Cause The soft-rot bacterium, Pectobacterium carotovorum subsp. carotovorum (syn. Erwinia carotovora var. carotovora), enters through natural openings or wounds caused by insects and equipment. Pseudomonas spp. have been isolated from diseased roots and are thought to actively infect the host. Prolonged moisture from rain or irrigation and mild temperatures encourage disease development. Insects, tools, rain, clothing, or affected plant tissue can spread the bacteria. These bacteria can survive in soil and plant debris.
Symptoms Any plant part can be affected, but the most serious economic loss is from storage root infections. Plant tissue at first appears water-soaked and rapidly breaks down into a soft, mushy rot. Secondary invaders may also attack. An offensive odor usually is present.
Cultural control
- Practice rotations so that infected crop resides have time to break down.
- Set out plant rows that will allow good air drainage.
- Cultivate carefully to minimize injuring plants.
- Control frequency and source of irrigation water.
- Avoid frequent irrigation during storage root development.
- Time irrigation to allow the plant portions aboveground to dry rapidly.
- Use well water, which generally is free of bacteria.
- Avoid stagnant water sources.
- Keep storage house humidity between 90% and 95% and the temperature between 32°F and 39°F.
Biological control
- Bexfond at 7 to 14 fl oz/A. O