Hot weather makes gardens grow. Hot, wet weather makes diseased gardens. And if any vegetable plant is going to contract a disease it is going to be your tomatoes. Leaf spots, blights, wilts, and viruses can end your tomato sandwich season early. Even if they do not kill the plant they defoliate the plant which reduces the productivity.
Sudden wilting with or without yellow leaves usually means the worst; one of the dreaded wilt diseases for which there is no cure. Make sure you move the area where you plant tomatoes next year and start with resistant plants that have “VFN” printed on the plant tag. This will tell you the plants are at least partially resistant to Verticillium and Fusarium wilt diseases. If you see tomato plants yellow then wilt, or just wilt it is a good idea to pull up the infected plants and remove them from your garden. Slight wilting during extremely hot, dry periods is normal under heavy fruit load, but plants should recover overnight.
Viruses often cause deformed leaves, stunted growth, speckled, spotted or streaked fruit and leaves. Viruses are typically caused by insects and there is no cure for this type of plant disease. In addition to preventing insect attacks, do not work in the garden when it is wet and avoid using tobacco before or during your work in the garden. Tomato spotted wilt virus, cucumber mosaic virus, tobacco mosaic virus and double streak virus are common diseases in Georgia. Weed killers sprayed on lawns sometimes will drift into the garden and create damage similar to viruses so use extreme caution when spraying weed killers near your vegetable garden.
Leaf spots, specks, and blights are bad because they defoliate plants but they do not normally kill your tomato plants. Practice good sanitation by deep turning areas where tomatoes have been grown, only water in the morning if needed, and space plants properly to aid in leaf drying. With the best of practices your plants can still suffer from this group of minor diseases if we get showers every afternoon. As leaf spots and blights appear, try using one of the many fungicides such as Daconil, mancozeb or copper products to help new leaves from getting affected.
In addition to wilts, viruses, leaf spots and blights; vegetables can also be affected by other calamities. Over fertilization with nitrogen, or sulfur and other micro nutrients can create burn on plants. Take a soil sample to determine accurate nutrients needs. Over fertilization can also make plants stay vegetative and prevent fruit / seed production. Too much shade or the lack of direct sunlight can limit the ability of the plant to produce adequately. When blights or leaf spots do defoliate your plant hot sunlight can create white spots or sunscald, not a disease but still a blemish can that make the fruit look unsightly. Another common problem with tomatoes is blossom end rot. The symptoms of blossom end rot appear just like the name; dark brown to black rotting on the bottom of tomatoes. To prevent this condition, add a handful of dolomitic lime in the planting hole of each tomato or pepper plant, mulch the plants with straw or leaves and make sure they have plenty of moisture. Once the condition starts, pick off all the affected fruit, add mulch to your plants, and spray with a commercial product called “Stop Rot” (calcium chloride).
Britt West is the extension agent for Barrow County. You can reach him at firstname.lastname@example.org.