Many gardeners are trying their hand at growing tomatoes this season and many of them have some nice tomatoes that will be ready soon. Unsurprisingly, “What’s wrong with my tomatoes?” is a question that I’ve been fielding a lot lately.
Tomato problems may be caused by a myriad of factors, including nutrient deficiencies, diseases, fungi or insects. Fortunately, good cultural control practices can reduce or eliminate many of your tomato troubles. Now is about the time I get calls about blossom end rot. Most say their tomatoes look good, with a healthy vine, but some tomatoes are “turning black and rotting on the bottom end” (opposite the stem).
What those gardeners are describing is blossom end rot, and it is not at all uncommon in tomatoes. It is a physiological disorder that occurs where there is a calcium deficiency in the fruit. It can be caused by low calcium in the soil or other cultural factors, such as fluctuating soil moisture (either too dry or too wet). Such conditions result in a deficiency in calcium available to the maturing fruit.
It is almost unavoidable in hot conditions, especially with the 100 degree days we had during Memorial Day weekend and are likely to have in the months ahead. But don’t worry – while blossom end rot is bound to occur, it is treatable and cultural practices can be done to reduce its occurrence.
Here are some tips for managing and preventing the occurance of blossom end rot on your prize-winning tomatoes:
1. Apply lime to the soil several months before planting. This will put calcium in the soil well before your plants are in the ground.
2. Avoid use of high nitrogen fertilizers. Too much nitrogen can promote blossom end rot by causing excessive vegetative growth, which can “rob” calcium that would otherwise go to the fruit.
3. Remove tomatoes showing symptoms of blossom end rot. While they can still be eaten if the spot is small, their removal may help the plant reallocate nutrients to produce new healthy fruit.
4. Water regularly. Watering deeply two or three times a week is better than frequent light watering. Note, if your tomatoes are in pots or buckets, they may not be able to hold that much water and may need it more frequently.
5. Don’t overwater! Too much water can be just as bad as not enough. Make sure the plants aren’t water-logged. Remember, extreme fluctuations in soil moisture can cause an increase in blossom end rot.
6. Many people have tried 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.
Another common issue gardeners run into with their tomatoes is the fungal disease Alternaria leaf spot, commonly known as early blight. Anyone who has attempted to grow their own tomatoes should be familiar with this disease. As the weather becomes warmer and more humid, the disease will move up the plant, infecting a major part of the tomato plant’s foliage. By the end of the summer you may actually have single stalks and just a few green leaves at the top of your tomato plants.
If you’re new to gardening then you may not be familiar with the various tomato problems that occur throughout the season. So, if your plants look like they are in a slump, especially this time of year, then it’s probably because they are infected with early blight. Heirlooms are particularly susceptible.
Signs to look for include brown to black, target-like spots on older leaves. Leaves will eventually turn yellow and wither. If severe, the fungus also attacks stems and fruit. Affected leaves may turn yellow, then drop, leaving the fruit exposed to sunburn.
Sanitation, a cultural control method, is the best measure you can take against this disease. Remove all diseased plant tissue on the plants and on the ground, as the fungus overwinters on leaf debris. Do not plant tomatoes in the same place year after year. Improve air circulation by spacing plants further apart so their leaves can dry more quickly. Avoid overhead irrigation.
Tomato plants infected with early blight disease often produce fewer flowers, thus, much less fruit as well. To control early blight, at the first indication of early blight disease on the foliage, pick those leaves off and destroy them. Keep your tomato plants mulched well to prevent disease spores from splashing from the ground onto the lower foliage.
If the disease persists, then you may want to consider using a fungicide. Just remember, fungicides are preventative, not curative. Just as you wouldn’t run to the doctor to get a flu shot after being diagnosed with it, spraying a severely infected plant will not save it from the disease. To get the most out of your fungicide application, the best practice is to remove and dispose of any infected foliage as soon as it’s detected, and then spray the plants with a recommended garden fungicide.
For more information on growing tomatoes, contact the Liberty County Extension office at 912-876-2133 or firstname.lastname@example.org.