If you grow tomatoes, you may be aware of the three types of tomato blight that can affect your plants. These are Early Blight, Late Blight and Septoria Leaf Spot and all three are fungal diseases spread by spores. The spores need moisture from dew or rain so your plants are more likely to be infected during wet weather and the disease will be much more severe than in dry conditions.
When the first tomatoes appear, watch out for Septoria leaf Spot on the leaves at the base of the plant. While this won’t affect your tomatoes, it will reduce the number of fruit available for harvest and the quality. Due to the major loss of leaves, the tomatoes will be more exposed and there more susceptible to scalding by the sun. The reduce the chance of infection with septoria leaf spot avoid splashing water over the plant and water your tomatoes from the base and try not to work on your plants if wet. It is also important to remember that this form of tomato blights can survive the winter in the refuse from your plants therefore always dispose of infected plants completely far away from the rest of your growing area.
Another form of this disease is Early Blight which usually makes an appearance after a lot of tomatoes have set and again the lower leaves will be first to show signs. This will appear as spots that develop on the leaves ranging from dark brown to black in color which will gradually take shape as a bull’s eye. The leaves around this spot will turn yellow and then drop off but this blight also attacks the stem and on occasion the tomatoes too. If the tomatoes are affected, you will see large black spots appear close to the stem end and these will drop off the plant before they have matured. This particular fungus usually happens late in the growing season and can also be found in refuse from infected plants left over from the winter.
When the weather is damp and rainy, with hot days and cooler nights, Late Blight can occur. Its symptoms spread from the edge of the leaves inwards and appear as dark green spots that are almost black in color and if the weather is particularly wet you may notice a white growth around the outer rim of the spots. The tomatoes will also have blight spots and this form of the fungus can spread very quickly to infect your whole plant. In order to prevent this, there are ways to reduce the chances of infection by blight.
- Don’t use a sprinkler to water your plants as water splashing will spread the spores that cause the disease so bottom watering is recommended instead.
- Eliminate any of the lower leaves that have come in contact with the ground.
- Take of any leaves that look discolored or show signs of infection as they may be holding spores which will cause the infection.
- Always rotate your planting spot and only plant your tomatoes in the same place every three to four years, space permitting.
- Dispose of any refuge from the plants including vines and waste from the tomatoes at the end of each growing season.
- Once the garden has been cleared, root-till in the fall.
While fungicides are available which help prevent tomato blight diseases, they will not be effective when the disease starts to spread therefore prevention is better than cure if you apply periodically throughout the season before you see any sign of the disease.