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Pecan Weevil Time Soon!

posted Jul 25, 2011, 9:04 AM by Bob Whitney   [ updated Jul 25, 2011, 9:17 AM ]
It seems like such a very short time ago that we were dealing with pecan weevil problems and here we are again. Pecan producers are always concerned about pecan nut casebearer and rightfully so but for those producers that have pecan weevil problems in their orchard no other insect is as destructive.
The pecan weevil lives in the ground for at least two years before it emerges as an adult. The adult can fly but prefers to walk up the tree from the ground and begins finding nuts. The weevil has a long snout that it uses to puncture the pecan and either feed or lay an egg in the hole. This egg hatches out and the grub or larva feeds inside the nut before boring a hole in the shell and dropping to the ground. The hole you see in so many pecans is the result of the weevil leaving the pecan. The female weevil can feed in a pecan in the water stage but she cannot lay an egg in the pecan until the nut has the gel like substance inside. We are currently going from the water stage to the gel stage in many pecans. 
Several things have to be together in order for the weevil to be a problem. First the soil has to be loose enough for the adult pecan weevil to leave the ground. We have had nothing but drought so soils are hard but weevils can emerge through ground cracks. Second be sure and check the pecans to make sure they are in the right stage of development. If the ground is loose or cracked and the pecans are right then lastly make sure you have the pecan weevil. Put out a white cloth under some limbs and then shake the limbs to knock out the weevils. Look for them on the sheet, if you find some then it is time to spray.
There are many sprays for pecan weevil but unfortunately there are no organic sprays. To minimize insecticide use small growers may want to try a trunk spray. Carbaryl commonly known as Sevin is an excellent material since it has a very low toxicity and is easily found. Since most yard trees are very big it is really easier for a homeowner to apply Sevin to the trunk instead of the entire tree. Soak the trunk from the ground to breast high and the weevils will walk up the tree and of course contact the poison. The largest portion of weevils do walk up the trunk so this makes for an easy homeowner or small orchard treatment that is generally quite effective.
Pecan Weevil Facts You May Not Know
The pecan weevil is one of the most destructive pests of pecans. Most people have more problems with it simply because this insect infests nuts we have already taken through the season. There is nothing worse than spending money on a pecan and then seeing an insect eat it and we are right at the time for pecan weevil to be a problem. 
Here are just a few facts about pecan weevil you may not know. The death rate in a 2 year cycle for weevil is 66.9-96 percent and for 3 years is 99.6 percent. We lose a lot of pecan weevils before they ever get out of the ground! Males feed on an average of 0.29 nuts per day while females feed on 0.23 nuts per day. We always worry about the number of pecans damaged from feeding but that is very small compared to egg lay in the pecan. Males live on average 21 days while females live 23.8 days. It takes 5 days from ground emergence for a female to start laying eggs. Females lay eggs in an average of 22.7 nuts per female. It doesn’t take too many weevils to mean a lot of damage. For many commercial growers even one weevil is too many. These early emerging weevils can be costly but the late weevils can end up in a sack of saleable pecans which is a real problem.
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