Over

Concerned about tree pest control this August? Contact our certified team today to schedule a professional inspection and put your trees on the path to long-term health and resilience.