Disease Management

Corn Stewart's Wilt

Stewart’s Bacterial Wilt of Sweet Corn

Stewart’s Wilt of sweet corn, caused by Pantoea (Erwinia) stewartii, continues to be a problem in most sweet corn producing areas of the Northeast. The disease is caused by a bacterium that can spread systemically throughout the plant. Symptoms appear at any stage of plant growth. Seedling wilt occurs at or before the 5-leaf stage as the bacterium enters the plant through wounds created by the corn flea beetle (Chaetocnema pulicaria), spreads to the developing stalk, and kills the growing point. The seedling may develop linear pale green to yellow streaks, wilts, and dies. The leaf blight phase of Stewart’s Wilt occurs when older plants are infected. Long, white to yellow streaks develop along leaves and entire leaves may dry up and die, suggesting drought or nutritional stress. Highly susceptible varieties may exhibit vascular discoloration in stems and at leaf nodes. Loss of leaf tissue results in small, poorly filled, and unmarketable ears. Greatest loss occurs when the plants are infected as seedlings; damage is reduced as plants mature. 

P. stewartii overwinters in the alimentary tract of adult corn fleas beetles, not in the soil or in plant debris. Severity of Stewart’s Wilt depends on three factors: 1) the winter temperatures prior to planting 2) the amount of disease the previous season and 3) cultivar susceptibility. If cold winter temperatures occur, fewer flea beetles survive to transmit the disease. The amount of disease in the previous season determines the percentage of emerging beetles carrying the bacterium. Hybrids with greater levels of resistance can tolerate more infection with less yield loss. Resistance restricts the movement of the bacteria in the plant.

Management

• Grow varieties that are resistant to the disease. Information on cultivar susceptibility is available online at http://www.sweetcorn.uiuc.edu/stewarts .
• Use insecticides to control flea beetles, particularly on susceptible varieties in the seedling stage. This is not as effective as resistant varieties, but reduces losses where susceptible hybrids must be planted.
• Scout frequently for flea beetles as rapid growth of leaf tissue makes untreated surfaces available.
• Imidacloripid (Gaucho) seed treatments provide systemic control of corn flea beetles and reduce the severity of Stewart’s Wilt.

References:

Zitter, T.A. 2002. Stewart’s Bacterial Wilt-Still a Problem after 107 Years. http://www.vegetablemdonline.ppth.cornell.edu .