By C.M. Ocamb
Cause Pectobacterium carotovorum subsp. carotivorum (syn. Erwinia carotovora subsp. carotovora), a bacterium that enters through growth cracks or wounds caused by cold temperatures, insects, other disease organisms, or by mechanical means. Under warm, humid conditions, uninjured tissue may become infected through natural openings. Prolonged moisture from rain or irrigation and mild temperatures encourage disease development. Insects, tools, rain, clothing, or affected plant tissue can spread the bacteria. The bacteria survive in soil and plant debris.
Symptoms Small, water-soaked areas appear and rapidly enlarge. Tissue becomes soft and mushy, and within a few days the affected plant part may collapse. An offensive odor usually is present.
Cultural control
- Practice rotations so that infected crop resides have time to break down.
- Set out plants in rows to allow good air drainage.
- Cultivate carefully to minimize injuring plants.
- Control frequency and source of irrigation water.
- Avoid frequent irrigations.
- Use well water, which generally is free of bacteria.
- Avoid stagnant water sources.
Chemical control
- Copper formulations (Group M1) are registered for use. Care should be taken with copper products to avoid build-up of copper in soils.
- Champ WG at 1.0 to 1.58 lb/A on 7- to 10-day intervals. 48-hr reentry. O
- 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
- Liqui-Cop at 3 teaspoons/gal water. H
Biological control Efficacy unknown in Oregon.
- Cease at 3 to 6 quarts in 100 gal water. For greenhouse plants only. Preharvest interval is 0 days. 4-hr reentry. O