Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/1/2003
Publication Date: 7/1/2003
Citation: Snodgrass, G.L., Scott, W.P., Robbins, J.T., Hardee, D.D. 2003. Suppression of tarnished plant bugs in cotton by treatment of early season wild host plants with herbicides in nine-square-mile areas of the mississippi delta. National Cotton Council Beltwide Cotton Conference. Interpretive Summary: Non-insecticidal control measures are needed for tarnished plant bugs in cotton grown in the Midsouth. These pests are becoming harder to control with insecticides because of resistance, and insecticides are the only control method currently used in cotton. One possible control method is by reducing early season buildups of plant bugs on broadleaf wild host plants. These wild hosts are found mainly in marginal areas around roads, fields, and ditches, and occupy a small area of the total land in the Delta. Treatment of such areas with herbicides to destroy these weeds in early season could be economical because of the small area involved. This control method was tested on a large scale in 1999, 2000, and 2001 by treating all marginal areas with weeds in March or April in nine-square-mile areas of the Mississippi Delta with a herbicide which destroyed the weeds. During June and July of all three years cotton growing in the treated areas and cotton growing in nine-square-mile untreated areas was sampled for plant bugs. Cotton growing in the treated areas had about 50% fewer plant bugs per sample than were found in samples from cotton grown in untreated areas. Cotton growers in the treated area spent less money per acre to control plant bugs each year than did growers in the untreated areas. The herbicide treatment was effective in reducing numbers of plant bugs in cotton, but it did not reduce them enough in any year to a level where additional control with insecticides was not needed.
Technical Abstract: Broadleaf weeds found in marginal areas by fields, roads, and ditches were controlled with the herbicides Trimec® or Strike 3 in nine-square-mile areas of the Mississippi Delta in March or April of 1999, 2000, and 2001. These weeds serve as early season food and reproductive hosts for tarnished plant bugs and population buildups occur on these weeds prior to movement of plant bugs into cotton. Cotton fields in the treated areas and in untreated nine-square-mile areas were sampled for tarnished plant bugs weekly during June and July of all three years. Overall mean numbers of tarnished plant bug adults and nymphs were significantly lower in cotton in the treated areas. The average reduction in overall mean numbers of plant bugs was 45.5 and 47% for adults and nymphs, respectively, for the three-year period. Grower costs for insecticides used to control plant bugs were lower in cotton in the treated test sites in all three years. Elimination of broadleaf weeds was found to be an effective method for reducing numbers of plant bugs in cotton. However, it did not reduce numbers of tarnished plant bugs in any year to a level in cotton where additional control with insecticides was not needed.