Tomatoes are one of the most popular vegetables when it comes to urban farming. They taste delicious, produce abundantly, and are versatile in the kitchen (if they don’t get eaten in the garden first). Because of their popularity and need for a sunny growing spot, they often are planted in the same spot from year to year.
Unfortunately, growing tomatoes in the soil spot using the same soil year after year is an invitation for disease – especially fusarium wilt and verticillium wilt. While they are similar in their causes and symptoms, there are some differences we’ll be exploring in this week’s tip.
Fusarium wilt is more common in Southern climates and can affect a variety of plants including cucumbers, legumes, sweet potatoes, and of course tomatoes. It generally occurs with warm air and soil temperatures. Leaves start to yellow at the base (sometimes only on one side of the plant) and spread upwards as the disease progresses.
Verticillium Wilt is more common in Northern climates and is also characterized by yellowing leaves at the bottom of the plant, though the yellowing is more uniform with verticillium wilt. It typically develops during cooler summers.
Because of the similarities in symptoms between these two wilts, sometimes laboratory tests are required to determine the exact wilt fungus disease afflicting the plant. Both types can be spread with contaminated seeds, soil, or transplants.
Treatment of Wilts
The best and most recommended treatment for wilt is to rotate your tomatoes and grow them in a new location. This will give the contaminated soil time to rest and for the pathogens to die off without a suitable host. Do not grow any other plants in the nightshade family in the same spot so avoid planting peppers and eggplant in that area as well. Depending on the prevalence of the fungus, you may need to wait multiple seasons for the pathogen level to decrease to a low enough level to start growing tomatoes again.
If another location is not available, you can also grow your tomatoes in large containers with lots of clean, rich, organic material and good drainage. We recommend using the EarthBox and its accompanying staking system.
Another very good alternative is to choose wilt resistant varieties of tomatoes so that the wilt persists, your plants will be healthier and hang on longer before succumbing to the virus. Often times on seed catalogs, you’ll see the letters “V” or “F” listed beside the variety name indicating Verticillium and Fusarium wilt resistance respectively. If possible, we highly recommend planting in a new spot and/or using large containers.
In more extreme cases, you can sterilize and/or solarize the soil. This involves heating up the soil to at least 180F with most commercial farmers doing this through a specialized steaming process. A similar result can be achieved through solarization in Tip #92, but in our Northern climate, will take a full season and may not the most effective due to the limited time to reach an adequate temperature. We don’t recommend putting any of your soil in your home residential oven. Not only can it stink up your house if you cook it too long, it can be messy, can’t accommodate a large volume, and is often way too impractical for the volume and quality control required.
Cover Image by Glenn, used under its Creative Commons license.