Summer stress and diseases

HOT HOT HOT

We've been cooking over the past week.

We are not as bad as Oklahoma. Just reading Damon's post made me break into a sweat, both with the thought of those high temperatures AND the thought of the number of samples he's dealing with. It hasn't been quite that extreme just a bit north, where I am located. But, this current week has been nasty, with more 100+ on the way.

Localized dry spot:

This photo was sent in with a subject line that said “Help!!!”

While I am not a fan of diagnosing based only by photo, the pattern made me suspect localized dry spot (hydrophobic soils) and I suggested that they do the “droplet test” which is described HERE. Indeed, that was the problem. A wetting agent will be useful, but unfortunately the turf itself will not be able to recover very well until these extreme temperatures go away… and that could take awhile.

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Brown patch in creeping bentgrass:

Hot and humid, with high night-time lows = optimal conditions for brown patch. It’s active in greens, fairways, and lawns (fescue).

Dollar spot, in an unsprayed fairway area (creeping bent)

I've also seen some anthracnose in the past few days.

Stress stress stress, why a putting green is like a toddler, and localized dry spot

We've had a stretch of hot weather, high humidity, and very high night-time lows. On Monday and Tuesday I had about half a dozen conversations which started with a superintendent saying "everything looked fine Friday, and by Monday it was in a tailspin."

Root problems in putting greens are common this week. If I only had 1.5 inches of roots, I’d be hurtin’, too:

In turf, and in other plants, all the soaking rains have damaged the root systems and now that it is turning hot, it does not take much to push putting greens over the edge. I asked Dr. Jack Fry to give us some pointers on the tricky balance of water management. You can find his comments HERE.

Just scroll down a little bit. That's where you'll learn how putting greens are like toddlers.

Along with compromised rootzones, hydrophobic soils/localized dry spot can sneak up fast in weather like this and cause wide-spread damage in a short time.

Check out the photo below:

The upper inch or so of the profile is fine–the water drops were absorbed instantly and you can see how the soil is wet. And, from 2-inches down is okay too. Unfortunately, there is a stubborn layer of hydrophobic soil from about 1 to 2 inches down. I put the water droplets there, took the photos, then went to work on some other samples. When I glanced over again 30 minutes later, they still had not been absorbed.

If you have known hot spots of hydrophobic soils it is critical for you to keep an eye on them this week, and as long as the heat continues. Get a soil probe and use it. When you water, take some plugs out and make sure the water is actually getting down where it needs to go. Use a wetting agent, and water it in, following all label instructions.

In hot, dry conditions it’s dangerous to aerify, but if we get a stretch of cooler days, you could use solid tines.

localized dry spot

Tribute to golf course dogs:

I am going to start this week by stating that golf course dogs are some of the best dogs around. I met another one yesterday who was the sweetest thing, a black lab. I think dogs love riding in golf course utility carts even more than they like riding around in pickup trucks. I'm not the only one smitten. I met a superintendent once where the dog was "technically, an employee of the parks department" for chasing geese. I think he was pretty taken with her, because he said that if he changed jobs, the dog might mysteriously disappear with him.

Okay, onto more serious matters.

Localized dry spot:

I had a putting green sample come in the other day where the turf was wilty. There were 4 cup-cutter plugs. When I picked up the first one, I noticed that the sand felt absolutely powder-dry on my fingers. This can indicate hydrophobic soil (water-repellent soil), otherwise called localized dry spot (LDS).

I did the old trick of placing some water drops on the soil and seeing if they wicked in. They did NOT wick in—they just sat there. As I read online somewhere, putting water droplets on normal soil is like putting it on normal paper—the drops get wicked in. Putting droplets on hydrophobic soil is like putting them on wax paper—the drops just sit there beaded up.

I examined the other 3 plugs. One was fine—the sand felt wet, and the water drops wicked in fast. With the other two plugs, parts of the profile were okay, but parts were hydrophobic. Hydrophobic conditions are usually in the top one inch of the soil, but it can be variable. In one plug, the top 1-inch was fine and the lower 1-2 inch was hydrophobic. One of the photos below shows drops beading up in the 1-2 inch range, whereas drops applied to the upper 1-inch wicked in.

LDS has been associated with the decomposition of organic matter, where the sand becomes coated with hydrophobic molecules. This been associated with fungal growth—some fungi produce and secrete hydrophobic chemicals. In particular, fairy ring fungi can produce hydrophobic chemicals, leading to the most damaging types of necrotic rings, but LDS is not always associated with fairy rings. This particular green did have some fairy ring issues, but NOT in the sites where the plugs were taken. There could be a correlation, but it is hard to say.

Wetting agents can help to move water into hydrophobic areas and to evenly distribute the moisture. Be careful, though, as some products can cause phytotoxicity under some conditions. Read the label carefully.

Water droplets wicked in on top, but not in the 1-2 inch range

3 drops sit there, not wicking in:

Snow mold:

I was glad to see Jim's postings about snow mold. As a Wisconsin native, I'm familiar with the regions where he's doing his work. In fact, while visiting my parents in March (they live in Madison, WI, not too far from the turf research center and the University Ridge course where Jim does some work) I stumbled across some snow mold. See, there's a hiking trail that runs through the woods at U Ridge and connects with a regional trail called the Ice Age trail. My parents and I were having a lovely walk, then I got distracted by the snow mold and couldn't help but stop, hunt for sclerotia, then teach my mom and dad to hunt for sclerotia.

Then, we came out of the woods and I found some guys spraying. I strolled over and said, "So, what are you guys spraying?" I could see the look of skepticism in his eyes, and you can imagine his point of view. It's a little unusual to have a woman you've never met come walking out of the woods in March in Wisconsin and ask what you are spraying. So, I quickly followed with, "I'm a turf pathologist, and I know Jim Kerns." With introductions taken care of, I had a nice converation with the superintendent, Aron Hogden (Hi Aron, if you are reading this!)