Fighting Late Blight Without Chemicals

July 27, 2009 at 8:53 pm 2 comments

Tomato Alert: Late Blight is hitting tomato plants across the country with apocalyptic force, wiping out entire tomato fields in as little as 5 days.

What’s equally as scary are the “organic” and synthetic pesticides people are spraying to reduce the likelihood of blight. Luckily, there are non-chemical methods you can make at home to keep you, and your tomato plants safer this summer.

Late Blight

late_blight_tomato_fruit1x500(courtesy of, and thankfully not on my plants yet)

Usually seen in mid-September, the late blight epidemic was brought on early this year with the cool, wet season we’ve had. The disease thrives on damp weather, and has been spotted in every state along the East Coast. A recent  New York Times article about late blight reported that Chef/Farmer Dan Barber lost half of his entire tomato crop this year already, and others are spraying heavy duty synthetic fungicides to keep the blight at bay. Even the copper sprays that are supposed to be the alternative “organic” treatment are highly toxic to birds, kill earthworms, and have  caused liver disease in vineyard workers in as little as 3  years of spraying.  Here’s a scary report from Cornell covering all of the negative effects of copper sulphate.

So, what can you do to fight blight organically and safely?

Make and Apply Compost Tea

Making compost tea is so simple—-just put a gallon of organic compost in a five gallon bucket, and fill with water. Let sit for 5 days and stir often (it’ll look you’re brewing a big cup of coffee for your garden). Then dilute, and put in a sprayer and apply. You can also buy compost tea online.

Apply to your plants several times each week and after every rainfall. The beneficial microorganisms in compost tea act as a fungicide that one German Study showed to be almost as effective as metalaxyl in treating blight.

Use A Milk Spray

Milk is a natural fungicide, and although I only found one study supporting the use of milk for fighting fungal diseases, there are tons of messages in newsgroups and forums talking about how great milk is for killing spores and helping tomatoes build up an immunity to fungal diseases.  So, give it a try—mix one part milk to two parts water and spray directly on your plants every week.

Act Now

The best time to start protecting your plants from late blight is 2 to 4 weeks before they show signs.

Water Carefully

Blight spreads through dampness, so water your plants only at the base, and in the morning.

Apply Your Organic Spray Frequently, and Every Time it Rains

The synthetic sprays used by commercial farmers are translaminars, meaning they don’t wash off the plant, and only have to be reapplied every three weeks or so. While effective, these are seriously toxic chemical cocktails that are  absorbed by your tomato plants  (which to me kind of defeats the purpose of growing vegetables to be healthier if they are filled with chemicals). So, every time it rains, retreat your plants with compost tea and milk spray.

Check Your Plants

Late Blight starts at the stem, and spreads to the leaves of your plant. Check often to look for the first signs of blight.


Remove Plants with Blight

If your plants get the dreaded B word, they gotta leave the garden immediately (I know, it’s so sad, but for the best). Spores spread quickly, so throw the plant in the trash bags—do not compost the plant or it will breed more blight. Then keep spraying with compost tea and/ or milk spray  and hope the rest of the plants stay safe.

Lastly,  Don’t Purchase Plants from Big Box Stores

Although the weather conditions were oh-too-perfect for blight, infectious plants being sent to big box stores across the country didn’t help matters. An Alabama-based distributor called Bonnie Plants distributed diseased plants to chain garden centers across the Northeast, which were then sold to home gardeners, helping spread the disease quickly. Stick with your locally-owned nursery run by knowledgeable gardeners, and only purchase healthy looking plants with no signs of blight or leaf damage.


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Heirloom Varieties it’s here

2 Comments Add your own

  • 1. Frank Wikle  |  August 5, 2009 at 9:22 am

    We believe 3 or 4 of our plants have blight. We saw a few leaves on one plant with dry top spots and powdery mould under the spot on the leaf. No pictures showed this start. Leaves and stem then dries and dies. All visibly affected plants come out tomorrow. Our plants were grown by us from Heritage seeds ( non hybrid seeds), but 3 or 4 seperate cherry and grape tomato plants were bought from a local supply (hybrid). We were unaware of this blight until after we planted. It only stopped rainingin the last 2 days. Two non hybrid squash plants are going yellow and dieing from I believe to much water. All very sad considering the work we did. Other crops O.K. Sincerely, Frank W.

  • […] is this article about compost tea and milk as organic controls. Fighting Late Blight Without Chemicals __________________ "Orinoco was a fat and lazy […]

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