Watching the news and weather forecast last night showed much for the same for the next 5-7 days. Hot, dry and sunny. The hot, dry weather has caused excessive moisture loss to soil and plants across the area. Sorghum is pre-maturely maturing out and cotton in some areas has shut down and is three to four nodes above white flower. Dryland cotton in most of Runnels County is showing severe drought stress this week, especially those fields which have been blooming for the past 10-12 days. Cotton in the Miles/Rowena area is holding up well and is progressing nicely. It's amazing what a 1-3 inch rain can do for crops when it's timely. Irrigated cotton in well into bloom with an excellent fruit load and irrigation is in full swing where water is still available.

Bollworm trap catches have dropped off and egg counts range from 8-38 bollworm eggs per 100 plants. Generally, larval counts remain below threshold levels. This is probably due to a combination of hot weather and very high natural enemy populations.

Bollworm egg counts ranged from 3-38 eggs per 100 plants or 1,260 to 15,200 eggs per acre this week. Bollworm trap catches remain high in both Runnels and Tom Green
Counties. The egg-lay began 10-12 days ago and no major larva infestations have occurred to date. That certainly could change at any time.

Irrigated cotton looks good and is progressing nicely. Remember treatments for bollworms may be justified when larval counts average 5,000 or more treatable worms per acre. However if two or more key predators are found for each small worm, control measures may not be needed or a microbial insecticide may be used. Keep in mind that the actual treatment level will vary according to the ability of theindividual scout to locate small larvae, the maturity of the crop and the crop value. As crop value goes down, thresholds go up.

Cotton aphid infestations remain very low in most fields and natural enemy populations remain high. Hopefully this will continue. There are some isolated fields which have economic infestations of cotton aphids and did require an insecticide treatment. Some were treated with Provado®and some with Furadan® Generally, aphids are not a big problem at this time. Insecticidal control of aphids should be delayed until infestations levels exceed 50 aphids per leaf.

Stink bugs are moving into blooming cotton from grain sorghum fields and cotton producers are encouraged to scout closely for this pest. Remember the damage they caused several years ago? Stink bugs feed on bolls and can cause boll shed and/or seed damage and lint staining. Sometimes damaged bolls become hard-locked as well. To scout for this pest, examine 10 row feet of cotton in several different locations in the field. When there is an average of five or more stink bugs per 10 row feet, an insecticide treatment may be justified. Stink bugs often are clumped near field margins. Spot treatment provides effective control when this situation exists.

Cotton leaf perforators can be found in some fields in Runnels County. These are generally not a concern and should not be mistaken for bollworms or some other caterpillar pests. They feed on foliage only.

It is unusual to see them this time of year because they are usually associated with late season boll maturation.

They do have the ability to defoliate cotton and should not be underestimated. Bt cotton does an excellent job of control.

Description of the Pest

Problems usually occur during hot, dry conditions in the Southern Rolling Plains. Early larval instars of the cotton leaf perforator are flattened, yellow or orange caterpillars that bore into leaves and tunnel between leaf surfaces until the fourth instar. They can be distinguished from maggots of leafmining flies by looking with a hand lens for the present of a head capsule and mandibles. The fourth instar emerges from the leaf and begins skeletonizing leaves. During the molt between the fourth and fifth instar, the larva forms a thin silk shelter and curls into a horseshoe shape inside the shelter. The fourth and fifth instars are green to gray with two black spots and several smaller white spots in each segment.

Damage

Leaves damaged by cotton leaf perforators have numerous windows, i.e., holes with a transparent membrane remaining on one side. Heavily infested leaves may be reduced to a network of veins. Most damage occurs in the top third of plants. Severe defoliation may cause bolls to open prematurely, and also cause shedding of squares and small bolls.

Cultural Control
The use of Bt cotton.

Monitoring and When to Treat

Cotton can tolerate a large amount of defoliation. However, producers should check fields at least once per week to check the progression of defoliation. Most studies indicate that cotton can tolerate 25-50 percent defoliation before yield losses occur. Treatment timing is critical because sprays cannot reach leafmining instars or horseshoe-stage larve. If infestations are severe, wait until most larvae are in the horseshoe stage, then spray within 2 days to kill the fifth instars when they emerge from their shelters. Spot treat infestations that are limited to certain parts of the field.

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IPM Radio Update is up and running. The telephone number is 365-2642. This update will give producers a general insect and crop reports for the different areas in Runnels, Tom Green and Concho Counties.

Tuesday, July 24th
Westside Gin 8:30 a.m.
Mereta Co-Op 1:00 p.m.

No Turnrow meetings in Runnels County until weather conditions change.

Tom Green Budworm /Bollworm Moth Traps

Runnels Budworm /Bollworm Moth Traps

Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level, race, color, sex, religion, handicap or national origin. The information given herein is for educational purposes only. References to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.