Early blight is a fungal disease, and for the home gardener, mass application of fungicides is not practical or advised. Your best option is to apply some Integrated Pest Management principles to limit the fungus’ spread and survival.
Prevention and Monitoring
Early blight is common in tomato gardens. While it may be impossible to prevent it completely, several measures can limit the spread and intensity of early blight.
- Closely inspect any transplants you purchase and bring home. If starting plants from seed, disinfect your containers and tools to kill any potential fungus from the previous season.
- Alternaria are soil-borne fungi, so cleaning your equipment is essential. Snippers, cultivators, shovels, trowels, and any tool used on your tomatoes, potatoes, eggplants, and peppers should be disinfected before moving to another area of the garden.
- Give your tools a quick scrub to remove soil, then dip or spray them with a mild bleach solution.
Choose Tolerant/Resistant Plants
Some tomato varieties exhibit more tolerance to early blight. Unfortunately, this tolerance doesn’t mean complete immunity, but rather that the tomato will “shrug off” and be less affected by the fungus.
Many hybrids and even a few heirloom varieties are available that are less susceptible to Alternaria fungi and blight.
Treatments for Early Blight
Early blight cannot be cured, and cultural methods such as those below are the most effective for the home gardener. Fungicidal treatments for early blight are costly, environmentally damaging, labor-intensive, and thus not practical.
Keep your plants growing vigorously
Fertile, rich soil and lots of sunlight can go a long way to helping tomatoes (and potatoes, peppers, and eggplants) keep marching when early blight starts to show up.
Compost will help your tomatoes to thrive, without the lack of fruiting that too much artificial fertilizer can cause.
Irrigate from below
If you irrigate your garden, try to avoid overhead systems for your tomatoes. Alternaria thrive in wet, humid conditions. The combination of damp foliage and soil splash from overhead sprinklers can worsen a fungus problem.
Use drip irrigation or, if you water by hand, take care to water at the base of the plant and not from up high.
Mulch, mulch, mulch
Mulch is your friend. From weed suppression to soil protection and eventual breakdown into the soil’s organic matter, mulch is hard to beat. In the case of early blight, mulching reduces soil splash from rain or irrigation. It provides a barrier to fungus movement from the soil to the lower leaves.
Prune your tomatoes
Keeping the lower leaves from touching the soil, and promoting airflow through the plant, especially near the ground, can significantly reduce the likelihood of many tomato diseases becoming established. Remove those bottom leaves that aren’t doing much, and let in some fresh air.
Remove infected tissues early
Leaves showing signs of early blight should be pruned off and disposed of. Bury them deeply or burn them. Slowing the progression of the fungi can provide the plant an edge to keep growing up top and have time to give a batch of tasty tomatoes.
Removing the entire plant in the fall after your harvest will eliminate a significant spore source for next spring. Spores can overwinter in the dead vegetation they infect.
Rotation is important
For early blight, rotating where you grow tomatoes and related crops can provide a considerable advantage to your plants.
Alternaria fungi overwinter in the soil, so grow something from a different plant family for two years before returning tomatoes, potatoes, or other Solanaceae to that plot.