Late blight can wipe out your backyard garden. Here’s how to spot it and stop it before it takes hold.
Three years ago, I had grand plans. I planted over 300 tomato seeds, spending hours watering, turning, and transplanting them. I dug 300 holes—one for each plant—and carefully placed them in the ground.
I put in even more time pinching off suckers and tying the plants to stakes with twine. They grew beautifully, loaded with green tomatoes just waiting to ripen.
Aren’t they gorgeous?
Late blight can be a nightmare for home gardeners. Learn how to fight it organically and protect your crops before it strikes!
Then I spotted it. Black patches on the leaves, fuzzy white growth underneath. We’d battled bacterial spot and early blight before, but this was different. As I walked through the garden, I found more plants with blackened stems and fruit that looked bruised.
I had a sinking feeling but snapped photos to send to my husband and turned to Google. My heart dropped.
It was late blight.
I was crushed. We dug up every infected plant we could find and sprayed the rest with organic copper fungicide. But one by one, the plants fell. Within a month, every. single. one. was infected. We managed to harvest a few early tomatoes, but our dreams of homemade canned sauce were gone.
I wouldn’t wish that on any gardener! So how can you stop late blight from ruining your garden? First, let’s talk about what it is and how to recognize it.
Signs of Late Blight
Late blight isn’t like other garden diseases. Most just reduce your harvest, but late blight destroys entire plants—and it spreads fast. One infected plant quickly becomes two, then three, and so on.
Technically, late blight is caused by the fungus Phytophthora infestans. It travels on the wind as spores, sometimes over long distances, and attacks tomatoes and potatoes (remember the Irish Potato Famine?). Keep an eye on both crops.
Destroy infected plants completely—no leaves, stems, or roots left in the garden, soil, or compost. We bagged ours in trash bags. The good news? Late blight won’t linger in your soil or on tomato cages, but remove every trace of infected plants.
Cool, wet weather speeds up the disease, creating perfect conditions for it to thrive.
- Leaves are usually hit first, especially lower ones. Look for blackened areas with white, fuzzy fungus underneath.
- Stems develop random black spots, often near joints.
- Fruit shows signs last—green tomatoes turn brown in patches, then completely rot.
Late blight can be devastating. Learn how to protect your garden organically before it strikes!
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How to Prevent Late Blight
An ounce of prevention is worth a pound of cure, right? Here’s how to keep late blight at bay:
- Plant resistant varieties. Some heirlooms and hybrids have natural resistance.
- Give plants space. I crammed mine too close together—bad idea. Proper spacing helps leaves dry faster and improves airflow. (Check my garden spacing guide for recommendations.)
- Water the roots, not the leaves. Wet foliage invites disease. Keep water low to the ground.
- Rotate crops. Don’t plant tomatoes or potatoes in the same spot year after year. Leftover plant matter might harbor spores.
- Solarize soil before planting.
- Spray preventatively. Use organic fungicides like Serenade or copper spray before you see symptoms.
What to Do If Late Blight Hits
In years of gardening in East Tennessee, I never saw late blight. Now in Western North Carolina, it’s not if but when. We live near commercial tomato fields, so spores are everywhere—and without a hot, dry summer, it’s a yearly battle.
If your plants get infected:
- Pull them up immediately. Bag everything and trash it.
- Spray surviving plants with Serenade or copper fungicide.
- Report it to your local extension office. Late blight spreads easily—don’t risk neighbors’ gardens too.
- Don’t quit. Losing a garden hurts, but bounce back! Plant fall crops like greens, beans, or brassicas.
- Plan for next year. Prep soil early, choose disease-resistant varieties, and plant quick-maturing tomatoes to harvest before blight strikes.
My Yearly Gardening Planner keeps everything organized—seed inventory, planting dates, pest issues, and more.
That year, we salvaged hundreds of pounds of green tomatoes, trying to ripen them indoors. Most rotted first.
Despite the heartbreak, we still grow tomatoes every year—we’re just extra cautious now. Have you faced late blight? Share your story in the comments!