Emerald Ash Borer: What to Know About the Beetle

The emerald ash borer – a metallic green beetle – is a serious threat to ash trees. This wood-boring beetle’s effects are similar to that of Dutch elm disease and chestnut blight. In forests, as ash trees die, it leaves behind gaps in forest canopy, which allows light to reach the underlying vegetation.  

Ash trees in lawns too are susceptible to attacks by emerald ash borer. As a lawn owner, if you think you have ash trees, it’s important to protect them against emerald ash borer damage. This post offers an insight into the green beetle and the damage it causes. 

What is an Emerald Ash Borer? 

The scientific name of emerald ash borer is Agrilus planipennis. The emerald ash borer (EAB) feeds on species of ash trees. The beetles reproduce inside the bark – they lay eggs within crevices of the bark, especially on ash trees. The larvae of EAB feed beneath the ash tree bark and they take around two years to grow into adults.  

In their land of origin, EABs were not very destructive, but outside their native range, it has been seen that the beetle is an invasive species, being highly destructive for ash trees.  

Adult ash borers are about 1.6 millimeters wide and 8.5 millimeters long and are bright metallic green in color. The EABs possess a characteristic making them unique. The beetle is North America’s sole species of its kind that has a bright red-colored upper abdomen when you view it with its elytra and wings spread.  

How Harmful are EABs to Ash Trees?  

This green colored beetle attacks all ash tree species native to the US and native white fringetree. They can attack both unhealthy and healthy trees. However, Mountain Ash – not considered to be a true ash – doesn’t have susceptibility to emerald ash borers.  

Adult EABs lay their eggs on ash tree bark. When these eggs hatch, the immature beetles or the larvae bore into the tree bark and start feeding on the tree’s transportation tissues. This leads to disruption of the movement of water and nutrients within a tree, which in turn results in girdling it and causing death of the tree.  

Emerald ash borer can naturally spread by flying to new ash trees; however, such dispersal is confined to a few miles per year. Long-distance dispersion is a more threatening spread, which can happen easily when an EAB is transported accidentally from an infested region to an uninfested region through transportation of products made of ash wood by humans.  

How to Identify Emerald Ash Borer? 

The ash borer burrows into trees and feeds on its nutrients, leading to tree death. The beetles lay larva in the tree bark. They can reproduce as well as spread quite rapidly. Detecting the pest can be difficult in the early infestation stages, but there are some signs and symptoms of EAB as mentioned below: 

Adults or larvae 

Larvae are cream-colored and are found feeding underneath the bark. They are flattened slightly and at their abdomen, the larvae comprise pincher-like appendages. An adult emerald ash borer has a body in the color of coppery green or shiny emerald. It has large eyes that are black or bronze and kidney-shaped. It has a narrow body, with a length of 7-8 mm and width of 3-3.5 mm.  

D-shaped holes in bark 

When an adult EAB exits an ash tree, it leaves behind an exit hole in the bark that’s D-shaped. Such D-shaped holes are a unique feature associated with the group of beetles to which the emerald ash borer belongs.  

S-shaped tunnels beneath the bark 

When the larva of ash tree borer feeds beneath the bark, it creates a path that’s S-shaped as it travels up or down the ash tree.  

Epicormic shoots 

Epicormic shoots develop from the trunk of a tree when it is under stress. You can sometimes find them on larger branches and in the crown of a tree. Epicormic shoots are not developed by all trees infested with EAB. However, these shoots can grow quickly under the right conditions. These shoots are also referred to as witches brooms, water sprouts, and suckers. 

Woodpeckers 

If you find increased woodpecker activity, check out for EABs. Woodpeckers feed on the ash borer larvae present under the bark.  

Leaf notches 

Adult EABs feed on the leaves of ash trees and cut notches on leaf sides. When there is a high beetle population, there will be a noticeable defoliation.  

Vertical bark splits 

It’s common for infested trees to feature bark cracks and deformities on the branches and trunk.  

Branch death from the top down 

When beetles feed, the branches are eventually killed. As the branches die, the foliage becomes yellow, wilts, and then falls off leaving behind bare branches. 

How do you Know if you have an Ash Tree in your Lawn? 

Emerald ash borer attacks ash trees’ four species – blue, black, white, and green ash. As mentioned before, mountain ash – another ash tree species – is not attacked by EAB. Any other species of trees has not been attacked by EAB till date in North America. If you want to identify whether you have an ash tree in your lawn, here are some characteristics to look for: 

Seeds 

Seeds, when present on the trees, are oar-shaped, dry samaras. The seeds occur in clusters usually and hang on trees until early winter or late fall.  

Bark Patterns 

Bark is tight on mature ash trees with a unique pattern of diamond-shaped ridges. The bark is smoother on young ash trees. 

Opposite Branching 

Ash trees feature opposite branching. In these trees, the branches are across from one another directly and are not staggered. As limbs may break off or die, every branch may not consist of an opposite mate. Moreover, the color of the branches is gray to brown and they don’t comprise a waxy coating. 

Leaves 

The leaves of ash trees are compound and comprise 5-11 leaflets. Leaf margins can be toothed or smooth with a bud at the branch’s end. (Boxelder is the only other type of oppositely sided tree having compound leaves and is mistakenly believed to be an ash tree at times.) 

Other trees resembling ash trees include – shagbark hickory, European mountain ash, black walnut, elm, and boxelder tree. 

Wrap Up 

If you have one or more ash trees in your lawn, it’s important to take steps to protect your trees from emerald ash borer damage. Preventative treatment is required for this and is the sole way of avoiding the expenses associated with cutting, removal and disposal of dead ash trees.  

All American Turf Beauty is a reputed lawn care company based in Iowa that has expertise in emerald ash borer treatment. Our well-experienced lawn care professionals can apply the right preventative treatment options to save your ash tree from the attack of emerald ash borer. Get in touch with us today to avail quality emerald ash borer treatment and keep your ash tree in sound health!