Despite recent droughts, one of the most commonly diagnosed plant diseases in Georgia is caused by excess soil water. This has been brought to a head by all the rain we have been seeing.
Dr. Alfredo Martinez, a UGA plant pathologist based in Griffin at the Georgia Experiment Station, told me that, “Out of all the samples of diseased plants that we get from homeowners, nurseries, landscapers and greenhouses every year, root rot is the problem more than 40 percent of the time.”
Martinez also told me that he noted root rot on a full spectrum of plants, including roses, marigolds, verbenas, hollies, box woods, azaleas and rhododendrons.
The problem with root rot is that the symptoms are often confusing.
People see plants that are wilted and yellowing, with stunted growth, and they naturally think the problem is lack of water — so they water more.
Unfortunately, the causes of root rot — pythium and rhizoctonia — are both very aggressive pathogens that thrive in wet soil.
If you have root rot disease, it’s primarily a water problem. Chances are, either the plant has been watered too much or the soil drainage is poor, or both. Most soils in the Bryan County area contain lots of sand and, of course, soils high in sand drain well.However, there is a great deal of clay I’ve found on the more northern end of the county. To find out how well your soil drains, try this test before you plant: Dig a hole a foot or so deep and about a foot wide. Then fill it with water. After the water has drained, fill the hole a second time. The water should drain out in 24 hours or less. If it takes more than 24 hours, you need to add topsoil, organic matter or some other amendment.
Also, bring your soil to the Extension Office to have a soil test done to determine what type and amounts of fertilizer are needed to boost plant growth. It’s much easier to improve the characteristics of the soil before planting than to treat diseases that might set in later.
One good watering each week is enough for most plants. Do, however, avoid light watering that gets the top layer of the soil wet but doesn’t penetrate the 3 to 4 inches plants really need.
Often people overwater simply out of habit or because the top layer of soil is dry. It’s important to check the soil from time to time to see how well it is draining and whether plants are getting enough or too muchmoisture. To do this, dig about 6 inches down to see how much moisture the soil contains. Don’t dig into the root systems of plants, but rather dig around them. But make sure you get down below the root zone — about 6 inches, in most cases.
If it’s dry and powdery that far down, it needs to be watered. Well-watered soil will stick together when it’s pressed into a ball.
Plant healthy plants
Another key to preventing root rot is to carefully check new plants before introducing them to the garden.
Contaminated soil is another way that pathogens or diseases can be introduced. Take one or two plants out of a flat of bedding plants and take a close look at the roots. Roots should be white or silvery. If they’re brownish, soft or sparse, then the plant is probably infected with a root rot-causing pathogen. Don’t introduce sick plants to the growing site.
If root rot is diagnosed, fungicides are on the market that, if chosen wisely, can reduce or alleviate the problem. However, the best thing to do is to correct the real problem: overly wet soil. After all, the root of the problem is in the roots.
If you have questions about plants diseases, contact the Bryan County Extension Service Office at 912-653-2231 or firstname.lastname@example.org.