Rainy, cloudy weather not good for Southern staple — greens

Published 12:00 am Sunday, October 18, 2009

We southerners love our greens. In fact, dark, leafy greens are some of the most nutrient-dense foods around. Greens are like the superheroes of the vegetable world. Unfortunately, those superheroes have had to battle with very unfavorable growing conditions thus far this fall.

Greens— the leaves of turnip, mustards, collards and other related species — are the mainstay of the southern fall garden. Ordinarily, these plants are very easy to grow but the rainy, cloudy weather we have been experiencing over the last several weeks has caused several bacterial and fungal leaf spot diseases. Greens with these leaf diseases certainly have much less appeal to the greens aficionado. 

John C. Coccaro is county Extension director. Write to him at 1100-C Grove St., Vicksburg, MS 39180 or call 601-636-5442. E-mail him at jcoccaro@ext.msstate.edu.

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Some of the common diseases we are seeing now include anthracnose, cercospora leaf spot, white spot, downy mildew, and bacterial leaf spot. These diseases can be spread by wind or rain and are strongly favored in wet conditions like we have had. Anthracnose can come from a variety of hosts, but weeds surrounding the garden probably account for most of that disease. The pathogens that cause cercospora leaf spot and white spot can also come from various sources, too, such as volunteer plants, perennial weeds and occasionally from infected seed. Downy mildew and bacterial leaf spot thrive when daytime temperatures stay below 75 degrees.

If our daytime temperatures drop just a few degrees, we should soon be out of the ideal range for anthracnose, but favorable temperatures for the other diseases will be with us into next month. Each of the diseases has their own unique appearances on the leaf with variations in the color or shape of the spots. Severe cercospora infections can sometimes defoliate the entire plant. Downy mildew can spread extremely fast under wet, cool conditions, and bacterial leaf spot often results in greens with a ragged appearance. 

Unfortunately, there is very little that the gardener can do about these diseases after-the-fact. Fungicide applications have little to no effectiveness on most of these diseases. In addition, most garden fungicides have withdrawal intervals that last beyond the number of days the greens would remain tender. 

If your fall garden’s greens are currently being affected by one or more of these foliar diseases, what should you do to ensure better success next time? 

Soil test and fertilize according to test results to ensure adequate, balanced fertility.

Plant certified seed or healthy transplants. If certified seed is not available, use an approved seed treatment.

Practice good weed control in and around the garden.

Practice crop rotation and do not grow greens on the same spot for three years.

Remove any diseased plants immediately.

Till all old crop debris immediately after harvest to allow time to rot.

Work in the garden only when plants are dry to prevent spreading disease with your hands, tools or clothing.

Of course, those are management practices the gardener can control. Weather conditions, however, are in the hands of Mother Nature, so we’ll just have to hope she chooses to cooperate.