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Basil Downy Mildew can spread like wildfire throughout a large planting, completely destroying it in just a short period of time.

CONTRIBUTED PHOTO FROM LEE ROUSE, LSU AgCENTER

Sweet basil is one of the easiest herbs to grow in the garden. It can be an annual or a very short-lived perennial.

Many gardeners like it for its strong, fresh clovelike scent, as well its small white flowers that bloom in late summer. And of course, there's the culinary benefits. What you might not know is that this plant is also pollinator-friendly, attracting honey bees to the garden.

Basil can be grown very easily from seeds, cuttings or transplants. It needs very little fertilizer and, once established, has minimum water requirements.

Though basil is very easy to grow, there is one significant disease, basil downy mildew, which can completely destroy and ultimately kill your plant.

Under some weather conditions, basil downy mildew can spread like wildfire throughout a large planting, completely destroying it in just a short period of time. The disease can be identified by the yellowing of leaves, which restricts major veins, resulting in the entire leaf turning yellow. You may also see irregular black spots on the leaves in the infected area as the disease progresses. Over time, fuzzy gray spores will grow on the underside of an infected leaf.

This disease usually starts at the bottom of the plant and works its way up.

Unfortunately, there are no varieties of sweet basil that are resistant to basil downy mildew, and chemicals won't prevent the spread of the disease.

Infected basil should be dug up and disposed of by double-bagging the plant and putting in the trash. Be sure not to compost any infected plants. It is never a good idea to compost a diseased plant, as you run the risk of spreading the disease to healthy plants.

There are a few cultural control options to prevent downy mildew from occurring on your basil. The first is to make sure plants are spaced properly. Placing plants too close to each other limits air flow, which means leaves remain wet longer and that can result in the spread of diseases.

Though basil downy mildew will kill basil, do not let this disease steer you away from planting it in your garden. Through proper cultural control options, you can prevent this disease. And there are too many benefits that outweigh the risk.


Got a question?

Email gardennews@agcenter.lsu.edu.