Bacterial Soft Rot

Bacterial soft rot destroys more crops than any other bacterial disease. 

Commonly occurring in cruciferous, cucurbit, nightshade, and onion families, bacterial soft rot also causes severe pitting in carrots.

Potato with bacterial soft rot (Scot Nelson) Public Domain

Rather than a single disease with a simple cause, bacterial soft rot refers to a collective of bacterial rots caused by Dickeya dadantii (previously known as Erwinia chrysanthemi), Pectobacterium carotovorum, and various Bacillus, Clostridium, and Pseudomonas bacteria. Whichever critter starts this problem, the soft tissues of buds, bulbs, corms, and the rest become liquified, turning your crop into a mushy mess.

Onion infected with bacterial soft rot (Scot Nelson) Public Domain

Symptoms of bacterial soft rot

Like other bacterial diseases, bacterial soft rot is easy to miss in its early stages. As the disease progresses, water spots start to form. Unlike the whitish splash marks left on old wooden furniture, these spots expand, become soft, and sink. These damaged areas may ooze and change color. Discolorations can range from cream to black. And they smell bad.

Bacterial soft rot management

Poor drainage, waterlogged soil, and insufficient airflow can all set the stage for bacterial soft rot. Infected plants must be destroyed and removed. Prevention is worth the effort. The following good cultural practices can significantly reduce the likelihood of bacterial soft rot affecting your plants:

• Use certified clean seeds and seedlings.
• Quarantine and harden off new plants.
• Install resistant varieties.
• Plant at the appropriate times and correct depths. 
• Use recommended plant density.
• Monitor plants regularly for signs of infection.
• Provide adequate airflow through proper pruning.
• Irrigate properly, allowing the soil to dry out between waterings.
• Employ crop rotation to reduce overwintering bacteria.
• Remove weeds.
• Avoid working crops when they are wet.
• Remove infected plants and dispose of them in the trash.
• Clean and disinfect tools regularly.

If bacterial soft rot continues to be a problem in specific areas of your garden, use that space for plants that are generally not susceptible. That list includes beets, corn, and snap beans.