Pecan weevils are a major pest for both commercial pecan production and backyard pecan producers in Comanche and surrounding counties. Soil type and soil moisture conditions dictate the emergence of adult weevils as much as anything. Hard soil will delay emergence of the weevil. Under normal conditions we would expect to see some pecan weevils starting to emerge in early August. Under normal soil conditions we could expect to see 80% of adult weevils emerge between August 20 and September 10th. However, under dry hard soil conditions, the weevils will not emerge until we have a rain event or irrigation to soften the soil. Orchards with drip irrigation can expect normal emergence near the emitters, but later emergence in the dry areas of the canopy not reached by the drip irrigation.
The adult pecan weevil is a brownish weevil about 3/8 inch long. The female’s snout is as long as its body; the male’s snout is somewhat shorter. The larvae are cream colored grubs with reddish heads. When fully grown, larvae reach a length of 3/5 inch. Their presence can be determined by finding legless grubs in pecans during September and October, or nuts at harvest with one (rarely two) small round hole(s) in the shell. Infested pecans can be detected by finding larvae where pecans are being stored or on cleaning tables.
Traps are often used to determine if adults are in the orchard, and to monitor their emergence. Adult weevils damage pecans by feeding and/or laying eggs in the nuts. Damage can occur from the time that weevils emerge from the ground until shuck split, but the goal should be to prevent egg lay from taking place. At least two spray applications, and maybe more, will be required to control the weevil. Typically, the first spray will be August 20 or 22nd, which usually coincides with when the earliest maturing nuts of the early varieties are in the gel stage at the distal end of the nut. A second application will be needed 10 days later. Commercial pecan orchards that have a history of pecan weevil must be treated to control the weevil. If you are a homeowner you will have to decide if you want to try and control the weevil or have a percentage of your crop damaged from weevils.
If you are a homeowner and have a history of weevil damage you can control the weevil by spraying Carbaryl commonly known as Sevin on the pecan trunk. Start on August 20 and spray trunks every 7 to 10 days covering a band 2 feet or more all the way around the trunk. Follow label directions. For more information on the pecan weevil you can come by and pickup a copy of “Controlling the Pecan Weevil.”