Bottom Rot

With a name like bottom rot, you know it won't end well.

Bottom rot is a fungal disease of lettuce and other leaf vegetables caused by the Rhizoctonia solani fungi. This is the same fungus that causes damping off. It lives in the soil and can be a big problem in warm, moist conditions.

Plants affected by bottom rot

In addition to lettuce, bottom rot can wipe out your Chinese cabbage, escarole, broccoli, radish, collards, Brussels sprouts, cauliflower, and turnip crops. The Rhizoctonia solani fungus also attacks potatoes, onions, beans, and corn.

Early signs of bottom rot on iceberg lettuce (Rasbak) CC BY-SA 3.0 CC BY-SA 3.0

Symptoms of bottom rot

At first, all you may see is some wilting of outer leaves. Closer inspection will show reddish-brown, sunken lesions on the midribs of leaves touching the soil. Brown or white fungal tissue may be visible, and lesions may discharge a light brown ooze. Leaf spots and brown lumpy bits may also be present on the plant. The fungus grows inward, toward the center of the head or body of the plant. The damaged plant tissue then becomes susceptible to other soft rots, causing a total collapse of the plant.

Controlling bottom rot

Fungicides are ineffective against bottom rot, so prevention is your only option. These tips will help protect your leafy bottoms:

• Clear out decomposing plant material before planting.
• Improve drainage and soil structure by adding organic material.
• Space plants for good airflow.
• Control nearby weeds which may host the pathogen.
• Irrigate at ground level and avoid overhead watering.
• Do not use more nitrogen than is needed.
• Use a 3-year crop rotation to break the disease triangle.

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As with all bottoms, keep them dry, and they will be happy.