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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis


Posted by John Fulton -

Here is a listing of common borers and their control times: Ash borers (early June and early July), Bronze birch borer (mid May and repeat two times at two week intervals), Dogwood borer (mid May and mid June), Flatheaded apple borer (late May and repeat in three weeks), Lilac borer (early June and early July), Locust borer (late August and mid September), Mountain ash borer (early June and mid July), Peach tree borer (mid June and mid July), Viburnum borer (early June and early July), and Zimmerman pine moth (April or August). The Emerald ash borer, although not confirmed in our area at this time, control time in Michigan begins mid May and runs through mid July.

The products of choice for many borers are now permethrin or bifenthrin. Imidacloprid is fairly new on the market, and one trade name is Merit (sold for homeowners as Bayer Advanced Garden Tree and Shrub Insect Care). This product use rate is an ounce per inch of circumference of the tree trunk. You then mix it with three gallons of water and pour around the base of the tree. It may take a few months for it to translocate though the tree. A good time to apply it is in early spring when the sap rises. These treatments need to be completed by late May to have a chance of getting the current season borers. Each treatment lasts about a year, and is more successful on younger trees. Fruit trees generally are treated differently, with Sevin or bifenthrin applied to the trunk, or just using the regular spray program due to the possibility of residue in fruit

Zimmerman pine moth is one of those "kind of borers." It generally affects only severely weakened trees, and goes just under the bark to girdle the cambium layer. It seems like older Scotch, red, and Austrian pines are favorites when they begin to decline. Permethrin is recommended for Zimmerman pine moth. Bird damage from yellow-bellied sapsuckers on trunks and main limbs also looks like borer damage to many. This bird damage is easily recognized by the evenly spaced holes in a straight line.

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