What you need to know about the Emerald Ash Borer and its management
It’s making its way across Canada and has finally reached Winnipeg, travelling up from Minnesota. We are talking about the dreaded emerald ash borer, the imported, pretty, green jewel beetle that is devastating ash trees, particularly green ash, across central Canada and the U.S. It does not affect mountain ash.
Its Latin name is Agrilus planipennis and it arrived in Canada via Windsor in 2002. Since then, it has moved into Ontario and Quebec and hit Toronto in 2007 killing thousands of ash trees.
The beetle is about a half-inch long and an eighth of an inch wide. Its slender body is a metallic green in colour. The larvae are flat and white and an inch long.
The adult beetle, which is a flyer, feeds on leaves and then bores into the cracks in the bark of the tree to the cambium layer where it lays its eggs from June to August. The larva hatch and feed on the inner bark, creating tunnels that cut off water and nutrient flow in the tree and causing affected branches to die.
The damage starts in the crown which will exhibit thinning and dieback. Notches that look like bites out of the leaf will appear on an attacked tree and as time progresses you may see frass (worm poop) on these more severely eaten leaves. You might see sprouting of new branches in the lower part of three tree. Trees under attack will also send out heavy seed crops and foliage will yellow early.
To protect your trees, look for bark splitting and borer holes, which are D-shaped and about one-eighth inch across. If you peel back the bark, you will see the S-shaped larva galleries.
In Ontario, the only product used to treat infected ash trees is Treeazin, a neem derivative. This is also being heavily marketed in Manitoba. Injections are expensive and must be repeated several times every two or three years but most trees up to one-third impacted can be saved. A average single treatment costs between $200 and $300, but can go as high as $700 depending on the size of the tree.
Imidacloprid is a nicotinoid that is still in use in Quebec and Western Canada where it is used in crop management but it is likely that it will be phased out as early as next December, 2018 over concern about detrimental effects on fish and wild birds.
It is also injected in trees but has sometimes been used as a soil drench around the roots of the tree. It can take up to two months for the product to reach the crown of a tree.
The typical size of the beetle.
Larva of the Emerald Ash Borer.
Tunnels created by the larva of the beetle.
The telltale exit holes of the beetle's larva.