By Top Crop Manager
Sept. 3, 2013 - Alberta Agriculture and Rural Development has confirmed Goss's wilt has been found in Alberta. Prior to this discovery, Goss's wilt infections have been limited to the Red River Valley in Manitoba.
Depending on weather conditions and hybrid susceptibility, this bacterial wilt of corn leaves may cause only minor problems or it may result in devastating damage, such as yield losses approaching 50 per cent.
Several conditions must be present for Goss's wilt to produce significant damage. If the bacterium is already present in the field and a susceptible hybrid is planted in the field, the next main contributing factor is severe weather. Wind, sandblasting and hail create wounds for the bacteria to enter. Wet weather and high humidity are also needed for escalation of disease development.
Early season infections can result in discoloured vascular tissue within the stalk. Those cases show a buildup of bacteria in the vascular bundles that inhibits the plant's ability to transfer water. Stunted growth and wilting as if drought stressed is another symptom to watch for.
Midseason signs and symptoms include distinct dark green to black "freckles" within or just outside of leaf lesions. Shiny or glistening patches of dried bacterial ooze on the lesions, similar to a thin layer of varnish, can also be observed. Other signs of infection are water-soaked streaks accompanied by tan-to-gray lesions that run lengthwise on the leaves.
In-season management choices for Goss's wilt are very limited, so understanding your options is vital.
"A fungicide application will not work on bacterial diseases such as Goss's wilt," says DuPont Pioneer agronomist Nicole Rasmussen. "The best strategy is selection of a hybrid containing native resistance to the disease and incorporating crop rotation and tillage to minimize survival of the bacteria.
Reducing corn residue through crop rotation or tillage is another management practice that helps combat the disease. One practice that can increase prevalence of Goss's wilt is corn-on-corn acres where the bacteria can overwinter in the remaining residue. Good weed control is very important because weeds such as green foxtail or barnyard grass are hosts for this bacterium. Rasmussen also suggests harvesting and tilling infected fields last and then cleaning your equipment to help avoid spreading the pathogen to uninfected fields.
"This disease can overwinter in the soil and crop residue, so if growers have a problem, they should look at disease ratings prior to purchasing corn for 2014 as it could be an issue again next year," says Rasmussen.