Cotton Pest Management Newsletter #10
August 8, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending August 4^th listed the crop as 95 percent setting bolls and 9 percent with open bolls. Crop conditions are highly variable due primarily to available moisture. We would expect to see some early planted dryland fields defoliated soon.

Insect Situation: Tobacco budworm and corn earworm continue to be the primary insects of concern. Sporadic infestations of various armyworms (beets, falls, and southerns) have been reported. Soybean loopers have also been observed in various locations. Bug injury is variable depending on location in the state.

Tobacco Budworm and Corn Earworm: Many areas of the state continue to observe sustained infestations of tobacco budworm (TBW) and corn earworm (CEW). In central and southwest Georgia, TBW appears to be the predominant species. Egg lay has been high, multiple eggs per plant, in some areas. We would expect activity to be most intense on lush green fields at this time compared with cotton which has cuttout or is extremely drought stressed. In areas where TBW has historically infested cotton, infestations should be treated as a TBW infestation. A non-pyrethroid insecticide is recommended for control of TBW. Insecticide applications must be applied on a timely basis, targeting larvae less than 1/4 inch in length, to achieve optimal control.

Bt Cotton: Bt cotton has provided excellent control of TBW and good control of CEW. However some fields have required treatment for escaped CEW. We are still seeing CEW moths in fields and scouts should continue monitoring Bt fields closely, especially the area of the plant just below the uppermost white bloom. Treatment for CEW in Bt cotton should be based on larvae that are approaching 1/4 inch in length. Pyrethroids have provided very good control of CEW. Scouts should also be observant for armyworm species in Bt cotton. Although sporadic, treatable infestations of fall, beet, and southern armyworms have been reported in Bt fields. Soybean loopers may also potentially be an economic pests in Bt cotton.

Fall Armyworm: During recent weeks, we have observed low numbers of fall armyworms (FAW) infesting cotton. Recently, treatable infestations were reported from isolated fields in southwest and southeast Georgia. FAW can be very difficult to control, especially when they have sized. If detected early, 1/8 inch in length, pyrethroids will provide good suppression. Early infestations of FAW can be difficult to find. Be sure to examine white and red blooms for small larvae and also be observant for bract etching. Small FAW will often etch the inner surface of developing bolls prior to penetrating the boll. If etching or small areas of "windowpaining" are observed on boll bracts, be sure to open bracts and look closely for a small FAW. Although small FAW and CEW/TBW appear nearly identical, the presence of etching would suggest a FAW infestation. Treatment is suggested when 10-20 small larvae are found per 100 plants. Control of large larvae, greater than ½ inch in length, is difficult.

Southern Armyworm: We have had a few calls concerning southern armyworm (SAW). Most often, infestations of SAW are observed in fields which have not been treated for larval pests, or not treated during recent weeks. In some fields, localized infestations will be observed and a small portion of the field may be defoliated. If these areas are detected, spot treatment may be possible. However, we may also observe uniform infestations in some fields. Decision to treat should be based on defoliation and fruit feeding. SAW have historically been very susceptible to insecticides used to control other caterpillars.

Soybean Looper: Soybean looper (SBL) larvae have been observed in low numbers in various areas. SBL will initially feed on foliage low in the plant canopy and in time will move up the plant.

Bugs: Scouts should continue monitoring for boll feeding bugs. Stink bugs, plant bugs, and leaf-footed bugs are all capable of damaging developing bolls. The internal feeding injury on the inner surface of the boll wall appears similar for each. When monitoring medium sized bolls for internal injury, be aware of the boll population which is still susceptible to feeding injury. If you have to hunt for bolls small enough to examine internally for damage, it is likely that you will observe an inflated count since the bugs are concentrating their feeding on a smaller percentage of total bolls in the field.

Insect Updates: Check the Cotton Insect Hotline (1/800-851-2847) for updates on current insect conditions. The Cotton Pest Management Newsletter is also posted on the Internet at "www.gaipm.org" and then click on "cotton".

Sincerely,

Phillip Roberts
Extension Entomologist