I have had several calls this past week about issues with tomatoes. Many of the issues are disease related, while some are insect damage or nutritional problems.
I visited with a homeowner early this week and saw some of the leaves rolling up, which is common on tomatoes that have a heavy fruit set. So, from the large volume of calls, I thought it would be appropriate to talk about some of the common things we need to look for and manage during this time.
A fungus causes Fusarium wilt. It blocks the water conducting tissues in the plant. The leaves yellow and wilt, often starting at the bottom of the plant. This disease can affect just one side or one to several branches of the plant. The plant can die early, producing no fruit. If you cut into the plant, the vascular system (just under the bark) will be brown. Control Fusarium wilt by planting resistant varieties. The ‘F’ after the name, like Celebrity VFN identifies these. Fusarium wilt can survive in the soil. Do not plant tomatoes in infected areas more than once every four years.
Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it does not have time to yellow. To identify bacterial wilt, cut through the stem. Bacteria wilt browns the pith or middle of the stem. On bad infections, the pith may be hollow. Cut a short section of the stem and suspend it in a clear glass of water. You can often see a milky ooze streaming out of the bottom of the cut stem.
There are no controls or resistant varieties for bacterial wilt. It also attacks peppers, potatoes and eggplant. Carefully dig out infected plants and soil and discard. Do not plant any of these vegetables in this area for at least four years.
Blossom-end rot (BER) appears as a dry, leathery spot on the blossom end of tomatoes. It can also affect peppers and watermelons. BER is caused by lack of calcium in the blossom end of the fruit. By the time the tomato reaches the size of a nickel it has most of the calcium that it will ever have. This is why we need to prevent blossom end rot early. Inadequate water supply, low pH or low soil calcium levels can cause this problem. Find and correct these problems.
Once a plant has BER, it is hard to control. Calcium is best taken up by the roots so sprays are not very effective. Control and prevent BER by:
• Water the plants well and let the soil dry between waterings. A sample watering schedule is three-quarter inch twice a week if there is no rain.
• Apply a two-to-three-inch mulch around the plant. Do not heavily prune the plant.
• Soil sample and lime and fertilize as needed. Avoid large applications of high nitrogen fertilizers when fruit are small.
• Add gypsum (calcium sulfate) or lime to the soil at planting. Mix a cup in each planting hole or use one pound per 100 square feet. You can apply this once you see the problem but these treatments work slowly. Plants often appear to grow out of the problem as conditions improve.
Leafrolling occurs when the plant has set a heavy load of fruit and the light intensity is high. It can be caused by wet soils. The condition is harmless and should not hurt final production. Prune less heavily and plant in a well-drained area.
Fruit cracking is due to rapid growth after periods of slow growth. Rain after drought and heavy fertilization can cause fruit cracking. Harvest fruits after they begin to turn red but before they crack. Follow the watering practices we have discussed and look for cracking resistant varieties.
Catfacing is caused by cool temperatures at time of pollination. The fruit is deformed with “zippers” on the skin. The fruit can have lobes, tear drops or several blossom scars. Plant resistant varieties, plant later, or use row covers to increase the temperature on cool days and nights. The large beefsteak varieties appear to be more susceptible. The fruit is still edible.
Sun scald appears as a white blistered area on the top of the tomato. Do not prune heavily and maintain nutrition and pest control so as to provide a good leafy cover for the fruits. Be careful not to confuse this with Blossom End Rot.
For additional questions contact Effingham County Extension Agent Sam Ingram at 754-8040 or firstname.lastname@example.org.