We've got that covered too. Dr. Kaitlyn Bissonnette has the MU nematode laboratory (aka SCN diagnostics) fully staffed and back in operation for assessing nematode populations on golf putting greens or sports fields. If you would like me to also assess the population levels, include a note to them.
The light switch of summer was quickly and forcefully turned on in the last two weeks, with both high day and low nighttime temperatures spiking considerably. Along with these spikes, evapotranspiration (ET) values estimating plant water needs also rose considerably, with short crop ET estimating 0.2 up to 0.25" a day of plant water loss. Much of southern and western MO landed into the first, lowest level of drought intensity as of July 14 - droughtmonitor.unl.edu.
Rain did return for some this week after most of MO had been missed over the previous. Intense storms on Wednesday, July 15 dropped upwards of 2-3" on some parts of NW Missouri, but most other areas, particularly in southern MO are still in a 1-2" deficit for the month.
Forecasts indicate a sustained heat wave, with a significant spike this weekend into the upper 90s (feel like 100+) and the 90+ degree high/70+ degree low painful train extending through much of July. Rainfall chances will also be sporadic. Typical dog days of summer are unfortunately on tap to drag down cool-season turfgrasses.
Rain in the Middle, Dry on the Sides
When the Other Spots Attack
Severe Year for Brown Patch on Tall Fescue
Severe Year for Brown Patch on Tall Fescue
Summer patch has been observed infesting both Kentucky bluegrass and creeping bentgrass roots over the last few days. The two reports, however, may have underlying, predisposing factors for the outbreak that are related to the same issue.
On the golf course putting green, black layer was prominent at about the one-inch mark and extended another inch or so before stopping and resuming to normal disease-free sand. The profile had aerification channels filled with fresh sand and for 20+ year old greens the layering wasn't that significant and the organic matter seemed well distributed. Although summer patch was found prevalent in the roots, the bigger chicken in this case is the black layer. The anaerobic bacteria release hydrogen sulfide gases, and their mere presence indicates a lack of oxygen. The first and most important course of action is (of course) an immediate solid tine venting, which by the way everyone should be doing often to burp greens in this heat! For black layer, a move away from ammonium sulfate and towards nitrate-based sources is also suggested. But the question is why the black layer there in this profile?
The summer patch on the Kentucky bluegrass was most prominent on areas where the tarp water was dumped. Again, excessive moisture leading to summer patch outbreaks and in this case unfortunately accompanied by a high pH water source. However, this site, like the golf course, was on a solid preventive fungicide program geared specifically for summer patch control. No underlying black layer type issues detected here, but again why is the summer patch present when researched and effective fungicides were applied? Why is this chicken still running around the farm and not on the dinner plate?
In both these cases, the lack of enough post-application irrigation may be involved as an underlying factor. In the golf course case, the greens, like many, are on a program with wetting agents to facilitate more uniform soil moisture and to combat localized dry spot. The wetting agent may not have had enough post application irrigation to push it through and cause a uniform wetting front through the profile. The stagnant wetting agent would presumably hold the water in place and not allow for penetration deeper in the profile and out of the system. Dr. Micah Woods of the Asian Turfgrass Center recently posted a tweet pointing out the lack of research in how "penetrant" vs "retaining" wetting agents affect soil moisture. Without this data, my assertion is that the more post-application irrigation the better, with 1/8" being a minimum. My observation is that considerably more damage is caused by wetting agents not being pushed far enough, rather than being pushed too far. I also am not a fan of half-rate wetting agent applications, but that is another story.
In the Kentucky bluegrass case, enough post-application irrigation may not have been applied to push the fungicide far enough into the soil profile to get to the target zone of pathogen infection. Research at North Carolina State (https://turfpathology.ces.ncsu.edu/2019/02/where-did-your-fungicide-go/) consistently demonstrates that post-application irrigation on creeping bentgrass putting greens is vital to moving fungicides targeting soil-borne pathogens into the root zone. Even in a sand-based root zone, a quarter inch of irrigation is necessary to move many of these systemic fungicides down to an area where they can be effective. Also don't forget most of these fungicides are apoplastic and move systemically upwards in the plant. So as far down as you put them, is as far down as they are going to go.
Post Application Irrigation
Perhaps a bit more water than you might think.
Last but not least, an eighth to a quarter inch of irrigation is a lot of water. It's easy to get fooled and believe that it is a miniscule amount, particularly on a rain gauge when trying to figure out where the bottom of the meniscus is. The math, however, tells a different story – an acre inch of water = 27,154 gallons of water and translated to our standard area of measurement is 623 gallons of water/1000 sq ft. See the chart below to see how this breaks out and the extraordinary amount of water this is. This fact struck me the first time I watered in applications for a research study by hand with Dr. Randy Kane at the Chicago District Golf Association. Over an eighth of an inch on a 50 sq ft plot took some time and resulted in a wet surface.
My advice is if you don't know exactly how much irrigation you are putting out in inches by the amount of time that you set, grab a few rain gauges or irrigation audit collection cups and get to work. Many of the times I've heard are in the 4-5 minute range for PAI. Even with part-circle heads this is concerning, considering that one less pass of the water stream may make the difference in whether or not the product is watered in sufficiently. Perhaps laying an egg on that product's purpose.