#ash tree

June 2026

The manna ash or South European flowering ash (lat. Fraxinus ornus) is in bloom. It must have faded by now, but I really wanted to show it to you😻

ASH.

I'll be honest: I didn't really start paying attention to our ash trees until we lost one. It was a large white ash at the back of the property, probably 18 inches in diameter, and it went from "maybe a little thin up top?" to full canopy collapse in two seasons. By the time I called anyone, the verdict was that it had been infested for at least three years before the symptoms became obvious enough for me to notice.

Since then I've been paying closer attention to the other ash trees on the block. We have two more in our yard and there are several more on the neighbors' properties and along the street. Monmouth County has a lot of mature ash, and emerald ash borer is established here, so the watch doesn't really end. What I've learned over a few years of paying attention is that the signs are different depending on when you look, and you will miss almost everything if you only look once a season or only look when something looks wrong.

This is what I've learned to look for, organized by season.

Photo by Magda Ehlers on Pexels

Spring: The Flush and the Bark

Spring is the season I now take most seriously, even though there's usually nothing dramatic to see. In late April, before leaves come in, I walk around each ash tree and look at the trunk and main branches for anything unusual. Bark that's splitting vertically in patterns that don't follow the normal diamond fissuring. Subtle ridging or waviness that follows a curved path, which can indicate that a larval gallery beneath has been pushing against the bark from inside.

Once leaves start coming in, I watch the flush. A healthy ash tree leafs out pretty evenly. The first year I understood what to look for, I noticed that one of our remaining ash trees was significantly thinner at the top during leafing out while the lower half was filling in normally. I wasn't sure if it meant anything but I took a photo and made a note.

The bark peel test is the most useful spring step. If there's any section of bark that's starting to lift slightly, I peel a palm-sized piece. Beneath the bark of an infested tree you find S-shaped channels packed with fine frass. This is unmistakable once you've seen it. On our surviving ash trees I've found clean wood beneath the bark so far, but I do the test every spring at two or three points on each tree.

Rutgers Cooperative Extension has good resources on ash tree health and EAB management for New Jersey homeowners that are worth bookmarking.

Summer: When the Canopy Tells Its Story

Midsummer is when EAB-infested trees reveal the accumulated damage from the previous season's larval feeding. The pattern to watch for is dieback that starts at the top and outer crown and works its way down. If the upper third of the crown is thinning while the lower half looks normal, that's the signature pattern.

The summer I lost the first ash tree, I remember thinking the top looked "tired." That was probably late July or early August. By September the upper half was dead. In retrospect I had another full growing season before that to have caught it, and another before that to have treated it.

The two secondary signs I watch for in summer are:

Epicormic sprouts. Little bushy clusters of new shoots pushing directly from the bark of the lower trunk or main branches. A healthy ash doesn't do this. When a tree does this in combination with upper-crown thinning, it means the tree's vascular system is compromised and it's trying to compensate below the damage zone.

Woodpecker activity. Birds foraging on the trunk, particularly if they're creating concentrated clusters of holes or actually scaling off sections of outer bark, usually means there's something under there worth eating. I've had neighbors ask me why the woodpeckers were so interested in a particular tree. That's usually a reason to look at the bark more carefully.

The International Society of Arboriculture notes that woodpecker activity on ash trees often predates visible canopy symptoms by one to two full seasons. I've found that a useful frame: if the birds are showing unusual interest, don't wait for the canopy to confirm it.

Fall: Early Color and Canopy Density

By September I take stock of how the canopy density compares to previous years and to comparable trees in the area. Ash trees infested with EAB often show early fall color change, sometimes two to four weeks before uninfested ash trees of the same species.

I've started using the photos I take each year to compare. The difference between a tree's crown density in September compared to the previous September is something you notice more clearly in a side-by-side photo than just looking at it fresh. One of our surviving trees showed about 20 percent thinner crown density in this comparison last fall. When I brought local arborists out to assess it, the verdict was early-to-moderate infestation still within the treatment window, which we went ahead with.

Fall bark peeling also works well. Galleries are still clearly visible in October in New Jersey temperatures. Larvae may still be present if you peel bark in early fall.

Winter: The Clearest View

After leaf drop, the structure of the canopy is fully visible. This is actually the easiest time to see dieback that you might have missed during the growing season, because the dead branches are obvious against the sky.

I walk around our ash trees in December and look at the crown silhouette from several angles. Dead branches in the upper crown hold their structure but look stiff and dry without the budding you see on healthy dormant branches. Woodpecker damage is also most visible in winter. Patches of lighter inner bark where a bird has scaled away the outer surface stand out clearly without foliage in the way.

Winter is also when I count exit hole density on any sections of the trunk I can reach closely. Lots of D-shaped holes, each roughly 1/8 inch across, in a concentrated area is a sign of multi-year infestation. Finding a few scattered holes is a reason to be watchful; finding them densely packed is a reason to make calls before spring.

Photo by Heru Vision on Pexels

What I'd Tell Anyone With Ash Trees

The most important thing I've learned is that the window to do something about EAB infestation is longer than the window to notice the problem without paying close attention. The tree I lost was probably treatable two seasons before I called anyone. The trees I still have are still alive partly because I'm now looking at the right things at the right times of year.

If you have mature ash trees in Monmouth County, especially white ash or green ash, start a seasonal inspection habit now. The NJ DEP Division of Parks and Forestry has resources for homeowners on EAB and other tree pest issues specific to New Jersey. Rutgers extension is also excellent for local guidance.

Emerald ash borer is established throughout New Jersey, and Monmouth County ash trees have been in the pest's range long enough that the question is rarely whether they could become infested and more often whether they already are. The practical challenge is that EAB spends most of its life beneath the bark, and the signs it leaves change significantly depending on the time of year you are looking.

This checklist is designed to help homeowners with ash trees on their property stay ahead of infestation rather than responding after the damage becomes obvious. Each seasonal step is brief and requires no special equipment beyond a pocketknife or strong fingernail for bark peeling and a flashlight for low-light conditions.

Photo by Diogo Miranda on Pexels

Before You Start: Identify Your Ash Trees

Not all trees that look similar to ash are ash. Before you begin monitoring, confirm which trees on your property are ash species. Ash (Fraxinus) can be identified by:

Compound leaves with five to nine leaflets arranged in opposite pairs along a central stem

Opposite branching pattern (branches, twigs, and buds directly across from each other, not alternating)

Diamond-pattern bark on mature trees, a distinctive interlocking fissured pattern

Winged seed clusters (samaras) that hang in clusters and persist into fall and winter

Green ash (Fraxinus pennsylvanica) and white ash (Fraxinus americana) are the most common species in Monmouth County residential landscapes. Both are equally susceptible to EAB. The Rutgers New Jersey Agricultural Experiment Station has tree identification guides that cover both species in detail.

Spring Checklist (Late April to Early May)

Before leaves emerge:

[ ] Walk around each ash tree and look at the main trunk from multiple angles. Check for vertical bark splits or cracks that run along the trunk in patterns different from the normal diamond fissuring of mature ash bark.

[ ] Look for subtle ridging or wavy texture on bark sections, particularly S-shaped patterns that curve rather than running straight. These can indicate larval galleries beneath.

[ ] Check for D-shaped exit holes from the previous year's adult emergence. These are roughly 1/8 inch across with a distinctly flat edge on one side. Use a flashlight in shadowed areas of the lower trunk.

[ ] Identify any sections of bark that are lifting slightly at the edges or feel loose when you press them.

During leaf flush:

[ ] Check the canopy as it leafs out. Are all parts of the crown filling in at the same rate? Sparse or delayed flush in the upper crown compared to the lower crown may indicate vascular disruption from EAB galleries above.

[ ] Compare your ash trees to comparable ash trees in the neighborhood. Significant differences in flush quality between similar trees are worth investigating.

Late Spring Checklist (Late May to June)

Peak bark examination window:

[ ] Use a pocketknife or strong fingernail to peel a palm-sized section of bark on the main trunk, one on a major scaffold branch, and one on the upper trunk if accessible. The outer bark should peel away relatively easily during the active growing season.

[ ] Look at the wood surface beneath the peeled bark. S-shaped galleries, sinuous channels three to five millimeters wide packed with fine tan frass, indicate active or recent EAB infestation. Clean, smooth wood beneath the bark indicates no current gallery activity at that location.

[ ] Look for fresh D-shaped exit holes in the lower trunk and scaffold bark. Fresh holes have clean, sharply cut edges; older holes are weathered and may show lichen growth at their margins.

[ ] Look for fine frass on the bark surface near exit holes or at the base of the trunk. EAB frass is fine-textured and tan to reddish-brown.

Summer Checklist (July to August)

Canopy assessment:

[ ] Stand back far enough to see the full crown of each ash tree. Does the upper crown look noticeably thinner or more open than the lower crown? Concentrated dieback in the upper third of the crown is a characteristic EAB presentation.

[ ] Look for dead branch tips in the upper crown, individual branches that are clearly dry with no foliage and no green buds remaining.

[ ] Look for epicormic sprouts: small, bushy clusters of new growth pushing directly from the bark of the lower trunk or the bases of major scaffold branches. These indicate significant vascular disruption above.

Indirect indicators:

[ ] Has woodpecker activity on the tree increased compared to previous years? Clusters of small rectangular holes on the trunk, or areas of bark that have been scaled away exposing lighter inner bark beneath, indicate that birds are foraging for larvae.

[ ] Note whether the overall canopy density looks similar to previous years or noticeably reduced.

If you see significant upper-crown dieback in summer, consult a professional promptly. Treatment options for EAB become limited once canopy loss exceeds about 50 percent. The International Society of Arboriculture provides guidance on EAB treatment thresholds and what qualifies a tree as still within the viable treatment window.

Fall Checklist (September to October)

Color and density comparison:

[ ] Is your ash tree showing fall color earlier than comparable ash trees in the neighborhood? EAB-stressed ash trees often change color two to four weeks before uninfested trees.

[ ] Compare this year's canopy density in October to your photos from the same month last year. A measurable reduction in overall leaf density from year to year is a warning sign.

[ ] Peel bark in one or two locations during September or early October. Galleries remain visible in fall. Larvae may still be present in early fall before they enter dormancy.

Winter Checklist (November to March)

Structural view:

[ ] Look at the full crown silhouette with all foliage gone. Dead branch structure in the upper crown is clearly visible. Dead branches are stiff and may still have gray or brown bark attached, but they lack the small buds visible on healthy dormant branches.

[ ] Look for blonding on the bark: patches where the outer bark has been scaled away by woodpeckers, exposing the lighter cream or golden inner bark beneath. Blonding across a significant section of the trunk indicates heavy woodpecker foraging and probable larval density.

[ ] Count D-shaped exit hole density on sections of trunk you can examine closely. More than five holes per square foot in any area indicates a tree that has been infested for multiple seasons.

Documentation:

[ ] Take a canopy photo from the same position and approximately the same time as previous years to build a year-over-year comparison record.

[ ] Note any changes in structural conditions (split branches, trunk wounds, changes in lean) that may affect overall risk.

When the Checklist Points to Professional Assessment

If any of the seasonal checks produce positive findings, including galleries under the bark, D-shaped exit holes, significant crown dieback, or heavy woodpecker foraging, the next step is a professional evaluation. The treatment window for systemic insecticide is determined by how much of the canopy remains functional. An assessment that establishes the current infestation stage determines whether treatment, removal, or no intervention is the appropriate path.

For property owners in the Middletown and Monmouth County area, a Monmouth County tree service experienced with EAB can provide an on-site assessment and walk through the options with you. The NJ DEP Division of Parks and Forestry also maintains resources for homeowners dealing with EAB and other invasive forest pests in New Jersey.

The seasonal checklist takes about twenty minutes per tree, twice through the growing season, plus a winter walk-around. For mature ash trees that would cost several thousand dollars to remove and replace, twenty minutes a season is a worthwhile investment.