The most commonly grown crop in central Indiana gardens is the tomato. They do well in our climate; however, as any experienced grower knows, they are also susceptible to several diseases.
About this time of year two common fungal leaf-spot diseases often appear on tomato plants. Septoria leaf spot and early blight are both characterized by brown spots on the leaves.
Septoria leaf spot usually appears earlier in the season than early blight and produces small dark spots. Spots made by early blight are much larger and often have a distorted "target" pattern of concentric circles. Heavily infected leaves eventually turn yellow and drop. Older leaves are more susceptible than younger ones, so these diseases often start at the bottom of the plant and work up.
This is the type of year where both of these diseases can become prevalent. The reason is that each of the pathogens responsible survive in the soil and old plant material. When we experience vigorous rainfall, such as we have had several times over the past few weeks, soil particles carrying the fungus are splashed onto the lower leaves of the plants. The warm, humid weather we've been having is also very good for the development of these diseases.
These diseases can spread rapidly, so it's important to scout for symptoms. If you find evidence of them, fungicides can be effective in preventing their spread. Be sure to apply fungicide to both upper and lower leaf surfaces, and reapply if rainfall removes it.
See Wednesday's Times Sentinel for the full story.