We get a lot of calls every year from people with gardening questions, and if you have questions I encourage you to continue to contact your local Extension office. Tomatoes are one crop that we get many calls about each year. This article will discuss a few of the more common tomato problems, but keep in mind that many tomato problems are hard to identify in the field and need to be sent to our pathology lab at Auburn or Birmingham. Information on collecting and mailing plant samples can be found on our website or by contacting your local Extension office.
Keep in mind that many tomato problems can be identified from sending pictures to your local Extension office or describing the problem over the phone. We have many publications with pictures and descriptions of tomato diseases that are available on our web site or at the Extension office.
Blossom-end rot is a very common tomato disorder, but can affect many other crops including pepper, watermelon, squash, etc. It is decay usually on the blossom end of fruit caused by a lack of calcium in the plant. The lack of calcium in the plant could be a result of deficient calcium in the soil, but it could also be the result of the roots being too wet or too dry (stress). The best thing to do for blossom-end rot would be to soil test and add the proper nutrients including calcium and maintain the soil pH at 6.0 to 6.5. Mulch the plants and irrigate when needed. I usually do not like the idea of spraying calcium products on the leaves because it is easy to burn the leaves and the plant can not take in the recommended amount of calcium through the leaves. Calcium fertilizers are available and will increase the calcium in the plant by providing it to the roots.
Blossom drop is not a disease but another very common tomato disorder. It is the result on some tomato varieties when daytime temperatures exceed 85oF and nighttime temperatures stay above 72oF. Often times it is the high nighttime temperatures that reduce flowering the most. Plants should start producing again as temperatures become more favorable. Many heat set tomato varieties are available that continue to set fruit in higher temperatures.
Tomato plants can get several viruses, but tomato spotted wilt is usually the most common virus that I see. The plants’ growth rate will become stunted, they will turn a lighter green color, and the leaf veins may have a purplish tint. If fruit develop they will have ringspots and quality will suffer. The disease is commonly spread by a tiny insect called a thrips. Thrips feed on many plants including weeds around the garden/field. Managing thrips by destroying weeds adjacent to the field may help but may not stop the problem. Planting tomato spotted wilt resistant varieties is the best method for managing the disease and many tomato spotted wilt resistant varieties are available.
Fusarium wilt, southern blight, and bacterial wilt are three common wilt diseases of tomatoes. Fusarium wilt enters the plant through the roots and can cause the plant to wilt. It may start with one stem before spreading to the rest of the plant. Cutting into the stem at the base will show a brown discoloration in the vascular system. This fungus may persist in the soil for many years so crop rotations may not help with this disease, but many fusarium wilt resistant tomato varieties are available. Southern blight symptoms include wilting and yellowing of the plant along with a white fungal growth at the plant base. Best management practice includes destroying infected plants and crop rotation. It is advisable not to plant tomatoes or susceptible crops in the tomato family more than once every four years. Bacterial wilt causes plants to wilt and die rapidly without any other symptoms. To check for bacterial wilt a grower can place a cut section of stem in water. If bacterial wilt disease is present, a white milky substance will seep from the stem. A management option is the same four year rotation as for southern blight.
Early blight, late blight, septoria leaf spot, bacterial spot, and bacterial speck are common foliar tomato diseases. Management options include planting disease free seeds or transplants, crop rotation, mulching, and no overhead irrigation. A regular fungicide spray program will help as well. We have information for spraying vegetables at our office if you are interested.
Tomato plants can get many diseases other than the ones mentioned in this article. We have publications at our office and on our website that describe these diseases or disorders in more detail if you are interested. It is sometimes hard to identify diseases from pictures or descriptions and for a positive diagnosis a sample may need to be sent to our lab at Auburn or Birmingham. Information for sending samples can be found on our web site or by visiting your local Extension office. There is a small fee of $10 to $15 for sending samples, but losing a crop is much more expensive.
What can be done to reduce the number of gardening problems? Choose a location with well-drained soil or at least try to avoid low areas that stand in water for extended periods. An area that receives full sun and is close to a water source would also be beneficial. Having more than one garden spot will allow you to grow summer cover crops and aid in crop rotation as well. Growers should soil test to determine the amount of elements that are in the soil in order to determine what elements need to be added. Plant nutrition is a very common problem and one that many overlook. Plant disease resistant seed/plants as much as possible, many problems can be avoided at planting. Amending the soil with organic matter, weed control, mulch, and drip irrigation helps reduce stress on the plants which in turn makes plants healthier. If you have any questions, just give us a call here at the Extension office.
by Dr. Chip East, Regional Extension Agent – Commercial Horticulture