Controlling Tomato Leaf Diseases

By Growing Produce Staff|July 27, 2011

Many tomato growers are having leaf diseases this year such as septoria leaf spot and early blight, producing small spots on the lower leaves, said Rhonda Ferree, University of Illinois Extension educator in horticulture. “In wet weather conditions, they can defoliate plants from the bottom up. When leaves are lost, the tomato fruit is exposed to sunscald, which results in whitish areas on the fruit. To manage these diseases pick ripe fruit promptly, improve air circulation, mulch to avoid fruit rots, and remove tomatoes and vines at the end of the season.”

University of Illinois Extension also suggests using a two- to three-year crop rotation to reduce losses from these diseases.

Ferree said there are fungicides labeled for use on tomatoes to control tomato leaf diseases. “Read the label carefully to be sure you purchase the right product,” she said. “Look for a product that specifically lists that it controls tomato diseases and follow the 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 in the season, 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,” Ferree said. “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.”

For more information on tomato diseases or other horticultural issues, go to www.extension.illinois.edu.