How to Treat and Prevent Early Blight on Tomatoes

One very common problem that may appear on your tomato plants is early blight (Alternaria solani). Early blight can be identified through brown spots on the lower leaves of your tomato plants. The brown spots resemble a “bull’s eye” pattern of circles. It may even remind you of tree rings.

Early blight is a fungal disease that can overwinter in plant material, compost, and the soil and when it rains or irrigation water splashes up on the plants and allows the blight to infect the plants.

How do You Treat Early Blight on Tomatoes?

Good pruning practices are the number one way to reduce and prevent it’s spread to healthy areas of your tomatoes. There are 3 things you can do when pruning to make your plants less hospitable for fungal diseases like blight:

1. Clear the lower area of your plant of branches and leaves. I talk in detail about doing this in this post: Pruning the Lower Limbs off of Tomato Plants. Essentially you open the lower are of the plant up so that it can dry out after watering and you make the environment less hospitable for fungal diseases.
2. Prune out the canopy of the plant and limit the suckers to help improve airflow. If you have too many branches it will slow the evaporation of water that fungal diseases need to grow.
3. Prune off the suckers. The suckers can create too much foliage which can contribute to poor air flow. As an added benefit reducing the suckers will help to make for larger tomatoes!

Mulch to Prevent Fungal Diseases

Fungus diseases can persist in the soil so adding a protective layer of mulch can help prevent the introduction of the fungus on your leaves. When it rains or you water the droplets can bounce back on the leaves and introduce the diseases from the soil. A layer of mulch will interrupt that process! Straw, woodchips, pine needles, leaves, and grass clippings are all good mulches to use around your tomatoes.

Use a Fungicide

Since blight is caused by a fungal disease you need to use a spray that can help prevent it’s spread to other parts of the plant.

You can make a Baking Soda and Water Solution that will change the alkalinity of the leaf surface. Fungal diseases like an environment on the acidic side and the basking soda water solution changes to a more basic pH.

DIY Fungal Treatment Recipe: 1TBS Baking Soda in a Gallon of water with a drop of dish detergent to help it mix

Neem Oil can also be effective at a variety of issues including some fungal diseases. It may help as a preventative measure for fungal issues. Be careful with it as it is an oil and should not be applied in the heat of the day. The best time to apply Neem Oil is in the evening where it work over night. Oils typically are used to control insects but can help prevent fungal spread by preventing the insects from spreading the disease.

Copper based fungicides can be the most effective at preventing the spread of blight and other disease issues including bacterial diseases. Copper sulfate should be applied every two weeks and after a rain to help prevent the spread. Be sure to read the label and follow their specific recommendations as each fungicide may be formulated differently.

More on Blight and Leaf Spot

A Word of Warning: Do Not Compost

Don’t compost leaves that have been infected with fungal diseases. The diseases can persist in the compost and when you use it the compost will spread the fungal issues to other plants. Throw away the infected leaves or let them dry and burn them in a firepit. Then you can use the ashes in your compost!

A Couple Fungicide Products that May Help Against Blight and Leaf Spot

Below are a couple products you can use that may help in your garden to prevent and treat fungal diseases. The links below are Amazon Affiliate links.