I have recently received numerous calls about problems with tomato plants. This time of the year we typically see issues start to arise in our flourishing gardens. Two of the most common problems are leaf spots and blossom end rot.
There are three leaf spot diseases commonly found on garden tomatoes: Septoria leaf spot, early blight and bacterial spot. In the early stages they are difficult to tell apart. Most home garden tomatoes do not need to be treated with a fungicide. Tomato plants can tolerate high levels of leaf loss from leaf spot diseases without affecting the number of tomatoes produced by the plant. Use cultural control practices like staking and mulching plants, and pinching off infected leaves to keep leaf spot diseases in check. Below are some cultural options to help.
Pinch off leaves with leaf spots and destroy them. It is okay to remove up to a third of the plant’s leaves if you catch the disease early. Cover the soil below the tomato plants with mulch. This will reduce the ability of diseases in the soil to splash onto the lower leaves. Water the soil not the leaves. The fungi and bacteria that cause leaf blight need moisture on the leaves to start infections, but tomatoes only take up water through their roots. Keep the water in the soil where the plant can get it. Make sure air circulates well around plants. Providing good air movement around the plants by staking or caging tomatoes, pulling weeds, and spacing plants far apart will allow leaves to dry quickly. Rotate crops. Allow two years to pass before planting tomatoes or peppers in the same location. Do not save seed from infected plants.
The other common problem that I see is blossom-end rot. A water-soaked, blackened spot at the blossom end of tomato fruits is the classic symptom of blossom-end rot. Blossom-end rot is caused by insufficient calcium in the tissue of the tomato. Calcium is taken up into the plant through the roots, however, it settles in one part of the plant. This means that the rot can occur even when there is an ample supply of calcium in the soil, stems or leaves.
Don’t worry if you already have tomatoes suffering from blossom end rot, you can still save them and make plans to prevent it from happening again. Applying lime to the soil several months before planting can help prevent blossom end rot. This will put the needed calcium in the soil. Avoid excessive use of nitrogen fertilizers. This can promote blossom end rot by causing excessive vegetative growth on the foliage, which can “rob” calcium that would otherwise go to the fruit. Remove any tomatoes that begin to show symptoms of blossom end rot. This may help the plant to produce subsequent healthy fruit. Keep the tomato plants watered regularly. Tomato plants need about an inch of water per week to stay healthy. Watering deeply once or twice a week is better than light, frequent watering. However, if your tomatoes are in pots or buckets, they may not be able to hold that much water and may need it more frequently. Overwatering, though, can be just as bad. Make sure that the plants aren’t water-logged. Extreme fluctuations in soil moisture can cause an increase in blossom end rot.
Many people try foliar calcium sprays such as “Blossom End Rot Stop”. These treatments are only short-term fixes and often work poorly because of poor absorption and movement to the fruit area where it is needed. They may help some, but don’t rely solely on them to prevent blossom end rot.
If you need more information, please contact the Madison County Extension office at 706-795-2281 or firstname.lastname@example.org.