Cotton Pest Management Newsletter #12
August 16, 2001

Cotton Situation: The Georgia Weekly Weather and Crops Report for the week ending August 12^th listed the crop as 94 percent setting bolls and 4% with open bolls. The crop remains in fair to good condition but some areas are severely drought stressed.

Insect Situation: Tobacco budworm and corn earworm activity increased during the past week in many parts of the state. Bug damage also continues to be reported on developing bolls. A few isolated reports of spider mites have been received. Silverleaf whiteflies have been observed in some fields in the Tifton area.

Tobacco Budworm and Corn Earworm: Both tobacco budworm (TBW) and corn earworm (CEW) numbers increased during the past week. We have received reports of large larvae appearing when eggs and small larvae were not found in previous scouting visits. Most likely eggs were laid low in the canopy and overlooked during the previous field visit. Scouts need to be sure and monitor plants closely. Eggs and small larvae may be found throughout the plant. During a recent agent training held in Tifton, the majority of eggs found were on bracts and blooms. One and two day old larvae were also being found in white and pink blooms in both Bt and non-Bt cotton. Although a small percentage of Bt cotton has required supplemental treatment for control of CEW, we must stay vigilant in our scouting process. When escaped CEW are found in Bt cotton, they are most often associated with blooms and bloom tagged bolls. Treatment of CEW in Bt cotton is recommended when 7-8 larvae 1/4 inch in length are found per 100 plants. We would anticipate mixed populations of TBW and CEW for the remainder of the season. Counting moths while walking fields should give us an idea of which is the primary species and allow growers to make better decisions when selecting insecticides. A large percentage of cotton acreage remains attractive and susceptible to bollworm injury.

Fall Armyworm: Low numbers of fall armyworm have been observed in isolated areas. Fall armyworm is a difficult insect to control with insecticide and early detection is the key. Small fall armyworms are most often found in white and red blooms or feeding on the inner surface of boll bracts low in the plant canopy.

Stink Bugs: Be sure scouts are monitoring for stink bugs.

Silverleaf Whitefly: Silverleaf whitefly (SLWF) has been a serious pest of late planted cotton in some areas during recent years. The most severe infestations have occurred in Tift, Colquitt, and surrounding counties. Low numbers of SLWF adults have been observed in cotton for several weeks. Numbers have generally been low but appear to have increased recently. I have not observed a field which would require treatment but scouts should report the presence of SLWF adults if observed in the field. SLWF appears to thrive during dry periods and numbers can build rapidly. In fields where adults are observed, effort should be made to conserve beneficial insects. Several predators and parasitic wasps attack SLWF and their removal may cause SLWF numbers to flare. If a field must be treated for another pest, use selective insecticides where possible. Tracer or Steward would be options for controlling TBW or CEW. If stink bugs are the target, Capture or Leverage would be options. These treatments will reduce beneficials but will also provide some suppression of SLWF. We will continue to monitor the development of SLWF. Please let us know if numbers are building in your area, especially if immatures are observed.

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