There is nothing quite like going out to your garden for a truly “vine-ripe” tomato. Some years it seems to take forever to bite into that first homegrown beauty. There are several tomato diseases that gardeners must battle to have productive tomatoes — the most frequent one being early blight.
Early blight is a disease caused by a fungus which survives in the soil as spores from year to year. The disease usually starts when soil, which contains spores, gets splashed onto the lower leaves. After the disease develops on these leaves, more spores are produced which get splashed further up the plant. In extreme cases, the fruit and the stems can become infected.
The initial symptoms are irregular brown spots on the leaves that have darker concentric rings within the diseased areas. Later, many spots may grow together to blight the entire leaf. This disease can be greatly reduced by using newspaper topped with a thin layer of mulch around the plants to keep soil with spores from being splashed onto the leaves. You’ll find that wetting the paper as you lay it down will keep a breeze from blowing it away until you add the mulch.
Drip versus overhead irrigation will minimize soil splash as well. If the disease occurs, remove affected leaves. Even when you see no symptoms, removing lower leaves and suckers from the tomato plants as they grow will help with air circulation and drying which helps prevent infection. Tomato cages can often exacerbate the problem due to forcing crowded growth with low air circulation. You might want to use stakes, trellises or the Florida Weave system instead of cages.
Always remove diseased plant parts to prevent the spread and be sure to remove the plants at the end of the season when you have picked your last tomato. As with any diseases, rotating your tomatoes to other areas of the garden each year can reduce the chances of the disease. Be aware that in crop rotations, you do not want to plant tomatoes where their close relatives, peppers, eggplants or potatoes were grown the previous year.
For information on this and other tomato diseases see the fact sheet HGIC 2217 Tomato Diseases & Disorders.