Another Wild April Roller Coaster
April was again a roller coaster ride of temperatures and precipitation, in what is beginning to feel normal. Overall, April temperatures in the state should average a degree or two below normal for the month, but a whole lot of story resides in the near average. A one-week temperature swing of 27°F and lower temps and snow on April 20 to an 87°F high yesterday is somehow starting to feel normal. This being stated, several low temperature records were reached throughout Missouri last week, and our fruit farmers certainly will feel the long-lasting effects with frost damage on peaches, apples, and several other crops. Warm season turfgrasses were halted in their tracks, and although my scouting earlier this week didn't observe any significant injury on our research farm, we may need to wait and see how bounce back occurs later into May.
Precipitation has varied throughout the state as shown below, with the overserved being in the middle of the state, while thirsty soils surround on all sides. Today and tomorrow a significant system should even that out more than a bit, as southern areas of the state are in the bullseye with flood watches and potential for severe storms. Heading into the first week of May, warmer than normal temperatures are expected along with steady chances of rainfall. Turfgrass should be steady growing towards summer and out of an up and down spring now, with diseases and other issues soon to be following suit.
Warm May Start with Rainfall Chances in 6-10 Day Forecast
Dollar Spot Arrives on Bentgrass Putting Green Research Plots
Dollar Spot Arrives on Research Plots: Active dollar spot has arrived pretty much as expected these last few days on our untreated research plots. This is the first outbreak we've heard of in the region, which stands to reason. These plots are on our infamous "disease green", which is 'Penncross', had a few overwintering scars, was inoculated annually, down in a hole and normally stays wet. All of which indicates an indicator plot.
To coincide with our outbreak, I received an email alert this morning from the GDD tracker of high dollar spot potential in St. Louis, and noted considerable spikes in our chart tracking the Smith-Kerns model probability throughout the state (see Threshold Charts here). We've had a few blips in the model prior and this recent spike seems to be the environmental straw that broke through. On extremely susceptible areas, the 20% threshold may seem a bit high but it's important to take into account microclimate when assessing the implementation of the model on your own site. The weather data that goes into the model presumably doesn't factor in those tucked in greens with higher humidity, so use the model as a guide that shakes hands with your on-site experience.
Red Thread & Net Blotch: These two diseases were observed in a tall fescue/Kentucky bluegrass mix on a sod farm in southern MO this week. Eerily, both diseases were also observed this same week last year – (see April 30, 2020 report here). Net blotch, in particular, can be prevalent on younger tall fescue stands and is most often seen on sod farms. For both diseases, maintaining adequate, and not overdoing, nitrogen fertility and reducing leaf wetness will reduce disease levels considerably with warmer temperatures helping the plant grow out of the disease. Even in the most severe cases, a single fungicide application, presumably of a QoI fungicide to also get ahead of brown patch, is often all that is needed for adequate control.
Calling all the Troops
As we flip the calendar to May, golf superintendents realize the battle is on the horizon. All of the famous "Lord of the Rings" pre-battle scenes come to mind. Fires are lit on mountain tops and the Horn of Gondor is blown (perhaps analogous to aerification practices), to call in the troops to help ward off the enemy hordes. In terms of golf greens management, the countrymen that need gathering are putting green roots.
Key Time for Preventive Soilborne Disease Control on Putting Greens
In the spirit of protecting our convoy of bentgrass roots from early disease marauders, the second watered-in fungicide application targeting fairy ring and other root diseases should be planned soon. The first of the split application should've been made when the 55°F soil temperature threshold was reached in early April. In the last week, several have inquired if the 21-day interval should be strictly adhered to, especially since the hard freeze and snow event last week. In my research, the split applications were separated by a 28-day interval, so allowing for that sliding scale between 21 and 28 days (or even 30 if necessary) should be an adequate preventive strategy. In other words, there should be a little leeway in timing the second application akin to the split applications of crabgrass preemergents.
Since fungicides to ward off fairy ring and others are in the DMI (or QoI or SDHI) chemistry, they are not effective nor will guard against another enemy, Pythium root rot. With average soil temperatures rising to 60°F and frequent rainfall in the forecast, consider starting prevention of Pythium root rot soon on putting greens with a history of this disease. Segway (a.i. cyazofamid) has been found consistently to provide the best prevention and control of Pythium root rot, and should be viewed as a good starting point and cornerstone of a preventive fungicide program.
As a last note, make sure to water in these preventive fungicide applications with at least 0.125" and up to 0.25" of post-application irrigation. The question is often asked "which fungicide application doesn't get watered in during the spring on bentgrass greens?". Prior to dollar spot pressure, my response is none. These fungicides won't do much to help with the Pythium (Smaug) fairy ring (orcs), take-all patch (Balrog), and summer patch (Gollum) invasion if they don't reach the battlefield of your rootzone.