August 10, 2022

Down the Garden Path: Guest columnist series –Keeping tomato plants healthy

It will be some time before we have fresh tomatoes on the vine in the northern Illinois area, so the focus now is keeping plants healthy as they grow. Given enough sun and the right amount of water, tomato plants are easy to grow.

However, the plant is susceptible to several preventable diseases. Two of these are early blight and Septoria leaf spot. Both are fungal diseases that result in leaf spots with eventual loss of leaves and decreased fruit production.

The good news is these diseases can usually be prevented with proper plant care. Fungal diseases develop in wet conditions. Spacing tomato plants so that air can circulate between them will help to dry them after rain or watering. Stake or cage the plant to enhance aeration and drying by the sun.

When rain is not sufficient, watering is necessary. This is best done in the morning when the sun can quickly dry the leaves. Or use a soaker hose around plants to avoid getting water on leaves altogether. Spreading mulch around each plant also prevents disease spores from splashing onto plants.

If, despite these measures, your plant develops one of these diseases, make sure to remove the diseased plants or parts of plants while leaves are dry to avoid spreading the fungus to other plants. Dispose of the plant material and do not compost it.

You can use a fungicide (always read and follow directions) to prevent infection in healthy plants but it will not cure a diseased plant. The fungus can overwinter in your garden so make sure to remove all plant debris at the end of the season.

You can prevent infections season to season by rotating crops in your garden every two to four years if possible. This means changing the location of or staying away from the entire tomato (nightshade) family which includes peppers, eggplants and potatoes.

I look forward to having homegrown tomatoes each year for my favorite BLT so let’s hope for a great crop this summer!

Have questions for the University of Illinois Extension Master Gardeners? You can call, email, or visit during the growing season. Learn more about connecting with the Kendall County Master Gardener Help Desk at, or call or visit during office hours: Monday, Wednesday, and Friday from 9 a.m. to 12:30 p.m. at 630-553-5823 or at 7775-B IL Route 47, Yorkville.