Leaf Spot and Melting Out

David McCall, Associate Professor and Turfgrass Pathologist, and Mike Goatley, Professor and Turfgrass Extension Specialist

Following several days of persistently warm, wet conditions, in late spring/early summer, Virginia’s cool-season grasses will almost always have a rapid burst in disease pressure. These images, above and below of a tall fescue lawn, came from one of our Virginia Cooperative Extension agents in central Virginia, and this followed 4+ days of heavy rain. The diagnosis and recommendations from Drs. Mike Goatley and David McCall follow:

Melting Out Symptoms on Tall Fescue Lawn

Dr. Goatley says: The symptoms point to Leaf Spot that is progressing to the Melting Out phase where the crowns are being killed...i.e. the disease is moving from a cosmetic problem to a more serious concern during this persistently cloudy, extremely wet period. I'd anticipate with the warming temperatures of early summer on tall fescue that Brown Patch is also lurking in the wings, and I suspect a bit of this damage is from that fungus as well. However, most of what I see in these two images is classic leaf spot/melting out symptomology. Let’s bring Dr. McCall into the discussion.

Dr. McCall says: Leaf spot would absolutely be my first guess. This has been on a roll with all of the moisture in late spring across Virginia. As Mike mentioned, brown patch will likely kick in next so if the homeowner is going to treat, they might as well go with something that would take care of both leaf spot and brown patch. I recommend using something with a QoI classification active ingredient (azoxystrobin, fluoxystrobin, or pyraclostrobin). If the homeowner is using a granular product, I would recommend either Headway G or Pillar G, as both have a QoI, plus a DMI fungicide. Both products should be quite effective at suppressing brown patch and leaf spot.