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Master Gardener: Preventing disease in your garden before it strikes

Master Gardener: Preventing disease in your garden before it strikes


Be aware of how your garden practices might be contributing to plant disease. 

Bill Sevier/for the Tulsa World

It seems like there is always something wrong in my garden. If it’s not insects, it’s some sort of disease. What am I doing wrong? JK

It can seem like that sometimes, but let’s talk a little bit about disease prevention rather than just how to deal with disease once it happens.

Resistant plants and seeds

If you start your vegetables from seeds, purchase disease-resistant seeds. If you are like most people, you will say, “How the heck do I do that?” Well, most vegetables have varieties that are more disease resistant than others. Heirlooms (for example) are typically traditional cultivars that have been passed down from generation to generation that remain true to their heritage. As such, they can be more susceptible to disease because they do not have the advantage of having disease resistance bred into them via hybridization. Hybrids are not GMOs; they are varieties that have been cross-pollinated with other varieties to either increase production, increase disease resistance or both. For example, seed packets for tomatoes indicate their disease resistance with the letters V, F and N. Seeds with those disease-resistance indicators would be naturally resistant to Verticillium Wilt, Fusarium Wilt and Nematodes. So right from the start, you are ahead.

Also, try to purchase healthy plants. As gardeners, we all know that the bargain table with the sickly looking plants can be tempting. But try to remember these plants are there for a reason. The reason might be disease. If you can’t resist (and many of us can’t), try to keep them away from your other plants until you nurse them back to health.

Crop rotation

If you plant tomatoes in the same spot every year, disease pathogens can build up in the soil, becoming a bigger problem each year. To counteract this, you can rotate your crops. Some people rotate every year, but for sure, it’s good practice to rotate at least every three years. But here is the trick; you need to learn about the vegetable families because vegetables in the same family are usually susceptible to the same diseases and you might be surprised by who is in the same vegetable family. Tomatoes are in the solanaceous family, so are potatoes, eggplant and peppers. So if you are going to rotate your crops, don’t plant potatoes where the tomatoes were. Brassicas include broccoli, cauliflower, Brussels sprouts, kale, radishes, etc. Legumes include the bean family. And the others kind of make sense. So rotate by family, not just vegetable.

Garden practicesYou need to be aware of how your garden practices might be contributing to plant disease. First, you should water in the morning. When you water in the morning, the water can evaporate off the plant and soak into the soil before the heat of the day. Watering at night can leave the leaves of your plants wet, and wet leaves are more prone to disease. Also, be sure to water the roots, not the leaves. The roots need the water, the leaves don’t.

And clean your tools. If you have been trimming or pruning infected branches or leaves, wash your tools with a 10% bleach solution to prevent spreading the disease to other plants.

If these habits become part of your garden practices, you will be well on your way to minimizing plant disease and being a happier gardener.

Get answers to all your gardening questions by calling the Tulsa Master Gardeners Diagnostic Center at 918-746-3701 or email

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