Plant Answers

Dead Spot in the Lawn—Why?

“Help! I have an ugly dead spot in my lawn and I don’t know what caused it.”

If I have heard that comment once, I have heard it a million times. The conversation then drifts into a hypothetical discussion and description of
what may or may not have caused the dead spot. The most common “lawn killers” are improper mowing, irrigating lightly and frequently, compacted soil and insects or disease damage.

A. Mowing Height. A lackadaisical notion that lawn mowing is no big deal gets the homeowner in trouble every time. The single most important cultural practice to maintaining a beautiful lawn is mowing. Poor mowing practices can have many devastating effects on the lawn that no amount of fertilizer or water or pesticides can correct. The three most common mowing errors are improper cutting height, improper mowing frequency and mowing with a dull blade.

Turf grass researchers have identified the ideal cutting height range for each of the turf grasses we use for our lawns:

Hybrid or “Tif” Bermuda grasses ½ to ¾ inch
Common Bermuda grass ½ to 1 inch
Zoysia 1 to 2 inches
St. Augustine 2-1/2 to 3 inches, or as high as
your mower will cut

All should be mowed every 5 to 7 days as less frequent mowing at
these recommended heights results in scalping and generally poor quality
turf. Make sure you know which turf grass is in your lawn and set your
mower accordingly.

If your lawn is a mixture of two turf grasses such as common
Bermuda and St. Augustine, use the proper height for the grass you want
Encourage. If you want St. Augustine, cut at 3 inches. The Bermuda grass
will hate it. If your lawn is shaded or receives heavy use, move the cutting
height up one-half inch or so from the above ranges. Also, mowing at the
highest level of the range helps conserve water by acting as a living mulch,
shading the ground and preventing evaporation.

Of equal importance to cutting height is mowing frequency. Associated with mowing frequency is the somewhat controversial subject to of whether the clippings should be removed from the lawn. How often you mow your lawn depends on its growth rate. Mow when the turf height is no more than 1/3 of the leaf blade is removed at any mowing. If the mower is set for a 3-inch blade cut, the lawn should be mowed when it reaches 4-1/2 inches in height. If this criteria for mowing frequency is followed, clippings will not need to be removed. They will simply fall back into the turf and the nutrients they contain (up to 3 percent nitrogen) will be available for future use by the lawn as decomposition occurs.

Since the criteria for mowing frequency is dependent on the growth rate of the lawn, and since fertilizer plays an important roll in determining the lawn’s growth rate, you must use common sense when fertilizing your lawn. If you have to mow the lawn too often (St. Augustine should not have to be mowed twice a week!), you should consider reducing the fertilizer application rate, or use a fertilizer that has at least 50 percent of its nitrogen in a slow release form (i.e., sulfur coated urea). To grow properly, St. Augustine lawns need only two applications of fertilizer—an application of a slow-release form in the late spring and a “winterizer” type (4-1-2 or 3-1-2 ratio) in October.

Probably the most common violation of the lawn care rules is mowing with a dull blade. Blunt blades rip and tear the turf leaving a hazy, grayish appearance to the shredded lawn. A sharp blade will glide through the turn grass making mowing easier. Make it a habit to have your blade sharpened every winter while the mower is not in use. It is wise to have the blade sharpened by a professional and make sure that he balances the blade after sharpening.

One of the benefits of proper mowing is weed control. Few weeds can compete with the rapid growth rate and dense turf of a properly mowed lawn.

And last, but certainly not least, is when to mow. DO NOT, hear me, DO NOT MOW GRASS WHEN IT IS WET! Not only will it stain your clothing and clog the mower, but as you trot merrily around the damp lawn you become a disease spreader. Worse than Typhoid Mary, your wet body parts and the lawn mower act as a vehicle of transport for one of the worse fungus diseases of turf grass in Texas—Brown patch.

B. Irrigation. If you irrigate more frequently than necessary, and you water lightly, the turf grass plant does not develop its full potential for rooting depth. By observing indicator spots that first exhibit wilting—as evidenced by a bluish-green color, foot printing, or the rolling, folding or drooping leaves—you can obtain some guidance as to when to irrigate. Don’t water more than you need to, but certainly enough to keep your lawn green and healthy. Dead spots are unsightly and difficult to repair.

C. Traffic. Recreational turf is subjected to wear on the above- ground plant parts and to soil compaction. Wear of the turf grass shoots causes the grower to force a faster growth-rate with more nitrogen and water. Also, recreational turfs are often mowed closer because of their use. Soil compaction reduces rooting and thins out the turf so that more frequent irrigation is often applied. Also, reduced infiltration under compaction encourages the person doing the watering to go to a more frequent, light application schedule.

Pets, especially big dogs, can cause dead areas. For more details, see:

http://aggie-horticulture.tamu.edu/plantanswers/turf/doglawn problems.html.

D. Insect or Disease Damage. One problem could be white grubworms in the soil. Generally, if this is theproblem, the area of lawn should have died late alst fall. The entire area of the lawn should be dead, no green sprigs, and the dead grass can be easily lifted incarpet-like sections. This lack of root anchorage is due to the eating off of roots by grubs. What should you do? Actually, the question is—what should you have done last July! The white grub worm (white worm with hard orange head) is the immature stage of the June bug which flies around lights and into your hair in May and June. These June bugs depositegss in lawns in early July. An application of granular insecticide approved for grub control at that time will kill the young grubs and save lawns. See:

http://bexar-tx.tamu.edu/HomeHort/F1Column/2004Articles/JUNE27.htm.
Another problem that weakens areas of lawn grass every fall, and possibly thins the turf significantly is brown patch. Brown patch is a fungal disease that begins in a small area and spreads in a circular pattern. The pattern resembles a balloon being filled with air—it gets larger and larger. Brown patch will only occur on grass that has previously greened in the spring so it cannot be confused with grubs or cold injury. It can also be distinguished from other lawn problems by the presence of dark, smoky rings on the edge of this ever-enlarging ring. There will also be green sprigs of grass within the affected circle.

But suppose you have Brown patch-like symptoms in the heat of summer? Unlike Brown patch that is normally a circular area with the edge of the circle having browning or yellowing grass and the interior of the circle having a more healthy green appearance, this patch disease symptom has brown, dead grass throughout the circle. This summer-patch disease is referred to as Take-All patch. For control measures of Brown patch and Take-All patch, see:

http://www.plantanswers.com/brownpatchfungus.htm

As if these weren’t enough possible problems, there is another villain called St. Augustine Decline or “SAD”. It is what it says it is—a gradual declining or thinning of St. Augustine grass. It is caused by a virus and displays the symptoms of mottling or spots of yellow on green grass blades. The affected grass blades look as if they have been splattered with yellow paint. Notice I said spots, not streaks. See the image of St. Augustine Decline on grass blades at:

http://www.plantanswers.com/questiongrassthinning.htm

and

http://www.plantanswers.com/staugustinedecline.htm

Streaks of yellow and green indicated iron chlorosis which can be corrected
with iron sulfate (copperas) or an iron chelate material. For images, see:

http://www.plantanswers.com/staugustinedeficiency.htm

St. Augustine Decline occurs mainly on older, established lawns. The lawn
gets thinner and thinner until finally it is a mess. The only, and I stress
ONLY, remedy is the Decline-resistant Floratam St. Augustine grass. See:

http://plantanswers.com/grass.htm

These are some of the possibilities of what caused the dead spot of
grass in your lawn. I hope that you can identify one or some of the culprit
grass killers so that you can prevent a similar occurrence.

Bermuda Grass Replacement for St. Augustine
The “Smart Choice” for a Full Sun Lawn

What kind of grass should I plant? Which one of the new “miracle” grasses
is really best for renovating my lawn which was damaged by winter freezes
and summer droughts? Should I sprig or lay sod? These are questions
which seem to be eternal in this area. My question is, “why even replant
anything?” I have the ultimate, practical solution for ensuring that you can
grow a lush lawn grass. The wonderful part of this plan is that it is cheap
and not labor intensive. Not only is it cheap and easy, but this plan will
result in the enhancement and establishment of one of the most drought
tolerant turf grasses available.

The grass that will effortlessly enhance your landscape is the type of grass
most widely used for golf courses in the world. Care and mowing of this
adapted grass can be determined by each individual homeowner. If an
individual wants a quality, highly manicured turf with a sophisticated look,
this grass can be mowed every five days, fertilized monthly and watered
thoroughly weekly to produce the most luxuriant grass in the world.

If on the other hand, you want to neglect and abuse this grass during hard
times of water rationing and provide minimum feeding*, this turf will
survive in a dormant state and wait until the “good times of natural lawn
stimulation (water and fertilizer) occur again.

*Fertilize this turf with a slow-release type in April and July, and with
a “winterizer” in October.

Does this sound too good to be true? Well, it can be a reality in your lawn
within six weeks IF your grass is growing in a sunny exposure.

For those of you who are attempting the impossible task of growing and
maintaining turf in the shade of trees, I recommend the swept-sod technique.
The swept-sod technique involves killing all of the barely surviving grass,
weeds, sprouts, etc. that grow in shady areas with a herbicide containing
Glyphosate. Then you have the choice of swept-sod/rock or going to the
expense of establishing a shade-tolerant groundcover such as Asiatic
Jasmine or English Ivy.

The sweep sod/rock technique involves less inputs but may provide a less-
than-desirable neighborhood appearance. It seems that some nosey
neighbors protest when folks in the area begin to stir up clouds of dust as
they maintain the turf-no-more area by sweeping the bare ground with a
broom. For concerned, amicable yet conservation-minded, shade-burdened
folks who don’t want to irritate neighbors with the dust-stirring sweeping
activity, I recommend the use of large, flat rocks which can be easily
maintained during periods of rain or drought. Large, flat rocks are also
excellent mulching material and are extremely wear tolerant in case you
have an athletic group who want to play under the trees. Weed and grass
control on rocks is minimal!

Those of you with a sunny landscape can easily establish and maintain the
absolute best turf grass for this area. In fact, most people already have it
growing in their lawns but have not enhanced its growing conditions so that
it becomes the predominant type. The surviving grass is what has been
tried-and-proven by the existing environment in your lawn to be the best so
why try to grow something else?

The grass that is surviving in sunny lawns in this area, is the most widely
planted on golf courses, is the most drought-, heat-, and abuse-tolerant is
Bermuda Grass. It tolerates, actually appreciates, low mowing heights that
damages most St. Augustine grass. Most lawns in which Bermuda grass is
sprouting out of the St. Augustine can be effortlessly purified to a pure stand
of Bermuda grass and weeded by spraying with a commonly available
herbicide sold as MSMA or DSMA.

Bermuda grass is the ONLY adapted grass species for this area which
can be established by planting seed. To successfully get Bermuda seed to
germinate and prosper, there are several things you need to do. First, the
ground temperature must be sufficiently warm for the seed to germinate
(approximately 80 degrees F.) so do not even try it until late May, and stop
seeding by late September. The seed should be strewn on the surface of the
soil and gently raked in (like with the back side of a leaf rake). The soil
surface must then be kept moist for about three weeks to insure that the seed
have enough moisture to germinate and then get its roots established into the
soil. This usually requires watering once or more times each day.

For more about Bermuda, see:

http://aggie-horticulture.tamu.edu/PLANTanswers/turf/publications/bermuda.html

If you are concerned about Bermuda “jumping” into your flower beds and garden area, there are now some products which will kill ONLY true grasses such as Bermuda, and not damage your other ornamentals. They are sold as Grass-B-Gon, Over-The-Top, Fusilade, Poast, Vantage, Ornamec, etc. Read and follow label instructions and you can easily control the grass of choice for all of Texas—Bermuda grass.