Date: June 26, 2001
Category: Diseases Subject: Summer Patch, Anthracnose
SUMMER PATCH has been diagnosed on annual bluegrass (Poa annua)
for the first time this season. The recent heavy rains and warm temperatures
seem to have caused the problem. It generally occurs in stressed (low
mowing heights), compacted areas. It is a disease caused by a root-infecting
fungus very similar to take-all patch which occurs on bentgrass. If it
is caught in the early stages, fungicide applications that are watered
in to deliver the fungicide to the roots and crowns are most effective.
If the roots are badly diseased, they will probably be unable to absorb
the fungicide. Stress relief is also important. Try to rotate traffic
patterns with frequent cup movement; raise mowing heights; syringe turf
when hot and dry.
ANTHRACNOSE is also active on annual bluegrass, and symptoms can sometimes
be confused with those of summer patch. If anthracnose is in the foliar
stage, you can usually see the tiny tufts of hairlike black setae on the
leaves, especially with a field microscope. This stage responds well to
stress relief and fungicide. The basal rot/crown rot stage of anthracnose
results in charcoal black fungal structures in the base of the plant which
often leads to plant death. Anthracnose is most often observed on annual
bluegrass, but it can also infect bentgrass. Unlike summer patch, which
is a root disease, the anthracnose fungus produces abundant spores that
can be spread by feet and equipment.
