The lower Midwest experienced extended periods and above normal amounts of precipitation, in addition to unseasonable mild temperatures in June. The result was a dramatic entrance by the usual suspects in terms of turf disease outbreaks. Here are a few of my observations and opinions as of the All-Star break.
Dollar spot–Few, if any, outbreaks appeared on putting greens as supers are careful to provide ample protection to the most critical playing surfaces. Issues occurred on fairways (as always) where succumbing to temptation to conserve fungicide early (mid-May, so not that early) in the season often results in outbreaks that won’t go away. Beyond that, holding back on the first critical fungicide application allows for extraordinary pathogen population build-up. Remedial application of site-specific fungicides to a raging epidemic will accelerate the shift towards fungicide resistance. I recommend tank mixing any site-specific product with a multi-site compound such as chlorothalonil or fluazinam (Secure).
Brown patch–The period from June 12-Jun 23 marked an extended period of weather favorable for brown patch infection and disease development. Again, putting greens remained protected, but symptoms appeared on many tee boxes and fairways. Fortunately, once cooler drier weather arrives, turf thinned by brown patch infection recovers to near-original density within a week or so. We were lucky this year, because a period of four consecutive days of cool dry weather is rare for July in the lower Midwest. Obvious brown patch symptoms on June 20 were clearly recovering by July 5 (Figure 1). Based on samples brought to my attention during late June, brown patch was particularly severe in residential turf (tall fescue, including turf-type tall fescue, is quite susceptible to infection) and many athletic fields.
Anthracnose – The wet weather in June also favored anthracnose infection. Older decaying leaves near the crown are the prime targets. I observed more than a few instances of the beginning stages of basal anthracnose in samples received in mid-June. As Poa annua begins its natural summer senescence, I would expect accelerated turf decline, especially if an extended heat wave descends upon our region. Creeping bentgrass also may show signs of anthracnose, but that usually indicates that unseen stress (root infection of various sorts) is predisposing plants to infection.
What’s next? The wet spring provided ample moisture for infection by pathogens that cause summer patch, take all patch, and Pythium root dysfunction. The consequences of root infection will be noticeable with the first spell of stressful weather. Implementing cultural practices that reduce stress will lessen the severity of these outbreaks. Acidovorax kept a very low profile in 2014. Maybe supers recognize the problem, and understand that damage (if any) is largely cosmetic and brief? Therefore, there was no hysteria regarding this reluctant pathogen that behaves like no other. We’ll soon learn what the second half of 2015 has in store.