Cotton Pest Management Newsletter #7
July 18, 2002

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending July 14^th listed the crop as 95 percent squaring and 64 percent setting bolls. Crop conditions were generally listed fair to good, but some areas remain dry. Early planted dryland fields have cut out in dry areas. A few fields with open bolls have been reported.

Insect Situation: Tobacco budworm and corn earworm are the primary insects of concern at this time. Pressure has generally been moderate but sustained. Although we have had difficulty controlling tobacco budworm with pyrethroids, we do not need to panic. With thorough scouting and good decision making (insecticide selection and timing of applications) these populations can be effectively managed. Armyworms, both falls and beets, continue to be reported in some areas. Treatments for boll feeding bugs have been initiated in some areas.

Tobacco Budworm and Corn Earworm (Non-Bt Cotton): Proper insecticide selection and timing of spray applications are critical for management of tobacco budworm (TBW) and corn earworm (CEW). If economic populations of TBW are infesting a field, either Tracer or Steward should be used. These products must be used in a timely manner, targeting larvae less than 1/4 inch in length. Tobacco budworms greater than ½ inch in length (5 days of age) are very difficult to control. The age and approximate size of TBW/CEW larvae are listed in the table below.

Pyrethroids remain a good option when CEW is the primary species targeted. When mixed populations occur (TBW and CEW), the infestation should be treated as a TBW infestation, especially if a threshold level of TBW alone is present. In fields where sustained pressure occurs, multiple applications on a 4-5 day interval may be needed.

Bt Cotton: We have received a few reports of Bt cotton requiring supplemental treatment for CEW. Bt cotton has provided excellent control of TBW. Scouts should be monitoring at least one bloom, one bloom-tagged boll, and an additional boll in addition to the upper 12 inches of the plant for eggs and larvae in both Bt cotton and non-Bt cotton. During previous years, when CEW escapes have occurred in Bt cotton, the majority of CEW larvae have been near the uppermost first position flower and the next few nodes below the uppermost flower. Be sure to look in blooms and under dried blooms, often escaped larvae will penetrate the tips of bolls which are covered by the drying flower. Pyrethroids are a good choice for treatment of CEW in Bt cotton. In addition to controlling CEW, pyrethroids will provide good control of southern green stink bugs and plant bugs which may also be infesting the field as well as suppressing small fall armyworms.

Fall Armyworm: Fall armyworms have been reported from isolated areas. Most larvae reported this week are small and counts have been low to moderate.

Boll Feeding Bugs: Scouts should be monitoring medium sized bolls (about the diameter of a quarter) for symptoms of feeding injury. In addition to stink bugs, plant bugs and leaf-footed bugs may also feed on developing bolls. In fields where threshold levels of feeding are observed (20% internal damage), scouts must make observations on which bugs are likely causing the damage. Such observations will affect insecticide selection.

Brown Stink Bug: As a whole, stink bugs have been much more visible in cotton this year compared with recent years. In fields where we have visited, a mix of southern green and brown stink bugs has been observed. In fields where high populations of brown stink bugs are observed and internal boll damage exceeds the 20% threshold, an organophosphate insecticide should be used.

Southern Armyworm: We have received a few reports of southern armyworm (SAW) this week. Most infestations have been reported in fields which have not been treated with a larval insecticide to date. SAW are grayish to nearly black in color with an orangish head capsule. Eggs are laid in masses similar to beet armyworm, but the egg cluster is much larger. Hatching larvae will feed similar to beets. SAW larvae can often be recognized by the appearance of several large black dots on the first abdominal segment behind the third pair of true legs, almost appearing as a black band around the body. Southern armyworm have historically been very susceptible to insecticides used for other caterpillar pests.

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