Tomatoes are the most popular vegetable grown in home gardens in the U.S. If you've tasted one, you know that the flavor of a fresh-picked, ripe homegrown tomato is orders of magnitude better than anything you can get at the supermarket. Unfortunately, tomatoes are also vulnerable to a number of pests and diseases. Fusarium wilt is one of the most widespread and difficult to control.
Fusarium (Fusarium oxysporum sp. Lycopersici) is a soil-borne disease that clogs the vascular tissue of a tomato's stem, blocking the flow of water up and down the plant. Slice open a tomato stem lengthwise, and there are brown stripes – the fungus – clogging this tissue, while the pith of the stem remains white.
Photograph courtesy of Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org.
The disease appears during warm, wet weather, when temperatures stay in the 80s and 90s F., usually just as the first tomatoes begin to mature on the vine. The wilting starts on one side of the plant or one side of a leaf and works its way from the bottom of the plant up to the top. Leaves will yellow, then brown. Plants are stunted and will not fully mature or provide much fruit.
The plants do not transmit the fungus between them. It enters though root contact with the soil, though it can be spread to uninfected soils via insects or by using stakes, cages, or tools that have infected soil clinging to them. Fusarium is more likely to appear in soils high in nitrogen and low in potassium, and in sandy soils. It can live in the soil for more than 10 years.
There is no cure for fusarium. Affected plants will die. Prevention is the best way to avoid the disease.
Photograph courtesy of Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org.
Strategies for Preventing Fusarium Wilt:
Choose fusarium-resistant tomato varieties. These are marked in seed catalogs as "VF." The plant tags on transplants at the garden center should also indicate if a plant is fusarium resistant. Varieties that are include 'Burpee VF', 'Better Boy', 'Celebrity', 'Small Fry', and 'Supersonic'.
Rotate your crops. Don't plant tomatoes or other Solanaceae family plants such as potatoes, peppers, or eggplant in the same place each year. Allow at least four years before planting members of this plant family in the spot again.
Grow tomatoes in containers and use sterile, soil-free potting mix. Don't reuse the mix again for these kinds of vegetables. Buy new every year.
Test your soil to ensure there's the right balance of nutrients, especially nitrogen to potassium.
Solarizing the soil once fusarium has been identified is an option worth trying, but may not completely kill the fungus.
Once a plant has the disease, there's nothing you can do besides pulling it out. Use a 10% bleach solution to thoroughly clean everything that might have touched the soil around the plant: stakes or cages, trowels, hand forks, pruners, gloves, and the pot if container-grown. Don't put it in the compost; the average home compost pile won't get hot enough long enough to kill the fungus. Put it in the trash instead.
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Justin Hancock, Costa Farms garden guru Photograph: Costa Farms
If looking for a plant that provides more bang for your buck, look no further than Norfolk Island pine. Justin has written a great article on this plant, click here to read it.
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