Cause Erwinia chrysanthemi pv. zeae (syn. = Dickeya zeae = E. carotovora f. sp. zeae), a bacterium that persists on crop residues in soil. Stalk rot is observed sporadically in the Pacific Northwest; a top rot is observed in fields with overhead irrigation using contaminated river, lake, or ditch water. Warm (86ºF to 95ºF) temperatures and high relative humidity promote the development of bacterial stalk rot. Moisture collected in the whorl of overhead irrigation equipment, especially if nitrogen is applied by overhead irrigation, or from heavy dew formation is believed to be the contributing factor for top rot. Top rot has been severe in some fields in Oregon and Washington. Observations in Washington and Oregon indicate the disease frequently is severe in plants when growing on sulfur-deficient soils. The variety 'Jubilee' is very susceptible.
Symptoms Stalk rot symptoms usually appear in midseason. The first and/or second internode above the soil line appears water soaked, turns tan to brown, and becomes soft and mushy. Affected plants suddenly collapse and fall over with their vascular strands still intact. Infected tissue has a foul odor. In the top rot phase, tips of uppermost leaves wilt, followed by a slimy soft rot at the base of the whorl that spreads down into the stalk. Affected plants collapse.
Cultural control
- Avoid overhead irrigation.
- Use well water, if possible, for irrigation.
Chemical control
- Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. O
- Kocide 2000 at 1.5 to 3 lb/A on 7- to 10-day intervals. 48-hr reentry. O