For The Answer
Express-News Weekly Column
Saturday, September 5, 2003
Submitted by Calvin Finch, Ph.D., Conservation Director, San Antonio Water System, and Horticulturist
AUTUMN LAWN CARE
It is still mighty warm in San Antonio, but the days are getting shorter and we can expect a marked cooling of temperatures in September, especially at night. The change in the weather will mean that the lawn diseases and brown patch will become active again. Recognize the disease as a moving area of killed leaf blades. The leading edge of brown patch is often rounded as it moves equally in all directions.
Often, in the middle of the round killed area, some of the blades have been replaced so you have the look of a donut. The rounded, active disease edge moving equally from the infection center and the central donut hole showing regreening. Brown patch works at the base of the blades and does not kill the roots, that is why the lawn can repair in the donut hole while the outside of the infection is still spreading.
The brown patch infection can be stopped with a labeled fungicide such as Terrachlor (PCNB) or Fungaway (bayleton). Complete healing, however, will not usually occur until late spring.
The best way to control brown patch is to prevent an infection from the beginning. Brown patch does not develop in a dry lawn. One key to disease prevention is to reduce irrigation in September and October. Add a few days between watering and water no more than once per week. The time of the day you water also makes a difference. A lawn that is watered at night is more likely to develop brown patch than a lawn that is watered in the morning. The free water that sits on the grass blade all night is an ideal incubation environment for the disease.
Brown patch almost always begins in the lowest part of the lawn. Adding 1 inch of compost to these low spots raises them slightly, often enough to discourage development of the disease. Combine the top dressing with aeration and the lawn is even less likely to develop brown patch. The aeration and top dressing is best done in the winter, December through March. Apply one-half inch of compost over the whole lawn and 1 to 1.5 inches in the low spots from which the brown patch begins each year.
Take-All Patch, another fungus disease, may also be visible in your lawn now, is also treated with compost. Take-All Patch kills in a round pattern like brown patch but it kills roots and all. It is harder to treat than brown patch, no fungicides are very effective. Research at Texas A & M indicates that a compost product developed from cottonseed meal, HuMor, is the most effective treatment. The good news is that HuMor is only about $6 per bag. Apply it over the killed and adjacent area about one-half inch thick. The recovery of a lawn infected by Take-All Patch is much slower than repair of brown patch-infected areas.
Early September is also the time to treat your lawn with a pre-emergent herbicide, if you want to prevent winter weeds. Apply Amaze, XL, Balan, Betasan, or other herbicide granules to prevent clover, henbit, bedstraw, dandelions, annual bluegrass, rye, rescue grass, and other winter weeds from germinating. Read the label to pick the pre-emergent that best controls your worst pest. Some are more effective against grassy weeds and some prevent broadleaf weeds best.
If you wait until after the first cold wave moves through, some of the weeds will germinate before the herbicide can act on the seed in the soil.
You may also notice sometime this month that your lawn growth has slowed down. When day length shortens, hot weather grasses like Bermuda, buffalo, zoysia, and St. Augustine change from a growth mode to a hardened off state. The lawn grasses reorganize their nutrients and chemical reactions to survive the winter and prepare for next spring. Lawn fetilizer applied in late September and especially early October contributes to winter hardiness and a fast green-up next spring. On or about October 1 apply a “winterizer” lawn fertilizer. Common formulas include 15-5-10 and 18-6-12.