and their control
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[May 14, 2014]
Few things strike fear in the
hearts of tree owners like the mention of borers. Borers are most
often the larvae of beetles or moths, and they do their damage where
you can’t see it. The eggs are laid on or under the bark, and the
small hatchling chews through to the part of the tree they feed on.
They spend almost their entire lives inside the tree, where they
can’t be seen or controlled.
May 24-30 has been selected as Emerald Ash
Borer Awareness Week because it coincides with the time of year
that the adult beetles will begin to emerge. These borers have
gotten a lot of press the past few years, and have made ash
trees undesirable for planting. They are metallic green, about a
half inch long, and make “D” shaped exit holes (unlike the ash
borers we have had around here for many years which make “O”
Most borers are named for their primary
target, but they also affect other species of trees and shrubs.
As an example, the flat-headed apple borer can also affect pin
oaks and about 15 other species. Many borers leave a tell-take
hole in the trunk, but some such as the ash borer are weak and
have to enter through a pruning or mechanical injury.
Here is a listing of common borers and
their control times: Common ash borers (early June and early
July), emerald ash borer (mid May through early June), 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).
You can see borer control isn’t an exact
science. Treatment times and re-applications are hopefully timed
to catch the hatching eggs on the outside of the trunk, or
discourage the adults from laying eggs. Some new research shows
that trees that are under stress give off a certain pheromone
that attracts more borers to the tree. So, keeping your trees in
good growing shape will go a long way to helping the situation.
Fertilizing with the same rate of broadcast fertilizer used for
lawns will help (apply it early May and early September), and
watering during extreme dry periods as well (with an inch of
broadcast water per week.
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Some of choice for borer control include
permethrin, bifenthrin, and acephate. Check the label for control on
your target borer. Imidacloprid is fairly new on the market. One
trade name is Merit (one example sold for homeowners is Bayer
Advanced 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. Each
treatment lasts about a year. Fruit trees generally are treated
differently with Sevin, 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. 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.
University of Illinois
Extension director for Logan, Menard and Sangamon counties]