June 28, 2011

Here's Randy's Weekly KTRH GardenLine Tip:

Issue #264

Some painters transform the sun into a yellow spot, others transform a yellow spot into the sun. ~ Pablo Picaso

While Picaso had a great take on the color yellow, few of us appreciate yellow in our turfgrass. And since I've been getting a lot of calls and emails lately about yellowing St. Augustine, I guess it's time to look again at all the possibile causes and methods for dealing with each situation.

Lately, the questions are mostly related to a chartreuse color ... or a faded green. Sound familiar? With all the watering we are doing, thanks to rainfall deficits and 100-degree temperatures, I'm not surprised.

First, let me get the most obvious out of the way: If you have not done the summer fertilization, because you thought it was too hot, there's your answer. Remember what we say — "It's never too late to do the right thing." So you can and should apply fertilizer per my schedule.

While excessive watering could be to blame here, a number of other things could also cause this malady. In my lawn fertilization schedule, we sort of take into account the possibility of yellowing in July and August. Most often it's a deficiency of nutrients ... either Iron Chlorosis or Nutrient Lock-Up. You may notice the discoloration is under tree canopies, especially pine trees and crape myrtles.

So, here's what I reccommend for chartreuse to pale-green grass. First, approach it as if it's Iron Chlorosis — a need for iron and soil acidifier. Put down any iron/acid combo you can find, and water it in.

Products you've heard me recommend for iron treatments:

• Dr. Iron from Monterey
• Iron Safe (if still available) by Lillie Miller
• Nitro-Phos Iron & Soil Acidifier
• Ironite
• Hi-Yield Iron Plus
• Any liquid iron/soil acidifier

If you don't see a significant green-up after two weeks, assume you have a nutrient lock-up. The easiest thing to do is apply a soil-activator/microbial treatment to the afflicted areas. Hopefully, if there's a phosphorous lock-up going on, this treatment will help release the right nutrients.

Products you've heard me recommend for such treatments:

• Medina Soil Activator
• Medina Plus
• Lady Bug Terra Tonic
• Soil Mender Foliar Plus

If cost is no object, you can do an an iron treatment and a soil-activator treatment together. I prefer this method: iron first, soil activator second - both on the same day, because I don't want to have to wait around to judge results.

But, what if neither of these treatments works? It could be the dreaded St. Augustine Decline - SAD. We have not discussed this for some time, and frankly there is no cure for it. Some fungicides work a little bit, but none are effective at complete control. (Here's more about SAD.)

But the yellowing could also be the start of Take-All Patch. With TAP, the grass more or less thins out ... we often refer to it as "melting away." But if you catch it early ... in the yellowing stage before the melt ... you can control it with the information HERE.

By the way, if you have a lot of nutgrass in the yellowing areas, this is a harbinger of Take-All Patch.

The last possibility ... something that causes a "yellowing tinge" ... would be Gray Leaf Spot. The timing is way off on that predicament, though. Normally, GLS hits in the spring right after a high-nitrogen fertilizer application is followed by drenching rains. Most people who follow my schedule don't ever get this problem because they use controlled/slow-release fertilizers with ratios like 19-4-10, which is NOT a high-nitrogen fertilizer (something like a 29-3-4). Nevertheless, if GLS needs to be controlled, here's the tip sheet on controlling it.

Randy will be on vacation for the next two weeks. The next GardenLine newsletter will be published July 19.

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