What you need to know about the Emer­ald Ash Borer and its man­age­ment

Ontario Gardener Magazine - - CONTENTS -

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.


Tun­nels cre­ated by the larva of the bee­tle.

The tell­tale exit holes of the bee­tle's larva.

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