Weevil time

County Agent’s Corner

Tanglefoot applied to the trunk of a pecan tree. -Ralph Ballew | Snead

Tanglefoot applied to the trunk of a pecan tree. -Ralph Ballew | Snead

We are definitely in the dog days of summer! Some folks have had adequate rainfall while others could still use a shower or two. Water is critical at this time of year if you want to produce a good pecan crop. Individuals have reported pecans dropping off the trees. This could be due to a heavy crop load and lack of enough water to support the crop or it could be due to a disease called scab. Hopefully, you will have enough nuts remain on the tree to make a few pies at Thanksgiving and Christmas.

Every year I receive calls from folks with holes in their pecans. These holes, about the size of a pencil lead, are caused by the pecan weevil. I have written about this insect before but want to remind everyone that NOW is the time to address this problem.

The pecan weevil, which looks much like a boll weevil, emerges from the soil (where it has lived for the past two to three years) from mid-August through mid-September. The emergence of adult weevils is directly related to soil type and moisture conditions. They will be slower to emerge from clay soils, but only by a week or two. Drought stress may also delay emergence.

They proceed to the tree in different ways. About 77 percent of the weevils will fly to the tree trunk at a height of six to eight feet, 5 percent will walk to the trunk, and about 15 percent will fly directly to the canopy of the tree.

Once in the canopy they lay eggs in the young pecans. The eggs hatch and the larvae eats the kernel as it matures. When the larvae is ready to pupate, it drills a hole in the mature nut and falls back to the ground to repeat its life cycle.

You won’t notice any of this until you begin to pick up your pecans later in the season. You may actually find some weevil larvae in those early pecans that you harvest.

We want to target these insects with insecticides as they emerge. Granular insecticides may be applied under the drip line of the tree. Be sure to check the label to see if a rainfall event is needed to activate the release of the chemical. You may also apply liquid insecticides to the area under the trees on a weekly basis; again, just check the label to see how long the insecticide is active. Don’t forget to spray the trunk of the tree as well.

There is a sticky substance called tanglefoot that will capture the insects as they walk up the trunk. Some folks will put a piece of cardboard or duct tape around the trunk and put the tanglefoot on the tape and not directly on the tree. Just remember to get it up around six to eight feet off the ground.

Knowing that these insects can survive in the ground for up to three years will require an effort to control for multiple years. Once and done will not get rid of the weevil long term.

That being said, some folks don’t have a problem with the weevil at all, while others have a problem; some years more than others. Remember, environmental conditions play a big role in the emergence of these weevils.

If you have a few peach trees in the back yard, your chores are not finished. Mid- to late-August, after the peach harvest is over, is the time to apply a borer spray to the scaffold limbs of your peach trees. Target the lower scaffolds and trunk to prevent this insect from attacking your trees.

The last week of August is the perfect time to set out transplants of cole crops such as broccoli, cabbage, collards, and cauliflower. Planting at this time will insure your harvest will be right around the Thanksgiving holiday. You can’t beat fresh vegetables from the garden at Thanksgiving!

These crops grow much better in the fall than they do in the spring. Just remember that you are setting out a salad during the peak of insect season, so be prepared to protect them with insecticides. Scout often to make sure insects are under control. Crickets, grasshoppers, loopers, imported cabbage worm, harlequin bug, and yellow margined leaf beetles are just a few to keep an eye out for.

This is the last call for anyone wanting to take the Master Gardener class this fall. It will not be offered again in Blount County until fall of 2021. Call me if you have questions.

Dan Porch is County Extension Coordinator with the Blount County Extension Office. Dan lives in and loves Blount County and is available to answer your questions about conservation, agriculture, natural resources, and gardening. He can be reached at (205) 274-2129 or porchdw@aces.edu.