Berry’s Picks

Late Season Pecan Pest

Pecan weevils are a major pest for both commercial pecan production and backyard pecan producers in Comanche and surrounding counties.

Under normal soil conditions we could expect to see 80% of adult weevils emerge between August 20 and September 10th. With the amazing August rainfall we have received, we can expect to see weevil emergence early.

In fact, weevils were caught in some native orchards last week.

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 help 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. Sorry, I am a little late with this information, but if you have not started you weevil sprays, I would still do so.

Pecan aphids are another late season pest that can require treatment.

They are responsible for all the honey dew that covers your vehicle when parking under pecan tree.

There are both yellow and black aphids, of the two black aphids are the most economically damaging, but at high enough levels yellow aphids can also be economically damaging.

For yellow aphids the threshold level is an average of approximately 25 per compound leaf. For black aphids the threshold is 3 per compound leaf.

The recent rain events will help to control yellow aphids but may not do much for the more damaging black aphids.

Black Aphids are called black aphids because at the adult stage they will be very dark green or black and unlike the yellow aphid the black aphid can often be found on the top of the leaves.

Another issue is that treatments for pecan weevil can cause aphid flare ups due to the elimination of beneficials.

In that case it may be necessary to treat for aphids or combine an aphid treatment with your weevil treatment.

There are many treatment options available for aphids, but due to resistance issues make very effort to rotate between various Modes of Action (MOA) in your pesticide selections.

For homeowner’s aphid control options are limited but using a soil drench of imidachloprid is still a good option. A product like Bayer Advanced Tree & Shrub Insect Concentrate will be your best option, but as the product is a systemic, you really need to apply it in the spring or early summer to control aphids in the fall.

We do have an excellent pecan and fruit tree spray guide available for homeowners at the office.