Mark your Calendars - University of Arkansas & University Missouri Virtual Turfgrass Field Day - August 12th! More details forthcoming.
Cool, Welcome Start to July
July is set to operate inversely to June, coming in with mild temperatures and leaving with scorchers. Through the first half of July, temperatures throughout the region have been 1 - 3 degrees below normal, a welcome event since July is historically our hottest month. Oddly, Missouri has actually been cooler than North Dakota, which is dealing with crop losses due to that region's historic heat and drought. Unfortunately temperatures are set to flip back to "normal" here, with excessive heat and humidity forecasted for this weekend, next week and the foreseeable future. Time to restock the wet towels in the ice buckets.
The Spigot Was Stuck On
For most of the region, except the KC region, July has continued with the rainy pattern that rounded out June. At the MU research farm, we received no rain from May 28 - June 18, and since have tallied nearly 16.5 inches, with almost a quarter of that occurring on June 25th alone. This has echoed throughout July as much of the state is 2 - 5 inches above normal for the month with more than a week to go. All of that rain is slated to stop, with dry conditions occurring much of this week and forecasted to continue over the next 10 - 14 days. Wet, soggy ground conditions combined with the heat will set up miserable humidity this weekend, and high temperature stress for both humans and cool season turfgrass. Kansas City has issued an excessive temperature warning for the weekend; a trend that may continue as July rounds the corner into August.
Another Pattern Flip Expected
Low N diseases rampant
Nitrogen - I sung this song to start June (click here to see previous report), and I'll sing it again. If you've been impacted by the deluge of recent rainfall, there is a better than good chance the turfgrass could use a small boost of nitrogen. On sand-based putting greens, this is especially true, and the reason for constant rates of spoon feeding throughout the summer. Anthracnose on putting greens is still routinely observed in the lab and is a sign of low nitrogen. Know how much nitrogen has been put down and react to the conditions if necessary. On lawns, the need might not be as high, but dollar spot on Kentucky bluegrass is the worst I've observed in years here and it's no coincidence. A small shot (0.25 lb N/1000 sq ft) may help in this case, particularly on irrigated lawns. All this being said, cool season turfgrasses may shut down growth with impending high temperature, and perhaps drought, stress. So don't overdo it now.
Pythium root diseases on putting greens As the temperature flipped, samples have come in this week with significant Pythium root rot infection. As noted below, these infections may have been helped along by another soil dwelling critter. Curatively, Koban/Terrazole is recommended as an opening salvo, followed three days later by a high-rate Segway application. Of course, all of these applications should be watered in with at least 1/8 and perhaps closer to 0.2 inch of post application irrigation.
Masked chafer beetles in STL:
High populations noticed in the region.
Beetles Make Grubs: Although not an entomologist, I can safely make this obvious statement. The beetles that constitute a major portion of the turfgrass infesting grub population, masked chafers and green June beetles, have also been obvious over the last few weeks. In front of Waters Hall, green June beetles (Cotinis nitida) are very evidently flying and buzzing about the lawn. In St. Louis, a golf superintendent has also been noticing an extreme abundance of masked chafers (Cyclocephala spp.) as shown above. Although Japanese beetles are thought to be the major contributor to our August -September grub populations, the masked chafer may be the bigger culprit. Living as grubs for several years, this may be a boom year for the masked chafer, while the Japanese beetle populations so far have been a bust. In discussion with Dr. Kevin Rice, MU field crop entomologist, increasing variability in insect populations have been occurring over the last 10 years as climate patterns change, making forecasting and predicting insect damage more difficult. This beetle boom could signal a corresponding boom in grub issues later this season, so be on guard.
Nematodes in Golf Putting Greens
NOTE: Nematodes have not been found to be an issue on higher cut turfgrass grown on native soils in Missouri.
Over the past few days, several golf putting green samples have been submitted to the diagnostic clinic, that were then turned over the SCN nematode analysis lab. Four of these samples within the last two days had high population levels of plant parasitic nematodes, including ring nematode (1,494 per 100 cc of soil) and lance nematode (363, 666 (yikes), and 1,080 per 100 cc of soil). All of these are over the MU threshold of 1,000 ring nematodes per 100 cc of soil and 200 lance nematodes per 100 cc of soil. These high populations are early for lance nematodes, which in our experience normally spike in late August - early October. All of these samples, also not coincidentally, had other diseases present such as anthracnose, Pythium root rot and summer patch.
Ring nematodes (Criconemella spp.) are often observed in association with bentgrass roots, but are not often seen at high population levels. They also are considered "wimpy" nematodes with smaller stylets and feeding habits that result in less root damage. Therefore, high population levels are needed to result in symptoms and the intervention threshold is higher. Interestingly, the affected putting green was recently established and on a strong fungicide program but no nematicide application. Ring nematodes are fairly easily controlled with fluopyram (Indemnify) or other watered-in nematicides.
As many may know, we are currently conducting research on the lance nematode (Hoplolaimus spp.) which should indicate the importance and control difficulty of this species. Lance is a big nematode that feeds both outside the root as an ectoparasite and "swims" inside the root tissue wreaking havoc as an endoparasite. Our research is the subject of Asa McCurdy's M.S. thesis, and since April he has been sampling 10 sites throughout the region to determine the abundance and vertical distribution of the lance nematode. With this information, we hope to further refine and develop control strategies…
Which implies that control is difficult. Abamectin (Divanem) will control lance nematodes if it touches them. However, lance nematodes can reside inside roots and abamectin ties up in the organic matter and thatch layer strongly. Applying this insecticides requires tank mixing with a surfactant or penetrant, with uncertainty on which one best does the job in distributing it through the profile. Applying in the early morning dew, and immediately irrigating it in with 0.2-0.25" of post application irrigation is suggested. In addition to abamectin, a new product containing heat killed Burkholderia bacteria (Zelto) has also been introduced to the market, and has reports of anecdotal effectiveness by several superintendents. We are testing the product now on a lance nematode hotspot. Hopefully other tools will become available in the near future to help deal with high lance nematode populations.
In all of the 349 samples collected in 2018, 34% were above the 200 lance per 100 cc of soil threshold, and 17% were above 500 per 100 cc! In 2019, the populations were lower and 2020 is still a missing data point. Like the 2018 spike and the masked chafer, perhaps lance nematodes will cycle on in 2021 and be a significant issue again on putting greens. If you have putting green areas that don't respond to water or fertility, consider sending a sample in for both disease and nematode analysis.