Healthy lawn prevents patch

Those of you who read my columns on a regular basis know that take-all patch is the most destructive disease we have in our lawns, particularly on St. Augustine. If your lawn has a history of this problem, now is the time to be treating with a fungicide.

Take-all patch, like most on our warm-season grass diseases, is most active in the spring and the fall, specifically in the spring during greenup. Initial symptoms of take-all patch are circular to irregular straw-colored to light brown thinning patches anywhere from 6 inches to 3 feet in diameter in the turf. As the disease progresses, patches can come together, eventually killing large areas of the lawn. The patches can reappear in subsequent years causing extensive damage to turf.

Take-all patch is sometimes confused with brown/large patch because of similar symptoms. These two diseases can be distinguished from each other by pulling on a yellow or brown blade of grass. The blade infected with large patch will give some resistance when pulled on, whereas the turf infected with take-all patch will easily pull from the ground. Also, the stolon infected with brown patch will not be brown/black as with take-all patch. Even with these descriptions, it can be hard to tell in the field.

Take-all patch causes affected stolons to be easily pulled from the ground because of the root rot infection that takes place. The roots will be blackened, shortened, and rotted.

Integrated management is the best approach to preventing and controlling take-all patch in lawns. Take-all patch problems are closely related to soil pH. Maintaining a pH below 6.5 will reduce the severity of the disease. This is why I recommend never liming your lawn unless you take a soil test first. If your soil pH is above 6.5, acidifying fertilizers such as ammonium sulfate can be used to lower it. Conversely, you don’t want the pH to be too low (i.e. 4.5 – 5.3) as this will tie up most of your nutrients where they are not available to the grass.

I urge everyone who has a disease problem in the lawn to make sure they take a soil sample to find out, not only the pH, but all other nutrient levels. One of the keys will be the potassium level. I can almost guarantee that when a grass has a disease problem like take-all, the potassium levels will be low.

Potassium is a very important element in growing grass. It is specifically known to help in the prevention of disease and helps with winter hardiness.

Potassium is the second most-used element in grass (nitrogen is first) and is second most that leaches out of the soil. In the absence of a soil test, the best fertilizer is one with a 2:1 nitrogen to potassium ratio (such as 16-4-8).

Manganese deficiency also increases the severity of take-all, so supplements of this can be added. A good fertilizer with micronutrients will contain manganese.

Like most diseases, take-all patch is associated with stressed lawns. Management for this disease involves good cultural practices such as:

• Provide good surface and subsurface drainage. Core aerating a lawn in the spring can help with this.

• Water the grass infrequently but deeply. Water the grass when it needs it and not on a regular schedule.

• Mow at the proper height for your particular grass.

Fungicides can help control this disease, but they have limited effectiveness during the summer when a lot of the symptoms show up. Research has shown that the only effective times to treat are in the fall and again during early spring. After your initial application this spring, follow it with a second treatment about three to four weeks later.

When selecting a fungicide, look for Immunox Lawn Disease Control (liquid) or Fertilome F-Stop (granular) that contain myclobutanil. These two products are what you will find in most retail garden centers. There are numerous other fungicides labeled for take-all, but you will have to go to one of our local stores that cater to the commercial landscape industry.

Topdressing with peat moss seems to help control take-all patch disease. The recommendation is 3.8 cubic feet of sphagnum peat moss per 1,000 square feet.

There are other things to think about when trying to limit this disease. Don’t fertilize the lawn earlier than April 15th. Fertilizing in March can make take-all worse. It will be beneficial if you aerate the lawn after complete green-up (after May 1). You might also try top dressing with compost, which has anti-fungal properties.

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