Sauk County Gardener: Be on lookout for these tomato diseases
“Knowledge is knowing a tomato is a fruit. Wisdom is not putting a tomato in a fruit salad.” ~Miles Kington
I had the opportunity to attend the Wisconsin State Fair this past weekend. It’s always been a favorite end-of-summer activity for me as I eat my way through the fair – roasted corn, baked potato and, of course, the glorious State Fair cream puff. I enjoy seeing all of the exhibits, many of them provided by our very talented youth throughout the state. Another one of my favorite areas to visit is the Grand Champion exhibits where the amazing displays of cut flowers, herbs and vegetables grown by Wisconsin gardeners are located. A bonus was listening to gardening expert, author and columnist Melinda Myer speak about ways to create garden fun for everyone. If you have never been to the Wisconsin State Fair, put it on your list for next year.
Of course, after that I had to return to the reality of my own gardens. I continue to harvest a variety of vegetables from my raised garden beds. My tomatoes are fully loaded but are taking their sweet time ripening. I’m getting a few here and there as the weather temps have not been cooperating. The optimal temperature for ripening tomatoes is between 68 and 77 degrees F. When temperatures are above 85 degrees, tomatoes won’t product the pigments, lycopene and carotene, that are responsible for the ripe tomato color.
While you are waiting for the perfect temperatures, keep an eye on your tomato plants for diseases. I did a much better job providing more space between my tomato plants, so I’m only dealing with a few that are developing Septoria leaf spot. The foliage is spotted and the disease usually appears when it’s wet and humid. If you have this, continue to prune out infect leaves and stems to increase air flow. Remember to disinfect your pruners or wash your hands before moving to the next plant. Do not compost the diseased foliage – put it in the trash or bury it. Mulch around the base of the plant if you haven’t already, avoid overhead watering, and control weeds. If these methods don’t work to control the disease, you can use a fungicidal spray for tomatoes every seven to 10 days to protect new leaf growth. Remember to read the label for proper usage.
Early leaf blight is another fungal disease that can affect tomatoes. It causes circular or irregular dark spots surrounded by yellow and starts on the bottom leaves. It thrives in moist, warm temperatures (80 to 90 degrees F) and can cause extreme defoliation resulting in sunscald and reduced production. This too can survive in garden waste for a year or more, so it should not be composted. The best way to manage it is to maintain plant vigor, avoid working around the plants when wet, and remove diseased plants from the garden in the fall. You can also apply fungicides, such as those that include copper, beginning at fruit set and reapplying every seven to 14 days.
Another problem I’m seeing on my volunteer tomatoes is a little blossom end rot. I haven’t been watering them consistently like I was doing with my other tomato plants, so I’m assuming that is the main reason for this problem. You can get blossom end rot in not only tomatoes, but also peppers, watermelon, eggplant, squash and cucumbers. It is a result of a calcium deficiency in the fruit itself. Once the fruit gets blossom end rot, it can’t be saved. These plants need a consistent supply of calcium during the fruit set for the fruit to properly develop. The best way to make this happen and prevent blossom end rot is consistent soil moisture. This can be accomplished by regular watering (drip irrigation system) and mulching to prevent moisture evaporation.
Late blight is another disease to watch for that affects tomatoes and potatoes. It presents itself on the fruit, leaves and stems as brown lesions. The leaf lesions start out small and enlarge to large lesions and blotches, and eventually kill the leaf. The stem can develop dark brown lesions. On the stem, the fruit can have firm brown lesions and a rough/bumpy surface. If detected early, fungicides may help prevent the spread to other plants. However, fungicide is only effective if it’s applied before a plant becomes infected with late blight. If you discover it, the plant should be destroyed by burying or put in the trash.
If you want to learn more about tomatoes, please join the Sauk County Master Gardeners Association, this Saturday, Aug. 28, for the annual Terrific Tomato Tasting. It will be held from 10 to 11 a.m. at the Baraboo Civic Center, 124 Second Ave. Attendees can learn about local gardeners’ successes and/or failures, sample a variety of tomatoes (many are flavorful heirlooms) and vote for their favorites. It’s free and open to the public, so please come join them.
Jeannie Manis is a Wisconsin-certified Sauk County Master Gardener volunteer. If you have any gardening questions, please contact the Extension Sauk County by emailing to tim.ripp@saukcountywi.gov or calling the University of Wisconsin Madison Division of Extension Sauk County office at 608-355-3250.
