Different weather patterns associated with fall are conducive to different issues in the landscape. Although fall isn’t the only time we would see powdery mildew, it is definitely more likely for outbreaks to be visible.
Weather conditions have been as steady as a roller coaster here in the Great Lakes region, which is pretty typical and expected for this time of the year. Last week, we had heavy fog several mornings, some rainfall, and overall cooler weather, in other words, perfect conditions for powdery mildew on turf.
Powdery mildew, or Blumeria graminis, is a foliar disease of turf that is easy to see, which may spur phone calls for diagnostics and control suggestions.
It appears as white or gray flecking on the upper leaf surface, and in more severe cases, it could appear as the plant has been dusted with flour in irregular patches.
These infections are more common in shady areas, which gives us a hint as to some of the control strategies. The pathogen which overwinters in dormant turf or leaf litter as cleistothecia is more active during cooler periods and on turf that is slower growing. Other factors that can influence progression include poor air circulation and excess nitrogen fertility.
The good thing is that generally powdery mildew is considered an aesthetic issue rather than being highly destructive. Mild outbreaks are often ignored, but in cases where it is severe, yellowing and turf thinning can occur. This is unlike some of the powdery mildew pathogens which infect certain ornamentals and food crops, which can cause damage along with yield loss.
It is common on cucurbit or gourd family which includes cucumbers, watermelon, pumpkin, squash, and others. This, however, is a different pathogen, usually Podosphaera xanthii. Left untreated, the pathogen that infects turfgrasses will not move to other plants.
As stated earlier, powdery mildew on turf is fairly innocuous, so truthfully no real action is needed.
If it is considered intolerable on a particular property, then there are some steps to eliminate it. Pruning trees and shrubs to improve sunlight penetration and airflow should be enough in most cases to prevent future outbreaks. Where a more aggressive approach is favored, fungicides in the DMI family tend to be the most effective. These fungicides largely end in "azole," for instance propiconazole. The few that don’t follow that rule include fenarimol, which is Rubigan, triadimefon, marketed under the name Bayleton, or leading the way in effectiveness, myclobutanil. High visibility areas, which historically are hit with powdery mildew, can be treated on a preventative basis.
Make sure to read and follow all label instructions, and feel free to reach out to the Ewing Technical Services Team with any questions.