What Is Tomato Blight
There are two types of blight which affect tomatoes; Alternaria (or early blight) and Phytophthora (or late blight). Both of these are fungal pathogens which can cause tomato leaves to suddenly wither, stop growing and die which can eventually kill a plant if not taken care of immediately and properly. Blight can be prevented, however, with proper garden maintenance and care.
Early Blight Symptoms
In the case of early blight, darkened brown and black spots appear on leaves. These spots usually show up on the bottom leaves of a plant first, starting small and eventually enlarging and develop concentric rings. Leaves showing heavy symptoms become dry and eventually die as these rings merge together.
Symptoms can also show up on the stems of plants and usually show as sunken, discolored spots. The stem eventually rots away, leaving all parts of the plant above the affected area to die.
Late Blight Symptoms
Late blight shows up a little differently on tomato plants. This fungal disease first appears as discolored water spots on the lower leaves of a tomato plant. These spots eventually enlarge and can be seen on both sides of a leaf, like rust in roses. The underside of the leaf shows as a fuzzy white growth.
How does Tomato Blight Spread?
Fungal blights are caused by wet leaves in a plant. Most fungus needs a whole 12 hours of moisture to allow spores to germinate. Leaving leaves on a tomato plant wet for a long period of time will encourage the growth of this pathogen.
How To Prevent Tomato Blight
To prevent early and late tomato blight practice the following:
- Never let water splash on the bottom leaves of a plant. Instead of overhead watering, water the soil.
- Water in the early morning so plants can dry off during the day. Watering in the evening encourages moisture to form on the lower leaves of a plant which can cause fungal spores to germinate.
- Make sure plants are spaced properly apart. Also encourage air circulation with proper pruning. This allows leaves to dry off if they chance to get wet.
- When symptoms first appear remove the infected areas immediately and dispose of them.
- DO NOT PUT INFECTED PARTS INTO YOUR COMPOST PILE. Infected leaves and other plant parts added into a compost pile can overwinter in the soil and even on seeds.
- Use a 3-year rotation. Rotate the location of your tomato plants to prevent pests and diseases from previous seasons.
- Foliar sprays of compost tea, or other foliar sprays which encourages beneficial microorganisms, can help prevent diseases.
How To Treat Tomato Blight
Organic tomato blight fungicide treatments include spraying potassium bicarbonate (baking soda).