Fusarium wilt

About

Fusarium wilt is a soilborne disease that clogs a plant's water-conducting tissue so it yellows, wilts and dies. Once it is in your soil it stays for many years, so resistant varieties are the main defense.

Also called Fusarium wilt, Fusarium yellows

How to recognize it

Symptoms

Lower leaves turn yellow, often on just one side of the plant or one branch, and plants wilt in the afternoon heat and recover at night at first. The yellowing climbs until the whole plant wilts and dies. Cutting the lower stem lengthwise shows dark brown streaks in the water-conducting tissue.

Often confused with

Verticillium wilt looks almost the same; Fusarium browning tends to be darker and it prefers warmer soil. A lab test is the only sure way to tell them apart.

Worse when

Warm soil (the tomato strain does best around 82°F), and acidic soil makes it worse.

How it spreads

Tough resting spores survive many years in soil and plant debris and move with soil, water, tools and infected transplants; the fungus enters through the roots.

When

Midsummer onward, when soils are warm.

What to do, gentlest first

Prevention works best; most sprays only protect healthy leaves and can't cure infected ones. Always read and follow the product label.

1. Resistant varieties Prevent

   For tomatoes, look for F (race 1), FF (races 1 and 2) or FFF (races 1, 2 and 3) on the label; Clemson recommends FF or FFF. Resistant cabbage varieties exist for Fusarium yellows, and Rutgers says its 'Obsession DMR' basil is highly resistant to Fusarium wilt.

   UC IPM notes cabbage resistance weakens in hot soil.

2. Clean soil and transplants Prevent

   Start with pathogen-free transplants and potting mix. Clemson suggests raising tomato soil pH to 6.5 to 7.0 and feeding with nitrate nitrogen (calcium nitrate) instead of ammonium forms.

3. Long rotation and weed control Prevent

   Keep susceptible crops out of infested soil for three to five years or more, and control weeds like pigweed and crabgrass that can carry the fungus.

4. Soil solarization Prevent

   In sunny, hot areas, UC IPM suggests solarizing the soil under clear plastic before planting susceptible crops.

5. Remove whole plants By hand

   Pull infected plants, roots and all, and destroy them rather than composting. Clean soil off tools.

6. No spray cures it Conventional spray

   UMN and Clemson say there is no chemical control for Fusarium wilt. Skip fungicides and rely on resistance and rotation.

Plants it affects

Basil, Cabbage, Cantaloupe (muskmelon), Chayote, Chickpea, Dewberry, Eggplant, Ginger, Okra, Passion fruit, Peas, Pepper (sweet and chili), Southern peas, Sweet potato, Tomato, Watermelon