News release, August 12, 1999, effective immediately.
For media inquiries, contact Caroline Booth Lara, Communications Specialist, (580) 224-6379.
  email: cblara@noble.org

Pecan Producers: Watch for Weevils!

Early signs indicate a good pecan harvest ahead for Ardmore-area orchards, but at least one threat remains that could change the prospects for the worst - pecan weevils.

"The dry weather keeps most of them locked up in the ground," said pecan specialist Scott Landgraf, with the Noble Foundation in Ardmore, "but watch out when there is a significant rain."

"There is no way to follow what someone else is doing in their orchard; rainfall patterns will be as different as weevil populations, so watch what is going on in your orchard," Landgraf urged area pecan growers.

Although Oklahoma-grown pecans are generally known for having high-quality meats, past weevil infestations have resulted in area nut crops being so severely discounted, there was no price offered for them, Landgraf said.

Now is the time for pecan producers to act against the destructive insects. Landgraf suggests the following steps:

1) Identify the best way to apply insecticide to control weevils. If a significant problem exists, a mist blower is most often used for larger orchards, while a handgun sprayer is acceptable for smaller acreages. Aerial application is another possibility, Landgraf said, with helicopter applications slightly preferred.

2) Estimate the weevil population. One of the most effective techniques is trapping adult weevils. Research has shown circle traps* placed on tree trunks catch the most weevils. Pyramid traps are accepted as reference traps, but are vulnerable to livestock since they sit on the soil surface. Another scouting method is to spray a tree with Sevin 80S insecticide and see what falls onto a tarp placed on the ground below it. As a last resort, try shaking limbs over a pickup bed and see what falls out.

Looking at pecan nuts can indicate weevil activity. If a weevil bores a hole into a developing nut still in the liquid or gel stage, the nut will abort and fall to the ground within three days. When checking nuts on the ground, look for "tobacco stains" from fluids emerging from the puncture.

Nuts remain on the tree after reaching their solid state after being punctured by a weevil. The weevil's tracks are visible around the drill hole, often making it look like a bull's eye. Producers finding the telltale tracks may already be too late - eggs or even larvae are inside the nut.

Sevin, the pesticide of choice for weevil control, has a 10- to 14-day residual period. When that time has passed, orchard managers should begin scouting for another infestation. Often, a second insecticide application is required, and with bad infestations, even a third may be needed.

Weevils are a threat from mid-July to early October. Weevil larva pupates in the soil, where they remain for two or three years. Some soils prevent the escape of adult weevils until it is softened by rainfall. Dry periods can group weevil concentrations for more specific control opportunities.

"For best control, orchards must be scouted individually - a neighbor's information may be useless," Landgraf said.

To learn more about trapping weevils and their control, obtain the Oklahoma State University Cooperative Extension Fact Sheet F-7190, or visit the pecan production web site at http://www.dasnr.okstate.edu/pecan.

Landgraf can be contacted by calling the Foundation at (580) 223-5810.

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* - Photos available on the Noble Foundation web site at www.noble.org in the News Releases section.

(FYI — The Noble Foundation is a privately funded, nonprofit organization headquartered in Ardmore, Okla. The Foundation conducts agricultural and plant biology research; provides grants to numerous other charitable and educational organizations; and assists farmers and ranchers through educational and consultative programs.)