Weekly Express-News Article
Saturday, August 6, 2005By Calvin Finch,
Conservation Director and Horticulturist, SAWS

“Brown Spots on the Lawn”

            Many lawns have brown dead looking areas.  There are many causes of the brown areas and in order to green the problem areas, you must diagnose the cause.  The brown areas usually are caused by drought, brown patch, take-all-patch, chinch bugs or grubs.  Drought is addressed with watering.  Brown patch is a fungus disease caused by excessive water and cured by reducing the watering and applying a fungicide.  Take-all-patch is a fungus disease that is controlled by acidification with spagnum peat moss over a long treatment period.  Both chinch bugs and grubs are killed by application of a soil insecticide. 

 

            The most common cause of brown areas right now is dead or dormant areas caused by lack of water.  It is very difficult to apply enough water to the lawn in the hottest part of the lot when we have a spell of 100º F days with no rain.  If your St. Augustine grass is brown at the edge of a shady area or next to the concrete driveway, suspect that the cause is drought.  The dead areas are usually linear rather than round and almost always are in full sun.  The areas can also be a spot in the lawn where the irrigation application of water is not even.  St. Augustine spreads fast so when the weather moderates or you can supply more water, the grass will fill in from the side.  One of the best strategies when you see these “hot spots” developing is to hand water the spots several times per week.  A little special watering to a small area is much more efficient than watering the whole lawn again. 

 

            Zoysia, Bermuda, and buffalo grass have the ability to go dormant when they do not receive enough water to stay green.  The pattern and location of dormant areas on these grasses can be the same as dead areas on St. Augustine, but usually the areas are less distinct.  There seems to be more blending between the brown dormant grass and the green part of the lawn.

 

            Brown patch is not too prevalent now because the weather is dry and hot.  It is a disease of the spring and autumn.  It usually shows a rounded brown area with an expanding edge.  Classic spots resemble a donut.  The hole in the center is formed by green blades that are re-emerging as the grass recovers at the center of the infection.  Brown patch fungus attacks the base of the blade but does not kill the roots. 

 

            Lawns at the bottom of the slope or lawns that are over watered are the most likely to have brown patch.  Brown patch fungus is why we recommend that homeowners water less and only water in the morning in the autumn.  Labeled fungicides will stop the brown patch fungus.

 

            Take-all-patch is another fungus disease.  It has an infection pattern similar to brown patch, but the symptom appears in the summer time.  Take-all-patch kills the entire grass plant and is very hard to control.  Fungicides do not seem to work.  Apply one-half inch of sphagnum peat moss over the dead area to encourage recovery of the area.  The spagnum peat acidifies which eventually kills the disease. 

 

            The brown spots caused by grubs appear in late summer or autumn.  They look like moth eaten areas with irregular ragged patterns.  Lawn areas killed by grubs come up in the hand like a toupee off a baldhead would.  The grubs eat the roots.  If the damage is caused by grubs it should be easy to find the pests in the soil under the toupees.  One problem in treating grubs is that it is too late when the damage appears.  The grubs quit feeding in late summer so the insecticides are not very effective.  They can be applied the next year in May or June to prevent damage again in the following year. 

 

            Chinch bugs cause damage that resembles the moth eaten damage caused by grubs, but the roots are still intact.  Like drought damage, expect chinch bugs to brown the lawn in the hottest part of the lawn, often along the concrete driveway or where the sun reflects off of the house.

 

            Chinch bugs are pinhead size bugs that suck the juices from the blade of the grass.  When damage is visible they are abundant enough to see when you brush your hand through the grass. Treat them with the same granular soil insecticides as you use for grubs.

 

            Diagnose the brown spots correctly and it is relatively easy to treat the problem.  If you do not make the right diagnoses, you can waste your time, and your money in applying the wrong treatment. 

 

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