How to Control Fusarium Wilt in the Garden

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Learn how to Identify and Treat Fusarium Wilt

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Out for a garden walk, you look at your yellowing tomato plant and think, “It’s just an old leaf; it’s supposed to do that.” But then you see it on another plant and on new leaves, too. Wilting plants and yellowing leaves are hallmarks of fungal diseases like Fusarium wilt. It happens in summer as the temperatures rise. Healthy tomatoes, peppers, eggplants, cucurbits, beans, and even cabbages can be affected. If you notice something amiss and suspect wilt, read on!

What Is Fusarium Wilt?

Fusarium wilt is a fungal pathogen. Most Fusarium wilts home gardeners experience are caused by the species Fusarium oxysporum. They are further categorized by their preferred host. They are called host-specific forms, for which the scientific abbreviation is ‘f. sp’.  

You may see F. oxysporum f. sp. melonis for the variety that attacks melons, or f.sp. Lycopersici for the variety that attacks tomatoes (the botanical name for tomatoes is Solanum lycopersicum

To further complicate things, Fusarium wilt of tomatoes has three “races.” Plants may be susceptible to or resistant to one race of F. oxysporum but not another. 

Fusarium fungi thrive when the soil temperatures warm in summer. About 75-85 degrees is their sweet spot. Soil temperatures below 70 will slow their growth. 

How Does Fusarium Wilt Infect and Harm Plants?

Fusarium hyphae attack a plant by entering the water-conducting tissue in the roots called the xylem. Hyphae gain entry at wounds in the roots caused by harmful nematodes or other mechanisms like cultivation. Shallow roots are particularly susceptible. I like to blame the moles. 

The fungus then clogs up the xylem, basically reducing the movement of water through the plant. Leaf yellowing is caused by toxins the fungus gives off. 

Fusarium vs. Verticillium Wilt

If you have been a gardener for a while, you have probably heard of and maybe had problems with Verticillium wilt. This similar disease can infect many of the same plants, trees, and shrubs and is caused by fungus in the genus Verticillium

Unfortunately, Fusarium wilt and Verticillium wilt present identical symptoms. The only way to positively identify the culprit is to send a sample to your state’s university plant laboratory for culturing. However, both affect plants in a similar fashion. The prevention and treatment options are also the same. 

How Does Fusarium Wilt Spread?

Like any fungus, Fusarium reproduces by making spores. Some of these spores have rigid, thick walls and can live for years in the soil, persisting even in dry soil conditions. 

Other spores are thin-walled and are spread in contaminated soil, splashed by water, or hitch a ride via infected soil that is not cleaned from garden tools. Check out this factsheet from the University of California for a more detailed look at how the fungus spreads.


Fusarium wilt can initially look like older, lower leaves naturally aging and yellowing. As summer progresses, keep an eye out for these telltale signs.

Look for These Signs of Fusarium Wilt:

  • Initially, plants may wilt during the hottest part of the day but appear to recover overnight. This symptom may be present on only one side of the plant and can look like simple underwatering at this stage.
  • Yellowing leaves appear, often from the outer areas of the plant first. Again, this may be on only one side of the plant or on one portion of a compound leaf.
  • Some leaves may brown after yellowing, although this does not always happen. 
  • Inspecting the vascular tissue in the base of the stem reveals brown or red splotching. 
Fusarium wilt of tomatoes. Tomato plants with yellowing leaves.
Photo by AmBNPHOTO/Shutterstock
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Control and Prevention

Fusarium wilt cannot be cured, but its effect can be mitigated. Follow these integrated pest management ideas. Your local extension agent or program can provide more information tailored to your area. 

Prevention and Monitoring

Of course, we would rather not have any Fusarium spores or hyphae at all. Monitoring will alert you to a developing problem. Prevention ideas include: 

  • Purchase transplants and seeds from a reliable supplier. Seeds can be heat-treated or fumigated by the vendor to ensure no spores are hiding in your seed packets. A professional nursery or grower will monitor and take steps to keep their stock Fusarium wilt-free. 
  • Clean your tools. Do this for tools used in potentially contaminated areas before moving to a new spot and before storing them for the winter. After scrubbing them, dip your tools in a mild bleach solution.
  • Fusarium fungi prefer acidic soils, so liming to raise your pH to be neutral or slightly alkaline  (soil pH of 7 or a touch higher) can limit their activity. Don’t overdo it. Highly alkaline pH can limit plant nutrient availability.

Choose Resistant Plants

Gardeners have many options when choosing which varieties to plant; some have been bred to resist Fusarium. The seed catalog or website listing will often state a particular cultivar’s resistance to Fusarium, Verticillium, harmful nematodes, and many other pests and diseases

If you have previously experienced a problem with a particular pest, choosing a resistant variety is perhaps one of the most important and easiest ways to minimize the impact. 

You may see the resistance abbreviated as ‘F’ or ‘FNV.’ The latter would indicate resistance to Fusarium, nematodes (the bad ones), and Verticillium. Seeds labeled ‘TMV’ would show resistance to the tomato mosaic virus

Tomato seed may be labeled ‘F’, ‘FF’ or ‘FFF’ to indicate resistance to one or more races of F. oxysporum f.sp. Lycopersici. Check the key or legend of your seed catalog to confirm. 

Treatments for Fusarium Wilt

There is no “cure” for Fusarium wilt. Fungicides are not effective. Your best bet is to limit the spread and food source, and choose resistant plants, as discussed above. 

Get rid of infested plants

  • Remove infected plants. Don’t compost them. Bury them (somewhere else) or burn them. Getting rid of these infected plants can reduce the amount of spore present next year and slow the spread.

Move plants around

  • Rotate your plants. For example, if you experienced Fusarium wilt in your tomatoes, move next year’s tomato planting to a new area and grow a non-susceptible plant in the old spot. (This is known as “crop rotation.”)
  • Fusarium is host-specific, so the fungus that attacked your tomatoes likely won’t bother your melons, beans, etc. Don’t replant a susceptible species for several years. Avoid planting a related species in that location, like following tomatoes with peppers (they are both members of the Nightshade family, Solanaceae).

Use soil solarization

Fusarium spores in the soil may be killed by a technique called soil solarization. Basically, bare ground is covered in clear plastic to harness the sun’s rays and heat the earth, killing the pathogen. 

The process can take several weeks during the summer, so you may have to forfeit the peak of the growing season. However, you can still plant a late crop of delicious lettuces, kale, and peas, right? 

More information on this method and how to perform it can be found in this document from the University of California’s IPM program

Fusarium wilt can be challenging if allowed to spread in your garden. Take the actions given above early. Choosing resistant varieties, rotating crops, and cleaning your tools will go a long way toward keep Fusarium risk low.

About The Author

Andy Wilcox

Andy Wilcox is a flower farmer and master gardener with a passion for soil health, small producers, forestry, and horticulture. Read More from Andy Wilcox

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