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Know your ash

May 31, 2011

Take a look outside. The color green probably fills some, if not most, of your view. Leaves of many shapes, sizes and shades once again burst onto the scene. Trees have come back to life. Do you know your ash trees?

Now more than ever it's important to get to know the trees on your property and in your community. Tree-killing invasive forest pests are on the move, and the best chance to protect trees is by detecting infestations early because this is when the chance of successfully managing the infestation is highest.

Beetle Detectives is a national call to action by the United States Department of Agriculture soliciting citizen assistance to survey trees in their backyards and look for signs and symptoms of a forest pest invasion. Landowners are often the first to notice dead and dying trees. The first step is knowing which trees are susceptible. Ash trees (Fraxinus spp.) are host to the emerald ash borer (EAB), a beetle from Asia staking its claim on ash trees in New York, 15 other states and two provinces. Once EAB invades an area, it can kill ash trees within three years.

Article Photos

Ash trees have opposite branching and compound leaves with 5-11 leaflets.
(Image courtesy of Keith Kanoti, Maine Forest Service,

Leaf arrangement, leaves and bark provide clues to tree identification. Three kinds of ash trees grow in New York: white (80 feet in height), green (60 feet) and black (30 to 50 feet). All ash stems and leaves are oppositely arranged, which means that leaves, buds and branches grow directly opposite from one another, rather than alternating or staggered.

Also, all ash have compound leaves. This means its leaf has more than one leaflet and all leaflets are attached to a single leafstem. The compound leaves of ash grow in a group of 5-11 leaflets, with one leaflet always growing at the very end. The leaflets may be either smooth or have slightly toothed edges.

The bark on a younger ash tree is relatively smooth, but as the tree ages the bark thickens and a unique diamond-like pattern in the raised bark is noticeable.

I went searching for ash trees on my property and was surprised to find 20. This could spell bad news for hazard trees after EAB invades. I examined each tree for signs of EAB attack: dieback in the crown of the tree, yellowing leaves, splitting of the bark, heavy woodpecker activity and stems or leaves growing out of the base of the tree. Seeing none of these symptoms, I then inspected the bark looking for the tiny D-shaped exit holes that the beetles leave upon emergence. I also looked for loose bark that could be peeled back revealing the signature S-shaped larval galleries beneath. Luckily I detected no signs of infestation, at least for now.

My last stop was to log on to and report that I searched my yard for signs of EAB damage. You can do this simple survey too then report it online under the organization name "New York-APIPP (Adirondack Park Invasive Plant Program."

We can take action. If each of us takes a moment to check our yards for ash and look for the signs of an EAB infestation, a large area can be surveyed! Beetle Detectives also has great information about searching your property for maple trees and other hardwoods at risk from another forest pest, Asian longhorned beetle (ALB).

Be on the lookout for EAB now through July. Adults are 3/8 to 5/8 inch long with metallic green wing covers and a coppery red or purple abdomen. If you think you see EAB, collect the insect and place it in a container in the freezer and call the Adirondack Park Invasive Plant Program at 518-576-2082.

Finally, when camping, only use firewood local to the area you are visiting to avoid transporting any insect hitchhikers that may be burrowed in the bark or wood. Firewood is the primary pathway of spread of forest pests.

Groups across New York are raising awareness about the value of trees to local economies, landscapes and the environment. Join the effort and get to know your ash!


Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at



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