Insect Management in Cotton Insect Management in Cotton
Insect Management in Cotton1
Richard K. Sprenkel 2Effective and economical cotton insect control involves the integration of many control techniques. These techniques include using beneficial insects and diseases and cultural control practices to the fullest extent possible. Chemical insecticides are still the most important suppression tool, but they should be used selectively and at the proper rate and time.
Thresholds
Beet Armyworm: Treat when 2 or more hatching egg masses ("hits") per 100 row feet are found.Bollworms, Tobacco Budworms: In previously untreated fields, apply a recommended insecticide when an average of 10 small larvae per 100 plants or 30 eggs per 100 plants are present. In previously treated fields, when benificials are absent, apply a recommended insecticide when an average of 5 small larvae or 25-30 eggs per 100 plants are present. For Bt transgenic cultivars, an application of a recommended insecticide is justified when an average of 8-9 larvae at least 1/4 inch in length per 100 plants are present. Several larvicides also have ovicidal activity. These insecticides include Baythroid, Curacron, Karate, Lannate, and Larvin.
Cutworms: Control when worms are found destroying a stand. Cover plants and surface of ground along rows with insecticide.
Fall Armyworms: Treat when 15 to 20 or more small larvae per 100 plants are found.
Loopers: Economic damage seldom occurs; however, if chemical control is necessary, loopers should be controlled when they are small. A population of 4 or more loopers per foot of row justifies treatment.
Other Pests
Cotton Aphids: If necessary, apply controls when leaves appear sticky and heavy infestation develops. Repeat applications may be necessary for chemical control. Generally, chemical controls are not necessary because of the actions of parasites, predators, and disease.Fleahoppers, Plant Bugs: Make 1 or more applications when 1 adult or nymph is found per row foot before bloom. If pinhead square set is less than 80%, treat when 1 adult or nymph is found per 2 row feet. After first bloom, cotton that is not squaring normally should be treated if 30 or more are found per 100 terminals. If a sweep net is used, treat when there are an average of 7.5 or more plant bugs per 100 sweeps. NOTE: If Admire is used at planting or side dress for other insects, it should have a period of lasting control against plant bugs.
Spider Mites: Treat around field edges when mites first appear, this may prevent heavy infestation later. Treat entire field when leaves begin to redden and medium infestation occurs. Two or more applications at 5 to 7 day intervals may be needed.
Stink Bugs: Control is justified when there are 4 or more stink bugs per 100 sweeps or 1 stink bug per 6 feet of row.
Thrips: Apply spray when 2 or more thrips per plant are present when cotton comes to a stand. Repeat treatment in 7-10 days if needed.
Whiteflies: For active growing cotton, treat when 50% or more of the plant terminals have clusters of whiteflies on them. Two or three applications at 5-day intervals are usually needed to bring an infestation under control.
For mature or stressed cotton, make 2 applications 5 days apart when honeydew is accumulating and sooty mold appears on leaves.
Pyrethroid Resistance Management
In 1987, a pyrethroid-resistant population of tobacco budworms was documented in Brazos County, Texas. Since then, resistant tobacco budworms have been identified in several other states including Florida. Because of field control failures and an increase in the levels of resistance, most states have implemented a Pyrethroid Resistance Management Plan. The following management plan should be followed for non-Bt cotton in Florida.
1. Manage crop for earliness
2. From planting to first bloom:
- Do not use pyrethroids.
- Scout cotton and treat only on an as-needed basis.
3. From first bloom through the following 6 weeks:
- Scout cotton twice weekly.
- Treat on basis of bollworm/budworm eggs and small larvae.
- Use pyrethroid at mid-range rates in combination with Bacillus thuringiensis (B.t.) or non-pyrethroid ovicide.
- If control of a tobacco budworm generation using a pyrethroid plus B.t. or an ovicide is not satisfactory, use larvicidal rates of a carbamate or organophosphate insecticide for the next treatment of that generation.
4. During late season:
- Do not use pyrethroids.
- Use larvicidal rates of an organophosphate or carbamate for tobacco budworm control if treatment is justified.
- Terminate all insecticides as soon as possible.
Pesticide Restrictions