ASK THE HORT AGENT
Question When should we keep an eye out for pecan weevils?
Answer Now is the time to begin the weevil watch. You may want to organize a neighborhood weevil watch. It would be like a neighborhood crime watch, but more focused on the ground.
The pecan weevil does more damage to pecan nuts than any other insect. Ironically, most folks don’t even realize a weevil is doing the damage. The average person sees the immature weevil eating the pecan, and asks “what are these worms in my pecans?”
From mid-August until the end of September, pecan weevils emerge from the soil beneath the pecan trees. Since they are underground, they rely on the rain to loosen the soil so they can dig out. It usually takes at least a half inch rain shower to trigger their release.
Adult weevils then cause two types of damage. Some pecans drop from the trees when the adult weevils puncture them. These pecans are immature and can not be salvaged. Other pecans remain on the trees while the adult weevils lay eggs in the nuts. The eggs hatch and the baby weevils (larva) feed on the nuts. When the pecans falls to the ground all that remains is hollow nuts with fat baby weevils (worms) inside.
The worms will exit the pecan shells and dig into the ground to start the process all over again. Pecan weevils are extremely hard to kill when they are underground. Therefore, they need to be targeted when they emerge in August and September.
Simply spray the ground under the pecan trees (wherever the nuts fall) a day after each weekly rain shower. The safest and easiest thing to use is liquid Sevin (carbaryl). Other contact insecticides, like Bayer’s Multi-Insect Killer, will also work. If it doesn't rain for a week, then wait until it does. You may want to also spray the trunk of the pecan tree. Approximately 25% of the weevils walk up the trunk to the pecans. The other 75% of the weevils fly to the treetops. While ground sprays will reduce the damage, you may still find a few pecans with a hole and no nut inside. Some weevils may fly in from a neighboring tree. Nothing is going to be 100%.
Now get out there on guard duty. All grey weevils should be either captured or killed on site. It is a ruthless job, but your nuts are at stake. For more info visit http://www.ces.ncsu.edu/depts/hort/hil/ag81.html If you don’t have internet access, then call the Extension Office at 893-7533 or email me at firstname.lastname@example.org
Weevils used to be called snout beetles, because they appear to have a long elephant-like nose. It is now politically incorrect to reference a weevil by his body part. It is also anatomically incorrect since this snout-like appendage is actually his mouth not his nose.
Gary L. Pierce
Horticulture Extension AgentHarnett County