|Raid, R -|
Submitted to: International Society of Sugar Cane Technologists Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2013
Publication Date: June 25, 2013
Citation: Raid, R.N., Comstock, J.C. 2013. Evaluation of fungicides for control of orange rust on sugarcane. International Society of Sugar Cane Technologists Proceedings. 28:1-9. Interpretive Summary: Sugarcane orange rust is a serious economic disease in South Florida that was introduced in 2007. Fungicides treatments were evaluated as a means of controlling orange rust until resistant cultivars can be developed. Data indicate that the strobilurin fungicides provided the highest level of control, followed by strobilurin/triazole and strobilurin/carboxamide combinations, and finally, the triazole fungicides alone. For multiple fungicide treatments, spray intervals from 14 to 21, or even 28 days, were effective in reducing losses. Thus, fungicides offer a mechanism of control.
Technical Abstract: Sugarcane orange rust, caused by Puccinia kuehnii, was initially reported in the Western Hemisphere in 2007, when it was first observed in Florida. Since that time, it has affected several commercially important cultivars, notably CP 80-1743, CP 72-2086, CP 89-2143, CP 88-1762, and CP 78-1628. During 2010, these cultivars accounted for nearly 71% of Florida’s sugarcane holdings. With host-plant resistance a long term goal, the sugarcane industry is in desperate need of additional rust management tools. A series of fungicide trials were conducted over a period of four years to investigate the feasibility of fungicides serving as a viable, economic means of control. All experimental units consisted of two rows of cane 15 m in length and were replicated four times in a randomized complete block design. Fungicide treatments consisted of select candidates from three major classes of fungicides, the strobilurins (FRAC group 11), the triazoles (FRAC group 3), and the carboxamides (FRAC group 7), alone and in combination and/or alternation. Fungicide applications were performed using a CO2 backpack sprayer and were initiated following canopy closure and the initiation of the orange rust epidemic. Rust severities in the trials ranged from moderate to very severe on the susceptible cultivars selected for testing, CP 80-1743 and CL 85-1040. Results indicate that the strobilurin fungicides provided the highest level of control, followed by strobilurin/triazole and strobilurin/carboxamide combinations, and finally, the triazole fungicides alone. For numerous fungicide treatments, spray intervals were expanded from 14 to 21, or even 28 days, with minimal loss in efficacy. In separate trials using the strobilurin fungicide pyraclostrobin, fungicides were demonstrated capable of reducing orange rust losses by as much as 40%. While economic factors will ultimately be an important consideration, levels of orange rust control obtained in these studies show promise regarding prospects for fungicides as a potential management tool.