Beryl sparks disease activity; Brown patch/Pythium combo on tall fescue; Anthracnose pressure intensifies; Waitea/Rhizoctonia patches form on Poa; Field day next week.
Purdue Turfgrass and Landscape Field Day – Next Tuesday, July 16th!
The Purdue Turf and Landscape Field Day is next week on Tuesday. We will have a large number of topics ranging from cultural practices, pest management, drone use, the impact of legislation changes, and landscape issues. See the agenda below and click the link above for more information. Advance registration and payment are closed, so if not pre-registered walk on in and register on site. Hope to see you there.
Weather
The major weather news story of early July was Hurricane Beryl, whose tropical storm remnants blew through and rained on much of the western part of the state along with central Illinois and Missouri. The Daniel Turfgrass Research Center received a little above 3 inches of rain from the event, and many areas went from drought parched to saturated and flooded quickly. Storm clouds depressed early July temperatures and kept them mild, but nonetheless the strong kick of moisture has jump started a high period of disease pressure throughout the region. Lawns that were experiencing drought symptoms previously have experienced some measure of relief, but the heavy disturbed, clay soil left in most lawn situations likely won’t hold much water in reserve. In addition, root systems are still compromised from the wet spring, so unless steady rains ensue its likely drought symptoms will recur quickly.
After a weekend and early week kick of high heat and humidity, forecasts indicate a marked cool down starting mid next week. This cool down will likely temper disease activity driven by Beryl and the snap in high temperatures, but the fuse has likely been lit from here through the rest of the summer season. Rainfall chances are slightly above normal for the southern portion of IN through Missouri, with typical low summer confidence on when and if pop up storms occur.
Beryl’s Potential Impact
Former hurricane Beryl was a record breaker. It was the third earliest Atlantic major hurricane, the earliest to reach Category 4 and 5, and the easternmost hurricane to form in June in the Atlantic. Beryl was also the strongest hurricane by wind speed in both June and July, the only storm to spend 4.5 days as a major hurricane, and the first tropical storm to intensify in the Atlantic Basin in June. While the U.S. midsection didn’t feel the unfortunate brunt of the hurricane like coastal Texas, the storm’s long history contributes to understanding how the tropical storm effects carried well into the middle of the country and even into Vermont and Maine.
At the Daniel Center, we have seen a strong uptick in disease activity this week since Beryl, and if you were in the path of the storm, the infusion of rain and prolonged tropical humidity is likely to have lasting effects the rest of this season. As noted below, Pythium blight is now very active on tall fescue and Kentucky bluegrass and has no problems shaking hands with brown patch. Pythium root rot on high organic matter or poorly draining greens may also be expected if prevention isn’t in place. Black layer on putting greens and perhaps even sports fields, should be prevented by restricting sulfur applications and switching away from ammonium sulfate as a nitrogen source during the summer. Last but not least, scouting for gray leaf spot on perennial ryegrass and tall fescue should occur earlier, with more intent and farther north this year than previous, as tropical storm winds could have supplanted southern borne spores farther into the country’s interior.
Brown Patch + Pythium Tag Team Tall Fescue
Brown patch was already active, but the infusion of rain and humidity unleashed a spark for Pythium blight to joint the party on turf type tall fescue this past week. Both diseases have been observed in the same leaf section, and it’s clear they are acting as a one-two punch towards decline. In ground irrigation systems should obviously not be running now in the hopes of reducing leaf wetness duration and predisposition to these two diseases. Applications of a strobilurin fungicide are recommended to mitigate brown patch, and this chemistry which includes azoxystrobin (i.e. Heritage), pyraclostrobin (i.e. Insignia) and fluoxastrobin (i.e. Fame) also has some preventive effects on Pythium blight. If tall fescue is declining rapidly, apply these fungicides curatively and if they don’t result in control a follow up with a Pythium specific fungicide such as picarbutrazox (i.e. Serata), cyazofamid (i.e. Segway), mefenoxam (i.e. Subdue) or similar. If Kentucky bluegrass is the main species, Pythium, dollar spot or summer patch is more likely to be the major contributor to disease than brown patch.
Waitea Patch on Poa annua putting greens
A new patch disease on our Poa annua research green and from a putting green sample submission just south of Indy popped up in time for the 4th of July fireworks. All signs at this point indicate the disease is Waitea or brown ring patch, which is closely related to diseases such as brown patch caused by other Rhizoctonia spp. Apart from yellow patch, brown patch and other similar diseases, rings often appear scalloped at their edges instead of a uniform patch. The disease is enhanced by low fertility, so a slight bump in nitrogen is suggested for this disease along with anthracnose noted below. Some of the same fungicides effective for brown patch are also effective for Waitea patch, including azoxystrobin, fludioxonil, flutolanil and others, but the disease is not controlled by thiophanate-methyl. Waitea patch can occur, but is more rare on creeping bentgrass greens.
Anthracnose Pressure Dives Deep
An uptick in anthracnose severity on Poa annua and also sporadically on creeping bentgrass has also been observed in the past week. Anthracnose symptoms are characterized by splotchy, irregular yellow, brown or rust colored areas of decline. The pathogen (Colletotrichum cereale) is ubiquitous and a constant feeder on senescing leaves and thatch material normal in the life cycle of any turfgrass plant. This disease is closely tied to stress, and can be mitigated by raising mowing heights, increasing nitrogen levels and protecting the crown with routine topdressing. Anthracnose is also commonly found on dead and decaying leaves from higher mowed turfgrass, but is never the real cause of decline in higher cut turf. On greens, however, where the stress level is maxed at 11 out of 10, anthracnose can cause decline quickly, particularly if it moves from foliage down into the crown of the plant, in a form known as basal rot.
Considering the close tie of anthracnose with low nitrogen, next week’s cool down may be best greeted with a small uptick in nitrogen fertility at sites that have had a history of the disease. Fungicide control should be focused on prevention, which is much more effective than curative control. Due to resistance issues, do not rely on the strobilurin, QoI, or benzimidazole fungicides for control. Newly developed “cool” DMI fungicides such as difenconazole (Briskway) mefentrifluconazole (Maxtima), and prothioconazole (Densicor) are effective, good rotational partners and can be applied during the summer without the risk of excess plant growth regulation and phytotoxicity from older DMI chemistries.
Turfgrass Pathology Program Impact Survey
Follow this link or scan QR code above to access the survey.
Lee Miller
Extension Turfgrass Pathologist – Purdue University
Follow on Twitter: @purdueturfpath