Turfgrass Scouting report: June 30, 2019
Well folks, I hope everyone is having a good season so far. I think in some ways we’ve been lucky so far that we’ve not experienced high temperatures. With how wet the spring was if the temperatures had gotten extreme to quick we would have seen a lot disease issues. Hopefully there will be some good root growth out there now and better grass growing conditions.
Both the maximum and minimum temperatures are now starting to steadily increase. The maximum temperatures have been fluctuating between ~70–90°F, while the minimum temperatures have been fluctuating between ~55–70°F over the last 2 weeks. In comparison to the scouting report soil temperatures have increased to ~70°F. We have had a few more wet days over the last two weeks.
Dollar spot pressure remains high, so if your trying to reduce fungicide applications by extending your reapplication window, I would suggest now is not the time to do so.
A recent study found bi-weekly sand topdressing of golf course fairways reduced the severity of dollar spot by 50%. Please find the manuscript reference and abstract below.
Reference: Green, Thomas O., John N. Rogers, James R. Crum, Joseph M. Vargas, and Thomas A. Nikolai. “Effects of Rolling and Sand Topdressing on Dollar Spot Severity in Fairway Turfgrass.” HortTechnology 1, no. aop (2019): 1–8.
Abstract: “Results suggest that sand topdressing was more consistent at reducing dollar spot (Clarireedia jacksonii) in fairway turfgrass more so than rolling. This practice could be an effective cost-saving alternative to reduce frequent fungicide applications. Research was conducted from 2011 to 2014 on a simulated golf fairway and examined dollar spot severity responses in a mixed-stand of creeping bentgrass (Agrostis stolonifera) and annual bluegrass (Poa annua ssp. reptans) to sand topdressing and rolling. Treatments consisted of biweekly sand topdressing, rolling at three frequencies (one, three, or five times weekly), a control, and three replications. Infection was visually estimated. Sand topdressing significantly (P < 0.05) reduced disease up to 50% at the peak of the dollar spot activity in 2011, 2013, and 2014. Results on the effects of rolling on dollar spot were inconsistent.”
Last week anthracnose popped up in the Chicago area and central Illinois. During my studies, I’ve been taught that anthracnose is a low fertility or stress associated disease. During the 90’s and early 2000’s anthracnose severity seemed less than it is today. My thought process is that during the 90’s and early 2000’s nitrogen rates being applied were higher, then following the recession of 2007/8 nitrogen rates were reduced and we started to experience higher severity of anthracnose. Around the same time Waitea patch became an issue, another low nitrogen associated disease. It should also be noted there are a number of different factors associated with both diseases. However, the comments above are purely my own speculations on why these diseases developed as issues for golf course superintendents (a little philosophizing keeps the day fun!!).
Research conducted at Rutgers University investigated the role topdressing timing plays in anthracnose severity. The research found spring topdressing helps to reduce the amount of summer time topdressing required to suppress anthracnose severity. However, topdressing throughout the summer months is still required on a light but frequent basis for best disease suppression.
Reference: Hempfling, J.W., Clarke, B.B. and Murphy, J.A., 2015. Anthracnose disease on annual bluegrass as influenced by spring and summer topdressing. Crop Science, 55(1), pp.437–443.
Abstract: “Sand topdressing annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] (ABG) turf during the summer (SU) can reduce the severity of anthracnose disease, caused by Colletotrichum cereale Manns, but the effect of spring (SP) topdressing warrants further research. A 2-yr field study evaluated the effect of SP and SU topdressing on anthracnose severity of ABG maintained at 3.2-mm on a sandy loam in North Brunswick, NJ. Factors of SP (0, 1.2, and 2.4 L m−² yr−¹) and SU (0, 0.525, 1.05, 2.1, and 4.2 L m−² yr−¹) topdressing rate were arranged as a 3 × 5 factorial. Increasing SP rate reduced the area under disease progress curve (AUDPC) linearly in both years, whereas increasing SU rate reduced AUDPC linearly in 2009 but quadratically in 2010. Maximum AUDPC reduction was predicted at a lower total topdressing rate (2.4 and 2.63 L m−² yr−¹ during SP and SU, respectively) in 2010 than 2009. Unlike AUDPC data, pooled disease severity data indicated that SP interacted with SU topdressing, and by late 2010, a SU topdressing rate as low as 2.1 L m−² yr−¹ (at the greatest SP rate) maximized disease suppression. However, incorporation of sand applied at 2.1 and 4.2 L m−² yr−¹ was often delayed, resulting in excess sand on the surface, whereas lower SU rates (0.525 and 1.05 L m−² yr−¹) readily incorporated into the turf. This research indicates that SP topdressing can be used to reduce the rate of SU topdressing needed to suppress anthracnose but may not eliminate the need for SU topdressing to maximize disease suppression.”
In another study at Rutgers University investigators noted increased nitrogen resulted in greatest disease suppression. Please find the reference and abstract below.
Reference: Hempfling, J.W., Schmid, C.J., Wang, R., Clarke, B.B. and Murphy, J.A., 2017. Best Management Practices Effects on Anthracnose Disease of Annual Bluegrass. Crop Science, 57(2), pp.602–610.
Abstract: “Increased N fertilization, mowing height, and sand topdressing are management practices that can suppress anthracnose disease of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama; ABG] caused by Colletotrichum cereale Manns. A 3-yr field study evaluated the relative importance and interactions of these factors on anthracnose severity, turfgrass quality, and ball roll distance (BRD) on ABG turf in North Brunswick, NJ. A factorial combination of mowing height (2.3 and 3.2 mm), N fertilization (100 and 200 kg ha−¹ yr−¹), and sand topdressing (46 and 98 Mg ha−¹ yr−¹ in 2012; 37 and 81 Mg ha−¹ yr−¹ during 2013 and 2014) was arranged in a split-split-plot design with four replications. The practice of applying greater N fertilization (200 kg ha−¹) provided the greatest reduction in disease severity and improvement in quality than the practices of higher mowing (3.2 mm) or greater sand topdressing (98 or 81 Mg ha−¹). Combining greater N with higher mowing and greater sand topdressing provided acceptable disease suppression without the use of fungicides during moderate but not severe anthracnose epidemics. Higher mowing often produced unacceptable BRD (<2.9 m) especially when combined with greater N fertilization; whereas, under lower mowing, BRD was acceptable on most observation dates (91–96%) and less influenced by greater N fertilization. Thus, when adjustments in best practices for anthracnose management are needed to enhance BRD; lowering the mowing height will provide that enhancement while not greatly increasing the risk for anthracnose especially when greater N and increased topdressing practices are also employed.”
From an integrated disease management point-of-view, incorporating cultural management practices to suppress anthracnose has been successful.
Thanks go out to Dr. Leah Brilman and DLF-Pickseed for the donation of 007 creeping bentgrass. The seed will be used in future renovations at the Sunshine Course.
For anyone interested Dr. Lee Miller’s most recent disease report can be found at https://turfpath.missouri.edu/reports/2019/06_28_19/.
Well folks with that I’ll say adios, have a great Fourth of July and keep it tight out there!!
Please don’t hesitate to call or email and I will ensure you get a rapid response.
Thanks,
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Bobby Kerr, Ph.D. Director of Turfgrass Programs. Chicago District Golf Association, 11855 Archer Ave, Lemont, IL 60439. C: (312)-519–7940. W: (630)-685–2307.
