July 2010 Newsletter©
Lawn Diseases
A mild winter, followed by a wet spring and a hot, humid summer (the very definition of Memphis) makes turf grass prone to disease. Turf diseases can be one of the most frustrating gardening experiences you have and probably the most expensive cure.
Proper maintenance will help you avoid some problems. Water in the morning, de-thatch when needed, bag your clippings (especially diseased tissue), avoid over-watering and especially over-fertilizing and rake up your leaves before winter sets in. Areas that are known to be wet through the winter or are currently infected should be treated with a fungicide in the fall because the fungal spores winter in the thatch layer and it is easier to prevent than cure. Aeration of infected areas prior to a fungicide treatment in the fall is advised. Alternating fungicides is advised on heavily infected areas or on difficult to control diseases. Treat areas prone to fungal problems with 2 lbs. of potassium per 1000 sq. ft. in the fall.
Here are the most common Mid South problems and the products you should use for control: Heritage is a little pricey but it’s the only control for some problems. It is a special order item. We stock the other five products.
1. Ferti-lome Systemic Fungicide – Propiconazole – aka Banner Maxx
2. Ferti-lome F-Stop – Myclobutanil - aka Eagle
3. Hi-Yield Turf and Ornamental Fungicide – Terraclor – aka PCNB - Pentachloronitrobenzene
4. Heritage – Azoxystrobin
5. Monterey Agri-fos
6. Ferti-lome Halt – aka Cleary’s 3336
Brown patch (Rhizoctonia solani) Use 1, 2, 3, 4 or 6.
This is the most common lawn disease. It occurs most often in the spring but can appear in the fall. Conditions are suitable for brown patch when you have warm days (70° - 85°), cool nights (below 65°) and moist foliage. The grass appears to have circles of yellow to brown foliage, usually surrounded by a dark outer ring. Water early in the day and bag when mowing.
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Dollar Spot (Sclerotinia homeocarpa) Use 1, 2, 3, or 6.
In severe cases, dollar spots may be so numerous that the disease is often mistaken for brown patch. Normally the disease appears as small circular, straw colored patches. Avoid excessive nitrogen and dry soil; both tend to encourage dollar spot.
Fairy Ring Use 4.
Isn’t this one cool? It’s not if you’re trying to cure it. There are over 50 different fungal species that cause fairy ring. The fungus starts in decomposing organic matter, usually an old tree stump, and then progresses outward. At the leading edge, the grass is often dark green and lush from the nitrogen being released as the fungus does its thing. Inside the ring, a thick layer of white, root-like mycelium forms beneath the surface that is often so thick that water and grass roots will not penetrate causing the grass to brown. The mushrooms appear occasionally along the outer rim of the circle which may be as large as 50’.How much the grass suffers appears to depend on the type of grass and the variety of fungus involved. Some fungi cause the grass to die from hydrogen cyanide production. It gets its name from folklore. When the mushrooms appeared, it was believed fairies danced there during the night. Aeration as well as a fungicide treatment will be necessary to control it.
Gray Leaf Spot (Pyricularia grisea) Use 1 or 4.
This is a disease of fescue, perennial ryegrass, St. Augustine and occasionally centipede. This disease spreads very rapidly and can kill large areas of turf. It resembles other diseases but many chemicals that control other diseases do not suppress this one so quick, positive identification is important. It begins with small purple lesions that enlarge giving the grass a burned appearance. Store a sample in a plastic bag overnight and the foliage will be covered with grey mold in the morning.
Greasy Spot (Pythium aka Cottony Blight) Use 4 or 5.
Most often occurs is areas of poor drainage and air circulation. It causes patches of matted, slimy grass and often appears to follow mowing patterns as it can be spread by equipment. Leaf blades are often covered with mycelium that gives it a cottony appearance.
Leaf Spot (Dreschslera poae) Use 1, 2, 3, 4 or 6.
This is primarily a disease of fescue, perennial rye and bluegrass. Purple lesions form on the blade and from a distance the grass will have an off-color appearance. Leaf spot occurs in hot weather during spells of heavy dew. Temperatures over 85° may lead to crown rot in infected turf causing large patches to die. Avoid mowing below 2” in height, fertilize lightly in the spring, heavier in the fall.
Melting Out (Bipolaris sorokiniana) Use 1, 2, 3, 4 or 6.
This disease resembles the leaf spot above and was once thought to be the same disease. Melting out however occurs in cool, rainy weather often when excessive nitrogen fertilizer has been applied. Like above, avoid low mowing and apply most of your fertilizer in the fall.
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Rust Use 1, 2 or 4
Rust gives the turf a yellowish cast. If you examine the leaf blades, you’ll find orange pustules. These pustules are easily ruptured and the disease can be spread by equipment or on your orange stained shoes. The disease most often attacks slow growing turf when temperatures reach 55° or so and there are long periods of dew. More often attacks cool season grasses but fairly common on bermudagrass. Increasing nitrogen and mowing frequency aids in recovery.
Spring Dead Spot Use 1, 2 or 4.
This disease causes crown, stolon and root rot in dormant hybrid bermudagrass. It’s caused by three separate fungi working together. The affected areas are normally circular in shape, from a few inches to a few feet wide, and the grass appears straw colored. Little if any re-growth occurs in the summer and the disease returns and enlarges the following year. Avoid over fertilization and apply potassium as mentioned above.
Zoysia Large Patch (Rhizoctonia solani) Use 1, 2, 4 or 6.
This disease of Zoysia starts as small circles, usually a foot of so in size, and rapidly expands. It causes the turf to thin and appear off-color. The circles are evident in both growing and dormant Zoysia. It is most often seen in temperatures of 50° - 70° with long periods of dew. Easily spread by grass clippings, so bagging is mandatory. Caused by the same fungus that causes brown patch in bermudagrass, it seldom kills zoysiagrass but causes thin, unattractive turf.
This was June’s contest. Two plants…get either one correct.
Left picture is a Ligularia ‘The Rocket’. It’s a great, large growing, shade perennial for a damp to wet location.
Right picture is a Bletilla or hardy orchid. This is a great plant for the edge of the shade garden where it can get a little sun.
Here’s this month’s contest. What is this pretty little orange flowered plant?
The contest ends on July 15th. Drop by either store to enter or you can email your entry to
questions@danwestonline.com. One winner, selected from all correct entries, will receive a
$25 Dan West Gift Certificate.
Thanks for shopping with us at Dan West.