Edward P. Richard

Herbicides as Ripeners for Sugarcane

Abstract Chemical ripening of sugarcane is an important component to profitable sugar production in the United States as well as other sugarcane industries throughout the world. Harvesting of sugarcane often begins before the sugarcane reaches the desirable maturity level. This is especially true in the Louisiana sugarcane industry where the window for harvesting is limited because of the risk of freezing temperatures encountered in a temperate climate. Research on the application of chemicals, mostly of herbicide origin, to enhance sucrose accumulation (ripening) or limit flowering to conserve stored sucrose has been conducted for more than 60 yr. The only sugarcane ripener currently registered for use in the United States is glyphosate applied before harvest. The herbicide fluazifop is used as the primary ripener of sugarcane in South Africa. The herbicides glyphosate, fluazifop, and sulfometuron-methyl and the growth regulators ethephon and trinexapac-ethyl are registered for use in Brazil. There is a continuing need to evaluate sugarcane ripeners to increase the utility of currently registered ripeners and to find additional ripeners for use by sugarcane industries. The need for alternatives to glyphosate is especially critical before a glyphosate-tolerant sugarcane can be utilized to improve control of problematic weeds. Nomenclature: Ethephon; fluazifop; glyphosate; sulfometuron-methyl; trinexapac-ethyl; sugarcane, Saccharum interspecific hybrid.

Control of Rhizome Johnsongrass (Sorghum Halepense) in Sugarcane with Trifloxysulfuron and Asulam

It has been suggested that trifloxysulfuron might increase the efficacy of asulam for control of johnsongrass. Container and field studies were conducted to determine the efficacy of POST applications of trifloxysulfuron and asulam for johnsongrass control in sugarcane. Asulam was applied at 460 and 920 g ai/ha to container-grown johnsongrass plants, with and without 8 g ai/ha of trifloxysulfuron. Combinations of asulam and trifloxysulfuron generally reduced johnsongrass height, rhizome length, and biomass more than when either was applied alone. Results suggested that combinations of asulam and trifloxysulfuron were synergistic in their control of johnsongrass biomass 8 wk after treatment. In a sugarcane field heavily infested with rhizome johnsongrass, asulam was applied at 1,800, 2,800, and 3,700 g/ha with and without trifloxysulfuron at 16 g/ha. Asulam plus trifloxysulfuron generally controlled johnsongrass more effectively than either herbicide alone. The control of johnsongrass with asulam at 1,800 g/ha resulted in an increase in sugar yield of more than twice that in the nontreated control. Sugar yield increased further when asulam was applied at 2,800 g/ha or combined with trifloxysulfuron, but application of trifloxysulfuron alone did not increase yield. Combinations of asulam and trifloxysulfuron might slow the spread of rhizome johnsongrass enough to allow an increased number of ratoon crops before sugarcane fields need to be replanted. Nomenclature: Asulam; trifloxysulfuron; johnsongrass, Sorghum halepense L. Pers. SORHA; sugarcane, Saccharum interspecific hybrid ‘LCP 85-384’

Sugarcane Response to Bermudagrass Interference

The competitiveness of three phenotypically different sugarcane cultivars with bermudagrass was determined in field trials. In trial one, bermudagrass biomass was 22% less in CP 70-321 than in HoCP 85-845 in the plant-cane crop, but biomass was 130 to 170% greater in CP 70-321 than in the other two cultivars during the second-ratoon crop. CP 70-321 emerges quickly following planting, which might have reduced bermudagrass growth in the plant-cane crop, but the lower stalk population of CP 70-321 might have promoted bermudagrass survival and growth during the second-ratoon crop. In trial two, there were no differences in bermudagrass biomass when comparing its establishment in the different cultivars. Sugarcane, averaged across cultivar, produced fewer stalks and was shorter when competing with bermudagrass. In the plant-cane crop, stalk populations were reduced 13 to 23%. In the first-ratoon crop, stalk population was reduced 8 to 15%. In the second-ratoon crop, stalk population was reduced 8 to 10%. Bermudagrass interference reduced sugar yields by 8 to 32% in the plant-cane crop, with reductions of no more than 9% in the first- and second-ratoon crops. The greater yield loss in the plant-cane crop in the first production year shows the importance of controlling bermudagrass in the summer fallow period prior to planting and during establishment of the plant-cane crop. Nomenclature: Bermudagrass, Cynodon dactylon L. Pers. CYNDA; sugarcane, Saccharum interspecific hybrids ‘CP 70-321’, ‘LCP 85-384’, ‘HoCP 85-845’.