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Trees with Pest or Disease Infestations
in Rochester, NY
Monroe County has confirmed emerald ash borer, spongy moth, and thousand cankers disease across the area over the past 15 years. Rochester's older residential trees, many planted in the 1950s through the 1970s, are particularly vulnerable because they've been stressed by decades of drought, soil compaction, and poor pruning. A stressed tree can't fight off pests the way a healthy one can.
Quick Answer
Several invasive pests and diseases are active in Monroe County right now, and they can kill established trees within one to three years. Emerald ash borer and spongy moth are the most common ones causing visible damage in Rochester neighborhoods. Catching an infestation early makes treatment possible. Once a tree is more than half dead, treatment rarely saves it. Call (585) 565-4955 if you see thinning crowns or unusual bark damage.
Telltale Signs
Warning Signs to Watch For
- Crown thinning from the top down over one or two seasons
- S-shaped grooves under bark that peels away easily
- Unusually heavy caterpillar activity stripping leaves in summer
- D-shaped exit holes about 1/8 inch wide in the bark of an ash tree
- Dark sunken areas on the bark with cracks around the edges, called cankers
Root Causes
What Causes Trees with Pest or Disease Infestations?
Emerald ash borer infestation
Emerald ash borer larvae tunnel under the bark of ash trees and eat the layer that moves nutrients up and down the trunk. Monroe County has had confirmed infestations since around 2010, and untreated ash trees in Rochester neighborhoods die within 3 to 5 years of first infection.
The Fix
Systemic Insecticide Treatment or Removal
A systemic insecticide injected into the root zone moves through the tree and kills larvae before they can complete their damage. This only works if the tree still has at least half its canopy intact. Trees further gone need to be removed.
Spongy moth defoliation
Spongy moth caterpillars, which used to be called gypsy moths, go through boom cycles in the Rochester area and can strip every leaf off an oak or maple in a single summer. One defoliation stresses the tree. Two or three consecutive ones can kill it.
The Fix
Crown Spraying and Tree Health Program
Spraying in late May when caterpillars are small is the most effective window. A follow-up soil treatment supports root health so the tree recovers faster from defoliation stress.
Fungal canker disease
Wet springs — and Rochester gets them regularly — spread fungal spores that infect wounds and branch stubs left by bad pruning cuts. The fungus kills the bark in patches, cutting off nutrient flow to everything above the canker.
The Fix
Diseased Wood Removal and Pruning Wound Care
Infected limbs are cut back to clean, healthy wood. Pruning tools are disinfected between every cut so the fungus doesn't travel to the next branch. Healthy trees with good airflow resist reinfection better than crowded ones.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Emerald ash borer infestation | Spongy moth defoliation | Fungal canker disease |
|---|---|---|---|
| D-shaped holes visible in bark of a tree with compound leaves | |||
| Tree was completely stripped of leaves in June or July | |||
| Sunken, discolored patches on bark with cracks at the edges | |||
| Crown dying from top down with woodpecker holes in upper bark | |||
| Egg masses visible on bark or rocks near the tree in fall | |||
| Dead branches with streaked or discolored wood at the cut |
Free Inspection
Get a Diagnosis in Rochester
An on-site inspection is the only way to confirm which cause applies to your property. Free, no obligation.
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