After spring planting work is accomplished, many gardeners will fail to realize the importance of staying on top of and controlling disease and insect infestations. Problems can develop very quick (often over night) and taking a proactive approach can help to reduce problems and solve existing ones. A few major fungal problems can occur with tomato plants. These include Septoria leaf spot and Alternaria leaf spot (also known as Early Blight). Both problems start small and spread rapidly through the leaves of the plant.

Symptoms for Septoria Leaf Spot Fungus (Septoria lycopersici)

Septoria Leaf Spot (fungus) is similar to Early Blight and are often misidentified. This fungus is quite common and is a very destructive tomato plant disease. Septoria creates symmetric spots on the leaves starting out as tiny black spots and growing (if left uncontrolled) to larger black spots surrounded by yellowing of the leaves and stems. Defoliation is quite common as the fungus spreads through the leaves, down the stem,  and to the main trunk of the plant. Heavy rain in early spring or over watering of tomato plants provides a breeding ground for the fungus. Defoliation can lead to the sunburn of the fruit and the tomatoes may not mature properly.

Septoria Leaf Spot can be identified by the concentric spots on the plant while the blight varies in size and shape. The plant appears to wither from the bottom up and the plant’s leaves drop off as the fungus works its way up the plant. The best treatment for this type of fungus is to remove all affected foliage from the base of the plant, lay down a bed of organic material such as mulch around the base of the plants, and treat the plants using a fungicide specifically labeled to treat Septoria.The fungicide should be applied every 7 to 10 days.

If you have had a history of Septoria Leaf Spot, be sure to begin treatment of your plants as soon as the first fruit clusters appear. Remove all affected debris from the garden and dispose of  in a plastic bag left in the sun for a few days then place in the yard waste collection from your local sanitation department. Rotate your tomatoes with other plants such as cereals, corn, or legumes each season typically leaving the severely affect areas free from tomatoes and other related plants such as potatoes and eggplants for at least three years.

Septoria Leaf Spot is just one of the many possible problems affecting your tomato plants. Fungus, bacteria, and insects are common and can devastate a crop. Positive identification of your problem is necessary to treat the problem correctly. Take pictures of your plants and compare them with pictures you find on the internet or take them to a local green house to see if the experts can help you to identify your problem.

Treating Your Tomatoes with Fungicides

Many products exist to treat varying forms of fungus on your plants. Make sure to read the label to make sure the suspected fungus on your plants is treated by the fungicide you choose or the product will not be effective. One product found on the market to treat Septoria Leaf Spot is Daconil. This fungicide comes in a ready to use form and you simply spray on the plant to prevent further spread of the disease. You can also spray the ground surrounding the plants to help reduce the affects of the fungus on the plants.

Please feel free to ask questions or advice concerning the care and maintenance of tomato plants. We would love to hear from you.