Bottom Rot

With a name like bottom rot, you just know it isn’t going to end well.


Bottom rot is a fungal disease of lettuce and other leaf vegetables, caused by the Rhizoctonia solani fungi. This is the same fungi that causes damping off disease. These fungi live in the soil and are 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 that are 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 and in nearby soil. 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 total collapse of the plant.


Controlling bottom rot

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

• space plants to provide good air flow
• clear out decomposing plant material before planting
• avoid overwatering
• avoid overhead watering
• do not use more nitrogen than is needed
• control nearby weeds, which may host the pathogen
• improve drainage and soil structure with plenty of organic material
• use a 3-year crop rotation to break the disease triangle

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