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GRAY LEAF SPOT -
Ugly? Yes!!
Impossible to Control? No!!!
(Despite What Some Lawn Service Might Tell You)
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This is the time of the year -- thanks in large part to the weather and our fertilization schedule -- that the disease Gray Leaf Spot rears its ugly head. Before I get to the basics of the disease and its control, I want to give you a warning. While I may be preaching to the choir, I still think it's worth mentioning.
And that story involves some unscrupulous lawn maintenance companies. Simply put, they are trying to scare the unknowing public into their service, by claiming some very untrue things.
 Example #1: If anyone tells you that this disease is so "terrible" that if you don't do something about it "very soon" you could lose your whole lawn even sooner… Well, that's a load of %#@*&%$. Granted, if left untreated for years, it could look pathetic, but rarely ever is it life threatening.
Example #2: Then, said lawn maintenance companies have the nerve to tell you that they have the only "approved" fungicide capable of solving the problem… Which is laughable considering Daconil (Chlorothalonil) is the most often approved choice of fungicides for Gray Leaf Spot. And Daconil can be found at any place that supposedly sells gardens supplies.
So, what I've really done is gone a long way to prove a point - and that's that you can take care of this problem yourself. So, here are some of the technical descriptions pulled from various university research papers regarding GRAY LEAF SPOT.
Gray Leaf Spot (Pyricularia grisea) may be showing up because of nighttime watering, frequent rainfall, high humidity, heavy dew (i.e. prolonged leaf wetness), plus rapid, lush growth courtesy of recent fertilizations.
Lawns with severe gray leaf spot have areas that seem to just fade or melt away. The decline often starts in shaded locations and low spots with poor drainage. Individual leaf spots on grass blades are typically elongated with dark margins.
Management practices are very important for gray leaf spot control.
1. Do not over-fertilize;
2. Do not water at night;
3. Mow frequently;
4. Catch clippings in problem areas. As grass growth slows in late July and August, and rain frequency decreases, gray leaf spot usually subsides. Fungicides can be used to control gray leaf spot, but control may be difficult if the disease has already done significant damage.
The "spots" associated with Gray Leaf Spot, first appear as tiny brown to ash- colored spots with purple to brown margins that enlarge and become diamond-shaped. Lesions begin as tiny, round or oval gray to brown or black spots on leaves. Spots enlarge into oval to elongate areas on leaves, sheaths, and stems, with the size dependent on the species and variety. Spots may be surrounded by a yellow halo or general chlorosis with purple to brown borders. Leaves may be blighted gray, usually from the tip downward. During moist periods, lesions become covered with a gray, velvety fungal mycelium. Diseased blades may wither and turn brown giving them a scorched appearance.
Besides the more commonly found Daconil Fungicides, these fungicides (which are much harder to find and often times more expensive) are also approved for use on Gray Leaf Spot.
Banner, Banner-Maxx, Duosan, Heritage.
Until next issue, here's to
Great Gardening from the GardenLine, heard
exclusively weekend mornings from 8 to noon
on Talkradio 950 KPRC.
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