Stewart's Wilt - Management & Control

Management & Control

Forecasting should be done to determine the severity of Stewart's bacterial leaf blight. Prediction relies on temperatures from previous winters. A way to determine if an outbreak of Stewart's wilt will occur is to add the average temperatures in December, January, and February. If you find them to be greater than 95 degrees Fahrenheit, expect an outbreak. If you get a sum of the average temperatures to be less than 90 degrees Fahrenheit, there's usually no need for control. This forecasting method solely relies on the corn flea beetle's ability to overwinter. As you'd imagine, a winter with numerous days below 0 degrees Fahrenheit will reduce beetle populations and lessen the risk for disease. On the other hand, high amounts of snow cover and heavy crop residues are thought to favor beetle survival; even when temperatures are lower than 0 degrees Fahrenheit. When forecasting for this disease, snow cover and temperatures must be analyzed before assessing control of the disease.

All sweet corn varieties are susceptible to wilt in the first leaf stage. Susceptibility decreases and natural control is obtained as plants grows older. External disease control is conducted by insecticide spraying to stop early feeding of overwintering flea beetles. Insecticides should be sprayed as soon as corn first breaks the soil surface. When establishing control measures, spraying should be repeated several times to regulate the presence of the insecticide products in the field. Common insecticides used for control of Stewart's wilt are clothianidin, imidacloprid and thiamethoxam. These insecticides are most effectively used at rates of 1.25 (mg ai/kernel), with clothianidin being the most effective at that rate. Application rates on the labels may vary a little, so follow the label rates for each insecticide. Better results are obtained when seeds are sprayed prior to germination. In furrow spraying and post-germination foliar spraying may not be effective.

Although insecticides are effective, resistant hybrids are the best means of disease control. There's less chance of resistance and they've all together showed better results for protection against Stewart's disease. Hybrid varieties of sweet corn are also available for control. Dent corn hybrids are more resistant to the disease than sweet corn and hence, do not require insecticides.