San Augustine Lawn Grass Yellowing If you have yellow San Augustine in your yard, do not feel alone; if you look around, you will see many yards in the area that have yellow San Augustine this year.
What is causing the grass to be yellow? There are a few potential culprits in the case of the yellowing San Augustine leaves.
The first thing that comes to mind is a nutrient deficiency. Iron is commonly the cause of these pale-yellow leaves.
In high pH alkaline soils iron chlorosis is common. This chlorosis is more common during the spring when the plants are growing rapidly but can occur anytime during the growing season. Plants that have iron chlorosis will normally have green parallel stripes in a predominantly yellow leaf. If the problem is iron chlorosis the application of a foliar iron product like Iron Plus, or a soil application of iron sulfide should do the trick.
A nitrogen deficiency would be the next potential reason for yellowing grass. With a nitrogen deficiency, the whole leaf will be solid yellow with the absence of green streaking- the addition of nitrogen should fix the problem.
Many times, I find iron and nitrogen deficiencies together within a yard. If this is the case, using a combination of nitrogen and iron products should remedy the problem and turn your grass green.
The worst-case scenario and I have found several cases this year is Take-All Root Rot (TARR). I think the stress of the hard winter may have made our San Augustine more susceptible to TARR. If you have yellow spots in your yard and areas of dead grass, this is likely your culprit.
The areas of dead grass will continue to get larger. To determine if you have TARR, check the stolon’s of your San Augustine, if you find short brown or black roots then you know you have TARR.
If you have tried applying iron and nitrogen and you still have yellow grass, then you probably have TARR. The best treatment for TARR is to add sphagnum peat moss approximately 1” deep or 1 to 2 bales per 1000 square feet, over the infected areas. Soak the peat moss and irrigate as you normally would, the results can be excellent.