what can i do to my tomato garden to combat the early blight that i have been...

Asked January 17, 2013, 12:53 PM EST

what can i do to my tomato garden to combat the early blight that i have been having the last four years ?

Hamilton County Ohio

1 Response

Early Blight is a fungus called Alternaria Solani. It can infect other crops in the garden as well as your tomatoes. The best way to prevent damage from Early Blight is to make your garden less hospitable to the fungus and its spores. The disease is spread through spores and it needs moisture and warmth for this process to begin.

The disease takes hold on the bottom leaves of tomatoes, typical when fruit first sets. It starts out as tiny brown spots on lower leaves. The brown spots might be hard to see. The spots turn yellow, grow and spread. The yellow spots might have a light brown/black/gray center. The discolored center looks like dried leaf surrounded by a yellow ring.

The disease will travel up your plant. You will notice brown dots on the tomatoes. Eventually, the leaves die and drop off, leaving your fruit exposed to sun scalding. The plants weaken and often die or stop producing.

How is Early Blight Spread?
As mention it is a fungus. When the fungus gets wet, spores are released. The spores spread the fungus. The fungus is spread by splashing water, human contact, wind and even insects. The spores can travel distances through hands, tools, insects and wind.

Early Blight needs warm wet weather to spread and grow. If you have warm weather and moisture, your garden is at risk. Early Blight, once established in your garden, can over winter in your garden on debris and weeds.

Don't let it over winter

You can't vacuum up the spores unfortunately. At the end of the season throw away, don't compost, all infected debris and surrounding debris. It is also important to pull up all the weeds in the beds as they take over in the Fall and early Winter period. Spores can over winter on debris and weed hosts. You want to reduce the number of spores laying around in wait.

Turn the soil in mid Winter
The spores aren't super spores. Burying them into the earth helps remove them.

Create a soil barrier (mulch)
Since Early Blight doesn't come right away, you have time to mulch and create a soil barrier. You can use newspaper, plastic, grass clipping, etc. You want to create a splash barrier. Rain drops and overhead watering, splash soil on to the tomato plants. That is one way to infect your plant. Seal the soil and you reduce the chances of spores finding your plant.
Water from the bottom not the top
The spores need moisture. Watering from the bottom prevents splashing as mentioned above, splashing is bad. Watering from the top of your plant makes for wet moist leaves and it creates a temporary humid micro-climate. The moisture allows the fungus to produce spores. Don't water in the evening—night-time watering lets the moisture sit all night.

Air circulation, plant staking and no touching
Air circulation allows the wind to blow through your plants. This allows the timely drying of leaves and it helps break up micro climates. If your plants are packed too tightly together, they themselves become barriers to drying. Staking your plants to poles and using cages helps them grow upright and it creates gaps between the tomato plants. You want to wind and sun to reach through and around your plants. Moisture is needed for Early Blight to spread. Staking and caging also keeps each plant from touching. The tomatoes should be planted with enough distance that only minor pruning is needed to keep them from touching each other.

Remove 2 feet of bottom leaves and prune your plants
Early Blight grabs hold on the bottom leaves first. I mentioned soil barriers and watering from the bottom of the plants to prevent splashing. The next step is to create a 2 foot space between the garden soil or mulch and the first leaves of the tomato plant. Prune the bottom leaves, up you plant over time as it grows, to about an 18 to 24 inch barrier gap. If the spores can't splash upwards and reach the leaves, they can't take hold. The stem usually isn't a place for the spores, though it can be. If you have large plants, you might consider cutting off some branches to let the sun and wind blow through the main body of your tomato plant.

After the tomatoes set add some nitrogen
A healthy plant tends to fight off the spores. You don't want to add too much nitrogen to your tomatoes before they set fruit. Too much nitrogen before fruiting leads to more leaves and less fruit. The leaves are what the spores want. Once the fruit is set, a one-time nitrogen boost can help strengthen your plant.

Remove infected leaves immediately
A leaf should be completely green. Remove leaves that show signs of disease immediately. Look for brown spots or yellow spots or distress. Keep in mind your hands and tools can spread spores. Take precautions not to spread the spores yourself. You should remove leaves and prune when it is dry and sunny. Wash your tools and hands often.

Spray the plants proactively
There are a lot of products for Early Blight. Whichever product you select, the key is to spray early and regularly.

Rotate your crop
If you have the room, move your tomatoes to plots that are free of Early Blight spores.

Hope this answers your question.

Mary