What Are These Bugs on My Tree?

Understanding Common Summer Tree Pests in Northwest Indiana

Summer is a time of explosive growth—for both trees and the insects that feed on them. As

Pine Needle Scale on Scotch Pine

the temperatures rise and canopies fill in, many homeowners start to notice activity on the leaves, stems, and bark of their landscape trees. Insects are part of every healthy ecosystem, but when populations surge or when trees are stressed, even common pests can tip the scales from harmless to harmful.

In this post, we’ll break down the most frequently encountered tree pests in Northwest Indiana during the summer months, explain what’s happening from a tree health perspective, and offer insight into when it’s time to take action.

The Importance of Context in Pest Identification

First, it’s worth noting that not all insects are harmful, and even damaging ones don’t always require intervention. Trees have evolved complex defense systems—including chemical responses and resource compartmentalization—to tolerate some level of herbivory. But when environmental stress (like drought or poor soil conditions) weakens those defenses, pest activity can escalate into decline or dieback.

When we inspect a tree for pests, we consider:

• The species and age of the tree

• Recent stress events (transplanting, drought, construction)

• Presence of natural predators

• Timing of insect development (life stage)

• Evidence of systemic infestation vs. superficial feeding

With that in mind, here are some of the most common pests we see each summer:

Japanese Beetles (Popillia japonica)

Identification: Metallic green body with copper-colored wing covers.

Japanese Beetle feeding on foliage

Active period: Late June through August

Host species: Linden, crabapple, birch, elm, cherry, apple, and roses

Japanese beetles are one of the most visually obvious pests. Adult beetles emerge from the soil in early summer and feed voraciously on foliage, creating a distinct “skeletonized” appearance where only the leaf veins remain. Although a single season of damage may not kill a healthy tree, multiple years of defoliation can lead to significant energy loss and reduced resilience.

Complicating the issue, the larvae (grubs) feed on turfgrass roots, creating a dual impact on both your trees and lawn. Treatment may involve both foliar sprays (to suppress adults) and soil-applied insecticides in early fall (to target grubs).

Aphids (various species)

Identification: Tiny, soft-bodied insects (green, black, or brown), often found in colonies on new growth

Active period: May through September

Aphids feeding on Spruce needles

Host species: Maple, ash, birch, tulip tree, and many ornamentals

Aphids feed by piercing the phloem and drawing out sugary sap. The result is distorted or curled leaves, yellowing, and sometimes premature leaf drop. Their excrement—called honeydew—creates a sticky residue that can coat cars, sidewalks, and patio furniture. Where honeydew accumulates, you’ll often find sooty mold—a black fungus that grows on the sugar, not the tree itself, but can block sunlight from reaching leaves.

Aphid populations often build rapidly in warm, still conditions. In healthy landscapes, predators like lady beetles and lacewings usually keep them in check, but on younger trees or in drought-stressed canopies, suppression may be necessary.

Leafhoppers (family Cicadellidae)

Identification: Small, wedge-shaped insects that move sideways or jump quickly

Active period: Late spring through mid-summer

Host species: Redbud, maple, honeylocust, fruit trees, and ornamentals

Leafhoppers on Rose leaves

Leafhoppers feed on xylem and phloem fluids and are known for causing stippling damage—tiny white or yellow specks on the surface of leaves. In larger populations, they can also cause "hopperburn", a condition where leaf edges dry and curl due to toxic saliva introduced while feeding.

While the physical damage is rarely significant enough to threaten tree survival, the bigger concern is pathogen transmission. Certain species of leafhoppers can vector plant diseases, such as X-disease in stone fruit or aster yellows in flowering perennials.

Scale Insects (various species)

Identification: Stationary, waxy bumps along stems and branches

Active period: Crawlers emerge in June–July

Host species: Maple, magnolia, dogwood, oak, and many landscape ornamentals

Magnolia Scale feeding on Magnolia twigs

Scale insects are often overlooked because of their sedentary nature. But don’t be fooled—under those waxy shells, scale insects are actively feeding on sap. Like aphids, they excrete honeydew, which leads to sooty mold and sticky surfaces.

The most vulnerable life stage is the crawler phase, when newly hatched scale insects move across bark in search of a feeding site. This is the ideal window for treatment, usually mid-to-late summer. Dormant oil applications in early spring can also help reduce overwintering populations.

Ants harvesting honeydew from Aphids

Ants – A Symptom, Not the Cause

If you notice ants marching up and down your tree, they’re usually not the primary pest—but they’re often an indicator that aphids or scale are present. Ants protect these sap-sucking insects in exchange for honeydew, forming a mutually beneficial relationship that can actually increase pest survival.

Controlling the root issue (aphids or scale) will usually cause the ants to disappear.

Why Monitoring Matters More Than Spraying

Tree pest management is not about eliminating all insects—it’s about keeping populations in balance. Blanket insecticide applications can disrupt that balance by removing beneficial predators and pollinators, sometimes worsening the problem long-term.

At NWI ArborCare, we use Integrated Pest Management (IPM) principles to:

• Monitor pest populations over time

• Determine treatment thresholds

• Apply targeted, environmentally responsible controls

• Strengthen the tree’s overall health through proper soil, water, and pruning care

Noticing Damage? Here's What to Do

If you’re seeing:

• Chewed leaves or skeletonization

• Sticky residue or black mold

• Bumps or clusters on twigs

• Ants crawling persistently up trunks

…it’s time to schedule a tree health inspection. Pest problems are best addressed early in the season, when populations are manageable and tree defenses are still intact.

Call 219-240-0460 or visit nwiarborcare.com to book a consultation with a certified arborist.