Tomato Producers Be Wary of Fall Diseases

Clint Thompson Disease, Florida, Tomatoes, Top Posts

By Clint Thompson

Tomato season is here for producers in Florida. Diseases like bacterial leaf spot and target spot should be on the mind of growers preparing their fungicide programs, says Josh Freeman, University of Florida/IFAS Associate Professor in Horticultural Science.

Stem lesions on tomato caused by X. perforans.
Credit: Mathews Paret, UF/IFAS

“In the fall season we really worry about bacterial leaf spot getting established early just because we’re in a period of hot, wet weather. It’s not as bad as it can be at the end of the spring crop. You don’t have a ton of canopy. That’s early in the season,” Freeman said.

What is Bacterial Leaf Spot?

Bacterial spot is present wherever tomatoes are produced and is one of the crop’s most devastating diseases, according to UF/IFAS. Weather conditions like high temperatures, high humidity and rain, favor the disease’s development. Symptoms include dark brown to black spots on the leaves and stems. Leaf lesions start out as circular and water-soaked but turn dark brown to black with a wet or greasy appearance.

“We really don’t want to get leaf spot established early. Our weather tends to get more favorable in the fall as long as we don’t get tropical moisture. By the time we get to September, we start drying down,” Freeman added. “So, it’s just trying to get through this early season without getting bacterial leaf spot established in a big way in tomatoes.”

The other disease concern is target spot. UF/IFAS reports that lesions can appear on the roots, stems, leaves and most importantly, the fruit. That can lead to a marketability problem.

“Fall tends to be a target spot problem. As the weather cools and we get a really big canopy development moving towards harvest and September and October, we worry about target spot. That can be on the fruit. That’s a post-harvest packing problem,” Freeman said.

Growers have chemical options that work effectively. Actigard from Syngenta, is a plant defense inducer. It helps protect tomato plants from diseases. It helps kickstart the plant’s immune response. Other producers will use a combination of copper and Manzate to manage bacterial spot.