2011 Field Crops Rust Symposium:
Determining Yield Loss Caused by Brown Rust in Production Fields of Sugarcane
Presenting Author: M. P. GRISHAM
Coauthor: R. M. Johnson
Affiliation: USDA-ARS, Sugarcane Research Unit, Houma, LA, USA
Infections of Puccinia melanocephala, the causal agent of brown rust, appear on Louisiana sugarcane in the spring. Disease expression is usually limited to 2–3 months until temperatures exceed those favorable for spore production. The affected sugarcane is harvested 4–6 months after rust symptoms disappear. Precision agriculture techniques were used to determine the effect of brown rust on yield in four production sugarcane fields. A handheld computer equipped with a GPS (global positioning system) receiver and mapping software was used to determine experimental field boundaries and establish grid-sampling points. Field size varied from 0.7 to 8.9 hectares, and grid size varied from 0.02 to 0.4 hectares. At each grid-sampling point, a soil sample was taken and rust ratings were made weekly for 6 or 7 weeks. Experimental plots were harvested utilizing a single-row, chopper harvester. The total weight of harvested cane in each plot was determined using a single-axle, high-dump billet wagon containing three electronic load sensors and equipped with a device to collect a billet subsample for sucrose quality analysis. Rust ratings and cane yield varied significantly among sampling points within and between fields. Sucrose and cane yields were negatively correlated to the rust ratings. In addition, overall fertility levels of each location were variable and positively correlated to rust severity. The combined data show the adverse effects of rust on cane and sucrose yields and that sugarcane growers who apply fertilizer at rates exceeding plant requirements will increase the severity of rust in their fields.