If you live in Robeson County, you are well aware that we have to deal with insect pests all year long. As the seasons change, so does the kind of insect we have to deal with. We might have to fight the battle with fire ants throughout the year, but certain pests, like Japanese beetles, azalea caterpillars, carpenter bees, and bagworms, are a nuisance only some of the time.

If you have pecan or peach trees, there are a couple of insects you need to pay special attention to. This is the best time of the year to control peach tree borers and pecan weevils.

Peachtree borers are caterpillars that bore into the lower trunk of peach, plum, and cherry trees. When in the moth stage, this insect is most active and lays the most eggs between August 15 and September 15.

The moths lay eggs at the base of the trees. From these eggs hatch tiny, white caterpillars that bore into the bark and tunnel in the cambium at the base of the tree. A gummy substance can often be seen oozing from the tree where the borers entered the trunk. If a lot of borers infest a tree, the cambium may be completely girdled beneath the bark, and the tree will eventually die. The borers pupate inside the infested tree during late spring, emerges as a moth a few weeks later, and the cycle starts all over again.

Since the moths will be laying eggs at this time of the year, this is when chemical pesticide treatments will be most effective. It does not do any good to spray at other times of the year, because the moths are not present, and the borers are deep into the trunk of the tree where the pesticides cannot penetrate. The only way to kill the caterpillars once they are in the tree is try to gouge them out from under the bark with a piece of wire. This is very tedious and time-consuming work and is usually not very effective.

For homeowners, the most effective treatment for peach tree borers is to drench the lower trunk and the soil around the base of the tree with insecticide products containing esfenvalerate, permethrin, cyfluthrin, or other pyrethroids. The first treatment should be made around the third week of August and then repeated two to three weeks later.

Mix the insecticide in a bucket of water and pour the mixture on the tree trunk about three feet above the ground. Let the mixture soak into the ground at the base of the trunk. It is not necessary to treat higher into the tree, since the moths lay eggs only at the base of the tree.

In eastern North Carolina, pecan weevils begin emerging from the soil in August. This is the most serious late-season pest of pecan and hickory.

Adult pecan weevils are reddish brown to gray beetles with long snouts. Like other beetles, these weevils go through four distinct stages of development: egg, larval, pupal, and adult. The eggs are white and are laid inside the pecan nuts. These eggs then hatch out into a little white grub that feeds and develops inside the nut. The larva then cuts a small hole in the nut so it can get out. It then goes into the ground where it spends the winter in the pupal stage. Finally, the pupal stage develops into an adult that emerges from the ground about this time of the year, and the cycle starts all over again.

Adult pecan weevils are very poor flyers, so they usually crawl up the trunk of the tree instead of flying. They cause damage by puncturing nuts as they feed. This puncturing often causes the nuts to drop from the tree. Eggs are also laid in the nuts and the larvae that hatch then feed on the nut. When the larvae mature, they chew an exit hole in the nut and then go into the ground.

Pecan weevil adults usually begin emerging in August, after a heavy rain of one inch or more, and continue emerging through September. Foliar insecticide sprays directed into the canopy of the trees at this time of the year is the most effective way to control these insects. This requires the use of aerial applicators or commercial spraying equipment, which is not very practical for homeowners who have only a few trees around the house.

Now that you know the life cycle of pecan weevils, let me suggest what you can do to reduce the amount of losses for this pest. Sanitation is important. Gather all nuts as they fall from the tree and either burn them or send them to the landfill with your trash before the larvae gets a chance to go into the ground. Since most adult weevils will crawl up the tree, wrap a sheet of burlap around the trunks of your pecan trees and cover it thoroughly with Sevin dust. This burlap wrap should be a few feet from the base of the tree and should be gathered loosely so most of the weevils will crawl up under the burlap. Soil applications of permethrin, cyfluthrin, or other pyrethroids can also be used to kill adult weevils as they emerge from the soil. (Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.)

If you have pecan or peach trees, now is the time to protect your investment. Do not wait until the damage is done to take action.

E-mail address: Everett_Davis@ncsu.edu

Mailing Address:
P. O. Box 2280
Lumberton, NC 28359-2280

Phone: 910-671-3276
Fax: 910-671-6278

Date Created 8/20/09