Location: Sugarcane Research Unit
Title: Herbicide options for suppressing bermudagrass in sugarcane Author
Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: January 25, 2013
Publication Date: January 28, 2013
Citation: Dalley, C.D. 2013. Herbicide options for suppressing bermudagrass in sugarcane. Proceedings of the Southern Weed Science Society 66th Annual Meeting. Available online: http://www.swss.ws/wp-content/uploads/docs/2013%20Proceedings-SWSS.pdf Technical Abstract: Bermudagrass is a problematic weed in Louisiana sugarcane. The most effective herbicide options are limited to the fallow period prior to planting. Frequently, efforts to eliminate bermudagrass from fields during the fallow season are unsuccessful. This subjects newly planted sugarcane to competition at a time when it is becoming established and is most vulnerable. Trials were conducted to evaluate herbicide options and application timing for bermudagrass control to determine their impact on sugarcane yields. In 2008, three trials were conducted comparing metribuzin (1.5, 2.25, and 3 lb ai/ac), clomazone plus diuron (1.25 plus 2 lb ai/ac), terbacil (1.8 lb ai/ac), and diuron plus hexazinone (1.4 plus 0.4 and 1.87 plus 0.53 lb ai/ac). Treatments were applied on February 11 and 12, 2012 to sugarcane planted in the fall of 2011. Treatments were broadcast applied either to undisturbed soil, or after row sides had been cultivated twice to break up stolons, with and without a broadcast application of pendimethalin (2 lb ai/ac). Experiments that were cultivated prior to application were lightly cultivated a third time to incorporate herbicides. At the time of application, bermudagrass had just begun to green up and sugarcane was 3 inches in height to the uppermost leaf collar. In 2009 and 2011, similar trials were conducted comparing the same herbicide treatments, except that no cultivation or pendimethalin were included. In 2009, treatments were applied on three dates four weeks apart (February 9, March 9, and April 8) to determine if application timing affected bermudagrass control, sugarcane injury, or yield. On the February application date, both bermudagrass and sugarcane were dormant. On the March application date, bermudagrass had greened up and stolons averaged 5 inches in length and sugarcane averaged 1 inch to the uppermost leaf collar. On the April application date, bermudagrass stolons averaged 10 inches in length and sugarcane measured 4 inches. In 2011, the same herbicide treatments were applied on February 15 to dormant bermudagrass and sugarcane. At 4 WAT, clomazone plus diuron provided the best bermudagrass control (85%) followed by 3 lb/ac of metribuzin (72%) and diuron plus hexazinone at 1.87 plus 0.53 lb/ac (69%). Bermudagrass control was least with metribuzin at 1.25 lb/ac (44%). In the 2008 trial, cultivation only slightly improved control compared to no cultivation, and the application of pendimethalin did not improve control. All treatments increased yield compared to the non-treated control. No differences in yield occurred due to cultivation or pendimethalin treatments. Application of clomazone plus diuron increased sugar yield (11,150 lb/ac) by 41% compared to the non-treated control (7,910 lbs/ac). Increasing metribuzin from 1.5 to 2.25 lb/ac increased sugar yield (10,060 to 10,780 lb/ac), but no further improvement occurred when 3 lb/ac were applied (10,520 lb/ac). When application timing was evaluated in 2009, average control ratings decreased from 67 to 54 to 41%, respectively, for February, March, and April application dates. In this study, sugar yield was greatest following February or March herbicide applications compared to the April application date. This was especially true for the clomazone plus diuron treatments where sugar yield decreased from 11,600 to 10,100 to 9,200 lb/ac, respectively, for February, March, and April application dates. This loss in yield was due to a combination of increased sugarcane injury and reduced bermudagrass control. In all studies it was apparent that even while excellent control of bermudagrass was not achieved, tremendous gains in sugar yield could be attained through suppression of bermudagrass in sugarcane.