|Richard Jr, Edward|
Submitted to: Weed Technology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 1997
Publication Date: N/A
Interpretive Summary: Bermudagrass and johnsongrass are two of the most troublesome weeds of sugarcane in Louisiana because conventional herbicide treatments are ineffective in eliminating these weeds from within the crop. In two studies replicated over time, at-planting, fall applications of sulfometuron at 150 g ai/ha and at-planting followed by spring applications sof thiazopyr at 560 g ai/ha controlled johnsongrass emerging from rhizomes better than imazapyr at 280 g ai/ha and standard treatments of atrazine, metribuzin, and a mixture of pendimethalin and atrazine. An at-planting application of sulfometuron was also effective in controlling bermudagrass emerging from rhizomes and stolons. Where johnsongrass is not controlled, sugar yields by the second-ratoon crop may be reduced by as much as 50%; bermudagrass can reduce yields by 15%. If labelled for use in sugarcane, at-planting applications of sulfometuron and thiazopyr would allow growers to minimize the economic impact of bermudagrass and johnsongrass on sugarcane production in Louisiana at herbicide rates that are significantly lower than currently used standards.
Technical Abstract: At-planting applications of sulfometuron at 110 to 150 g ai/ha controlled more bermudagrass and johnsongrass emerging in sugarcane from vegetative propagules in the fall than standard applications of atrazine at 2240 g ai/ha (no control), metribuzin at 2580 g ai/ha, and pendimethalin at 2240 g ai/ha. Similar responses were not obtained with fall applications of imazapyr at 280 g ai/ha and thiazopyr at 560 g ai/ha. Bermudagrass contro in the spring was higher than the standard treatments only when an at- planting application of sulfometuron at 150 g/ha was followed by a March application at 30 g/ha. Rhizome johnsongrass in the spring was controlled 44% following standard applications of metribuzin and pendimethalin, 73 to 94% with sulfometuron in the fall and metribuzin in the spring, and 82 to 92% when the spring application of metribuzin was replaced with sulfometuron at 30 g/ha. At-planting followed by spring applications of imazapyr controlled johnsongrass 81% in the spring. Significant (>10%) crop injury was observed only when imazapyr (42%) and sulfometuron (16 to 32%) were applied to emerging sugarcane in the spring. Sugarcane stalk numbers, stalk heights, and ultimately cane and sugar yields were increased when compared to the standards following all sulfometuron treatments and when thiazopyr was applied as a sequential treatment.