Here’s what you can do when take all root rot invades your lawn
I’m getting take all root rot questions already, and I know there will be more.
I’m seeing it in lawns as I travel, and I know I’ll see more. This is a disease that doesn’t hide itself well. It screams out for attention.
Take all root rot (TARR), also called take all patch, is a soil-borne fungus that attacks the roots of St. Augustine, also zoysia and even bermudagrass. It kills the roots off, leaving them stubby and dark colored, almost as if white grub worms had been at work, but when you dig you can’t find any grubs.
Afflicted grass pulls loose easily from the soil surface.
But all of that isn’t especially noticeable from above ground. What we do see is bright yellow blades as we look across the turf. Grass isn’t able to take up the nutrients and we see those distracting washes of yellow.
Our first inclination is to reach for the big bag of fertilizer to try to correct it. After all, grass that’s off-color needs nutrients, right? Well, yes, to a degree. But the problem is that this grass just can’t assimilate the nutrients that are already there in the soil, so it’s time to figure the next step.
Take all root rot was first brought to my attention in the 1990s. My friend Dr. Phil Colbaugh, then a research pathologist with the Texas Agricultural Experiment Station of Texas A&M, told me about the fungus and the fact that it was more prevalent in alkaline soils. He was initially prescribing application of a type of organic matter, which he eventually fine-tuned to a 1-inch layer of sphagnum peat moss.
By then I was experiencing TARR in my own lawn. We live in a rural area one mile from any other St. Augustine, so I was puzzled how the apparently “new” disease could have made its way to my turf, but there it was. I tried the peat treatment and it worked splendidly. But it was difficult to apply and expensive as well. Plus, it seemed like a poor use of a valuable natural resource.
Three years ago Phil, by then in retirement, called to tell me that a fungicide (Azoxystrobin) had been given label clearance for use in treating TARR and that it was showing good results. I looked online, and sure enough, southern universities in the St. Augustine zone had all started to recommend it.
The good thing about Azoxystrobin, he told me, is that it actually kills the fungal organism, while the old peat treatment merely suppressed it. So finally we have a means of fighting back at this cool-season disease that seems determined to break out each April and May. We’ve even had it pop up in October one or two times in recent years. And, yes, left untreated, it will weaken and kill the St. Augustine.
The research reports that I’ve read recently encourage us to keep our St. Augustine as healthy as possible. That stands to reason, but it needed to be said. Fertilize the turf with a high-quality product, but don’t overdo it. Keep it moist, but not wet. Mow it regularly at the recommended height of 2 to 2-1/2 inches to keep it low and dense. Be sure the area where it is growing drains well during periods of extended rain. Do everything you can to keep the grass healthy. Take all root rot seems to be much more common in lawns that are allowed to languish.
Other St. Augustine ills
Without wanting to seem too pessimistic about St. Augustine, we probably ought to look ahead to the other problems you may encounter this growing season. Take all root rot will abate as it turns warm, but there are others waiting to take its place.
Gray leaf spot is another fungus that attacks St. Augustine. It causes yellowed patches in the lawn when viewed from 15 or 20 feet back. On closer inspection, however, you’ll see diamond-shaped, gray-brown lesions on the blades, where TARR causes green and yellow striping.
Gray leaf spot often follows applications of nitrogen in fast-release form, and it’s almost always in the hot weather of summer. That’s why I recommend that your second feeding of your St. Augustine be made no later than June 15, and that it be made with a high-quality, slow-release lawn food with upwards of half of its nitrogen in slow-release form. The same Azoxystrobin fungicide will also slow the spread of gray leaf spot.
Chinch bugs show up about the same time as gray leaf spot – as early as late June. They are small pests, about BB-sized, black with irregular white diamonds on their wings. They will always show up in the hottest, sunniest parts of your lawn, and affected grass will look like it’s dry, but irrigation won’t help. You’ll be able to see them if you get down on your hands and knees and part the grass at the boundary of the afflicted area with your fingers. Apply Merit insecticide to control them.
Brown patch is a cool-season disease of the fall. The grass will develop yellow patches 18 to 24 inches in diameter. Affected blades will come loose easily with just gentle tugs. Once again, Azoxystrobin will control it. Avoid nighttime watering as well.
You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 pm and on WBAP 820AM Sunday mornings 8-10 am. Join him at www.neilsperry.com and follow him on Facebook.
