Although typically very easy to grow, tomatoes are prone to some problems. According to Rhonda Ferree, extension educator in horticulture, University of Illinois Extension offices are receiving many questions right now concerning the most popular homegrown vegetable - tomatoes. This year's cool, wet conditions have results in increased tomato disease.
Many tomato growers are experiencing leaf diseases this year such as septoria leaf spot and early blight. These produce small spots on the lower leaves. In wet weather conditions, they can defoliate plants from the bottom up. When leaves are lost, the tomato fruit is exposed to sunscald (whitish areas on the fruit). To manage these diseases keep all ripe fruit picked off plants, improve air circulation in the garden, mulch to avoid fruit rots, and remove tomatoes and vines at the end of the season. University of Illinois Extension also suggest using a two- to three-year crop rotation to reduce losses from these diseases.
There are fungicides labeled for use on tomatoes to control tomato leaf diseases. They are sold under many different trade names, so read the label carefully to be sure you purchase the right product. Look for a product that lists tomatoes and says it controls the diseases mentioned. Read and follow all directions carefully. These fungicides often need repeated applications at certain intervals to work properly. Most importantly, follow any harvest intervals to be sure the produce is safe when you eat it.
Later blossom-end rot may become a problem for some growers. Blossom-end rot appears as brown or black areas at the blossom-end of the maturing fruit. Tomato, pepper, summer squash, and other cucurbit crops may show this problem. This is not a disease, but rather results from low calcium levels in the plant. This usually occurs during dry periods when the plant grows slower and takes up fewer nutrients from the soil. The best way to manage this is to maintain even and adequate soil moisture.