Yellow areas/ St. Augustine

13 years ago

I had posted awhile back that my lawn really bounced back and was looking good after a cornmeal application in mid Feb, followed up with Fertilome Southwest Green Maker a couple weeks later. The grass still looks real good overall except I have some areas that are yellowing. Still green but lighter than other areas. I notice it the worst in an area under and around a chinese tallow tree, but it is in other areas as well. This seems to happen every year but usually after a heavy rain. I recently watered giving it around an inch and it responded well with some quick growth, causing me needing to mow again after only 4 days where it had been around 7 or 8 days.

Years ago, I tried an application of Milorganite after the local nursery told me it would green it right up. Didnt really notice that much of a difference. The past few years I just kept up with my normal Soybean meal applications and didnt notice much difference in the yellowing after those applications.

So, cornmeal applied at 20 lbs per 1000 in mid February.

Fertilome product applied at recommended rate March 15th.

Any suggestions as to what might take care of the yellowing areas? It looks pretty healthy otherwise but I would like it all nice and green of course.

Could I apply another light application of the Fertilome in those areas, sort of spot treat? Especially around the Tallow tree (thinking it might be taking some of the nutrients from the grass) Or would I be wasting my time? Rain is expected in the next couple of days and it usually worsens a bit after a good rain.

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Comments (14)

botanicalbill
13 years ago
I would apply some dylox if you determin that you have pests such as cinch bugs.
Their symptom is a yellowing spot that keeps growing.
duajones
Original Author
13 years ago
I dont believe its chinch bugs or grubs but I guess I could be wrong
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It sounds like Take-all-Root-Rot from what you explained about the short black roots. Cut out a 1x2 foot section of the affected area and take it to your local extension office to have them examine it/determine what it is. This disease is primarily observed during the summer and early fall months. By the time the leaf symptoms appear, the pathogen has been active on the roots for at least 2-3 weeks, probably longer. Any stress placed on the grass will encourage or worsen the disease. This disease is very difficult to control once the above ground symptoms are observed. Therefore, measures that prevent or alleviate stress are the best methods for completely controlling the disease or at least decreasing the potential damage. Because the roots are affected, they will not be able to efficiently obtain water or nutrients from the soil, nor will they be able to store the products from photosynthesis. Here are a few things to do NOW. 1. Frequent foliar (leaf) feeding of all nutrients (N, P, K and micronutrients) in small amounts will be necessary. The roots are not functioning properly, and so will not be able to efficiently obtain nutrients from the soil. Spray Soluable Seaweed powder weekly with a pump sprayer/fine mist until the leafs are wet. Spray in the early morning or late evening. Use molasses as a wetting agent. 2. Extra potassium is useful in late summer and early fall. Use Sulfate of Potash if staying organic. Apply immediately @ 2-lbs. per 1000sqft. Do not apply lime or herbicides. Raise the mowing height to the highest recommended height/slightly higher until conditions improve. Mow as frequently as necessary so that only one third (1/3) of the leaf tissue is removed.
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It's not SAD, it's normal. It has happened to me for 15 of the last 20 years with no apparent permanent issues. Besides 1 inch of mulch over top of St Aug is GUARANTEED to suffocate it and eliminate the lawn completely. But I'm not surprised TAMU would come up with that bonehead diagnosis and worse solution. That is a great picture. I've been trying to find a good lawn to use for an example of this problem. The problem is the heavy rains we had washed all the acidity out of the soil. When that happens, the pH at the very surface goes to 8.0 and the iron becomes bound up and unavailable to the plants. If you do nothing, it will remain that color for the rest of the season, and next spring, all will be great again. You may not remember that you had a problem. What seems to happen over the winter is the soil pH in the upper root zone becomes more acidic...just enough to release the iron for uptake in the plants. At this point, no matter how much iron product you apply, the high pH will never allow it to reach the plants. One product that seems to work, and the reason is not crystal clear, is called greensand. The actual material is glauconite (GLAW co nite). It is mined from ancient seabeds in various places around the country. It is sandy and has a greenish tint. Apply at 40 pounds per 1,000 square feet and you have a chance of full recover this season. If you live north of Austin, I would not bother for this year. If you live south of a line from Corpus to Laredo, then you might want to go ahead and do it, because you have many weeks of active growing grass left this season. I live in San Antonio and have a house in George West - I'm not going to use it on my lawns. At least you can live in comfort of knowing the problem happens all the time. It has no effect on the health of the grass or soil. The reason it happened to you and not your neighbors might have to do with the fertilizer they use. If they use one with ammonium sulfate, it could be their pH is lower. I use only organic fertilizers with no "acidifiers," so if it is going to happen, it seems to happen to me. Greensand clears it up after about 3 weeks. You should be able to get greensand at any good nursery or garden center. This only happens in years with heavy rains. One year we had a low pressure system stagnate over top of us dumping 20 inches of rain in a week. At about day 4 of that event, I realized what was going to happen and applied the greensand while it was raining. It worked perfect! I had the only deep green lawn for the rest of the year while everyone around me went entirely yellow.
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Alph
13 years ago
Is it in the shade most of the time?
duajones
Original Author
13 years ago
the area under the tallow tree, yes
why do you ask?
ltruett
13 years ago
Have you tried something containing iron? If you are going to organic route, you can use greensand. Otherwise you can try ironite or something like that. I would also do another application of fertilizer such as soybean meal or cottonseed meal.
Alph
13 years ago
If you cut back on the water in this area, I believe it should return to normal. It is at least worth a try.
duajones
Original Author
13 years ago
The lawn hasnt been overwatered at all. Hardly any rain in the past 2 months and I have only watered twice.
I did get around an inch of rain this morning and that usually worsens the problem.

I have thought about trying ironite but as I mentioned before I didnt have any noticable results back when I used milorganite so wondered if the ironite would be a waste of time. Greensand didnt give me any noticable results either. I had forgot that I tried that a few years ago as well
ltruett
13 years ago
Any idea of the type of St Augustine you have? You might try a different variety such as Floratam or Sapphire and see if that helps.
nandina
13 years ago
I had the same problem in my front lawn. Was pretty certain that it was chinch bug but could not find any. Kept checking and finally found them at high noon under hot sun which is their most active period. Treated with an insecticide to which I added a sticker, spread Ironite and lightly tossed Epsom salts on the affected areas. Saw signs of recovery in a week and complete recovery in another week. Suggest you assume the problem is chinch bug and treat those affected areas with one of the recommended insecticides following label instructions.
duajones
Original Author
13 years ago
While mowing yesterday afternoon I noticed birds coming in to feed on what looked like small moths. It looks like they may be the adult stage of sod webworms that are picture in the link below. I may have chinch bugs as well.
I will use an appropriate insecticide here in the next few days and would like to try some ironite but the temps are a bit too high for that I believe

Here is a link that might be useful: link
Alph
13 years ago
I believe it is due to the lack of sunshine. Which could explain why it gets more yellow during a rainy day as there is less light source.
duajones
Original Author
13 years ago
Sprayed with triazicide a few days ago and the sod worm moths were very visible. Mowed yesterday and no sign of them, the birds were dissapointed. I do plan on following up with a light application of iron to help with green up.
Overall, the lawn looks real good with the exception of a little discoloration.
duajones
Original Author
13 years ago
Thought I would bring this thread back up and add some pictures. These were taken in 2006 and you can clearly see what I am describing. The yellowing areas arent this bad right now but probably will be. So it has been persistent.
I am thinking about spreading some hi yield iron plus which has iron and 11 percent nitrogen I believe.
Anyone have a better idea?

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User
13 years ago
I suspect iron deficiency caused by too little oxygen in the soil.
Since the roots can't uptake any iron might spray a foliar iron
supplement. Do it in the cooler part of the evening and if it's
over 92F rinse the foliage the following morning to prevent
possible leaf scorch. A few drops of liquid soap (Murphy's) will
allow the spray to cling to the grass better.

Yellow areas/ St. Augustine

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