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Bacterial Wilt (Stewart's Wilt): Kentucky Corn IPM

Bacterial Wilt (Stewart's Wilt)


Symptoms

Sweet corn is much more susceptible to Stewart's Wilt than field corn.

The disease is characterized by leaves showing pale green to yellow streaks with irregular or wavy margins that parallel the leaf veins. The streaks may extend the length of the leaf. These symptoms may resemble drought stress, nutrient deficiency or insect injury. Later, the streaked areas may die and become straw colored; sometimes entire leaves die and dry up.

Bacterial Wilt/ Stewart's Wilt

Infections are most common early in the pre-tassel (whorl) stage, or after tasseling. Early season symptoms include plant death: seedlings infected with Stewart's Wilt wilt rapidly and die. Look for dark brown cavities in the lower stalk pith with no evidence of insect injury on the lower stalk. Infections after tasseling are generally more severe on upper leaves.

Lesions of Stewart's Wilt may be confused with unrelated lesions on hybrids carrying an Ht2 resistance gene to Northern Corn Leaf Blight . To aid in diagnosing Stewart's Wilt, hold leaves to the light and look in the lesions for scratch-like feeding marks of flea beetles (the transmission agents for the disease).

Cause

Bacterial Wilt in Field

The causal agent of bacterial wilt is Erwinia stewartii which is transmitted by the corn flea beetle. The bacterium overwinters in the body of corn flea beetles and is spread by their feeding. The streak symptoms originate from feeding marks of the corn flea beetle. The disease is more prevalent following mild winters. In Kentucky, disease pressure is usually high, but if the winter is very cold so the flea beetles are killed, disease pressure will be significantly lower in the following growing season.

IPM Techniques

References and Additional Information


This site was created and is maintained by Pat Dillon, Department of Entomology, University of Kentucky, S-225 Agricultural Science Ctr North, Lexington, KY USA  40546-0091 (phone: 859/257-3571). Please send questions or suggestions to: pdillon@uky.edu