Summary of Losses from Insect Damage and Costs of Control in Georgia - 1997

V. Cotton Insects

P. M. Roberts, G. A. Herzog, D. C. Jones, and J. R. Ruberson

The spring of 1997 was one of the coolest on record. Seedlings struggled due to poor growing conditions and thrips injury compounded the problems of getting this crop started. Plant bug problems were more common in late June and early July than in recent years. Aphids built in some areas but few fields were treated and naturally occurring fungus eventually caused populations to crash.

Throughout the state, populations of the predatory big-eyed bugs and insidious flower bugs were unusually and inexplicably low during much of the season, which may have contributed to the increased problems with worms in many areas. Later in the season, predator populations increased, but were still well below typical levels of abundance.

Tobacco budworm pressure was light in June, but intensified in July and August. Tobacco budworm infestations were difficult to control, due in part to heavy pressure, especially in southwest Georgia. Several field collections were made and screened for susceptibility to pyrethroids by Dr. Gary Herzog. High levels of pyrethroid resistance were documented in a Decatur County tobacco budworm collection. Bt cotton performed well against tobacco budworm. Corn earworm appeared in mid-July and infestations were moderate to high depending on location. Supplemental insecticide sprays were needed on Bt cotton to control corn earworm in some areas. Fall armyworm were observed at detectable levels in most of the Coastal Plain of Georgia. Fall armyworm infestations were high during late July and August in the southern and eastern parts of the state. Control of fall armyworm was difficult and erratic with all available insecticides. Beet armyworm required treatment in some localized areas.

Stink bug populations were high in some fields during August, especially those which had not been treated with a broad spectrum insecticide recently. Boll injury from stink bugs was first observed in late July and continued to increase as the season progressed. Damage became more apparent as harvest neared and bolls began to open. Soybean loopers and whiteflies were also sporadic pests. High populations of silverleaf whitefly were observed in a localized area. Southern armyworm infestations were common during August and some fruit feeding was observed, but treatment of southern armyworm was not needed. A single cotton leafworm was also collected in southwest Georgia.

Boll weevils were detected in three counties during September. Counties included Jenkins, Grady, and Lowndes. Reproduction was occurring at the Lowndes county site. Boll weevil eradication personnel reacted promptly by intensifying trapping efforts and treating with insecticide where needed.

Late summer and fall weather was not conducive for cotton production. Lack of moisture in August and excessive rains in September and October lowered yields and quality of the crop. A below average crop of 638 lbs. lint/acre was harvested from 1,430,000 acres.

Estimates of Losses and Control Costs

¹Average price received, $0.702/lb. lint (Georgia Farm Report, Volume 98 - Number 05, Georgia Agricultural Statistics Service, February 23, 1998).
²Bt transgenic cotton costs: $32.00/A technology fee plus AI/A seed premium on 550,000 acres. Seventy-five percent of total costs charged to tobacco budworm ($13,612,000) and 25 percent to bollworm ($4,537,000).
³Grower costs of Boll Weevil Eradication Program.

Information Pertaining to Control of Major Cotton Insect Pests in Georgia in 1997

¹Includes application costs.
²Yield units measured in pounds of lint.
³Does not include costs of Bt transgenic cotton; foliar insecticides only.
⁴Grower costs of Boll Weevil Eradication Program (BWEP). All cotton produced in Georgia is required to participate in BWEP. The annual per acre assessment for participation was $5.00 per acre during 1997. One minor outbreak of boll weevils occurred in Grady County and was brought under control. Two boll weevils were also trapped in Jenkins County. Lowndes County had one 38 acre field with a major infestation and reproduction of boll weevils.