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Cotton plants can be damaged by a wide range of insect pests throughout the growing season. Symptoms include curled leaves, chlorosis, misshapen flowers, aborted squares and bolls, and damaged bolls, including stained lint. It is imperative for cotton to be scouted regularly and thoroughly. Inadequate scouting can lead to increased insect populations and decreased yield potential.
Weed control. Removing weeds from the field helps limit available plant material that can harbor insects.
Insecticide application. Insect pressure varies by year and by field; therefore, insecticide application should be based on scouting observations, and not by a pre-determined schedule. Apply during the most susceptible stage of insect development and be mindful of preventing resistance.
Plant growth regulator (PGR) application. Controlling plant height with PGRs can help prevent rank growth that can reduce insecticide coverage and extend the time for ground application before an aerial application would be necessary.
Scouting. Effective cotton insect control relies on frequent and thorough scouting. Fields should be scouted every 4 to 5 days with enough time spent in the field to accurately assess insect populations and stages. The objective is to avoid unnecessary insecticide applications and time applications correctly. Allot time for additional field checks to account for possible increased insect pressure.
Beneficial agents. Lady beetles, spiders, minute spider bugs, parasitic wasps, and insect fungal diseases help control inspect pests. It is important to identify these beneficials correctly in the field and what they help control to help prevent unnecessary insecticide application.
Economic thresholds. Economic thresholds are the point at which insect density requires action to prevent economic loss. It is important to apply insecticides based on scouting and threshold levels to reduce costs and loss of beneficial insects. Thresholds can vary for several reasons including insect species, crop development stage, yield potential, treatment cost, market price, secondary pests, and other considerations. Use local thresholds recommended by state extension specialists along with on-farm considerations.
When late-season insect economic threshold levels are met, first consider what cotton technology the crop contains. Fields that are planted with technology that manages certain insect pests may still require insecticide application in fields with heavy insect pressure. Be sure insect pests are at threshold prior to treatment. Insect control should be terminated at 350-400 DD60s after “cutout” or at 5 nodes above white flower (NAWF). Cotton fields do not need treatment beyond this stage as the crop is less attractive to insect pests and the bolls can tolerate more damage without reducing cotton yield potential.
Figure 2. Tarnished plant bug adult.
Figure 3. Brown stink bug adult.
Figure 4. Aphid infestation present on the underside of a cotton leaf.
Figure 5. Cotton bollworm. Peggy Greb, USDA Agricultural Research Service, Bugwood.org.
Figure 6. Fall armyworm.