Corn and cotton response to drift rates of non-desired herbicide applications

Journal or Publishing Institution: Proceedings of the Southern Weed Science Society

Study: https://web.archive.org/web/20190606183640/http://www.swss.ws/wp-content/uploads/docs/1999%20Proceedings-SWSS.pdf

Author(s): Rowland Jr., C.D., Reynolds, D.B., and Blackley Jr., R.H.

Article Type: Study

Record ID: 2386

Abstract: Herbicide spray drift is a major concern in the application of agricultural herbicides. In Mississippi, many corn, soybean, and cotton fields are located in close proximity,thus herbicides used in one crop may contact non-target crops by drift. The use of transgenic crops in agriculture has increased dramatically over the past few years. Transgenic crops are
useful tools in weed management; however, problems may occur when transgenic crops are planted in close proximity to susceptible crops. Herbicides that can be applied over the top of resistant varieties may drift into susceptible crops causing damage. These factors may further be complicated by aerial applications. Field studies were conducted in 1998
at the Plant Science Research Center at Mississippi State University and at the Black Belt Experiment Station near Brooksville, MS, to evaluate the effects of sublethal concentrations of various herbicides on cotton (Gossypiumhirsutum L.) and corn (Zea mays L.) growth, development and yield when applied at various growth stages. Treatments were
arranged in a factorial arrangement in a randomized complete block design with four replications. Plots were 12 by 40 feet and all applications were applied at 15 gallons per acre. Factor A consisted of herbicide rates. Rates of Roundup (glyphosate) used in both corn and cotton were 0.375, 0.187, 0.093, 0.046, and 0.023 lb ai/A. Staple (pyrothiobac) rates used in corn were 0.5, 0.25, 0.125, 0.0625, and 0.0313 oz ai/A. Factor B consisted of growth stages at time of application. Application timing in corn included 2-leaf, 6 to 8-leaf, and 12 to 15-leaf growth stages, and in cotton included cotyledon,pinhead square, and early bloom. Plant height and visual injury were determined 7, 14, and 28 days after each application timing,and machine harvested yield was determined to evaluate the effects of the herbicides. Corn visual injury was greater with 0.093 lb ai/A and higher rates of Roundup, and the highest application rate reduced yield 39 to 86%. In general, as the rate of Roundup in corn increased, yield decreased. Corn visual injury was greater at the
2 and 6 to 8-leaf growth stage for all rates of Staple than at the 12 to 15-leaf growth stage. The greatest corn yield reductions for all rates of Staple were observed at the 6-8 leaf growth stage, and was reduced 41 to 89% by the highest rate. No visual injury was observed with Roundup applied in cotton,regardless of rate or application timing. Yield was reduced 20% by the highest application rate of Roundup in cotton.

Keywords: Zea mays L. (corn), Gossypiumhirsutum L. (cotton), drift rate, herbicide, Roundup, yield, transgenic crops

Citation: Rowland Jr., C.D., Reynolds, D.B., and Blackley Jr., R.H., 1999. Corn and cotton response to drift rates of non-desired herbicide applications. Proceedings of the Southern Weed Science Society, 52, p.30.