Date: July 18, 2001
Category: Diseases Subject: Summer Diseases on Lawns and Golf Course Turf
Some more humid weather with higher temperatures, especially at night,
which will enhance certain diseases.
IN LAWNS that are overwatered, watered at times that keep the leaves
moist, or in areas with poor air movement and/or poor drainage, BROWN
PATCH can quickly become active. Disease is more severe in lush, over-fertilized
turf and in perennial ryegrass lawns. Luckily, this is a foliar disease
that rarely kills plants. The brown patches will generally recover. Night
temperatures below 59 F are the same as a fungicide for stopping fungal
activity. Fungicides are not generally recommended for this disease. If
lawns are a little low in available N, DOLLAR SPOT or RED THREAD may be
active in moist weather. The grass symptoms can be very similar, but careful
observation in morning dew or on a rainy day will reveal the fungi that
cause these diseases: white mycelium for DOLLAR SPOT and red threads or
pink puffs of spores for RED THREAD. Both generally respond well to small
doses of N and any activities that promote good grass growth and minimal
leaf wetness.
ON GOLF COURSES, ANTHRACNOSE is the most troublesome problem at the moment.
This coincides with the natural time of Poa annua decline due to various
environmental stresses and the plant's natural life cycle. Anthracnose
is a stress disease associated with sand topdressing, low mowing heights,
compaction, shallow roots, insufficient N and water. Fungicides can be
quite effective at stopping the fungus, but you must also deal with the
stress factors to effect recovery. Plants that are all brown and/or with
infected crowns are unlikely to recover at all. Plants that are still
green in the center are more likely to recover, but it will be slow unless
the stresses that led to anthracnose are reduced. The fungus produces
abundant spores in affected areas that are easily spread to new areas.
Wash mowers before leaving diseased areas to reduce this spread. SUMMER
PATCH is also present in some Poa annua. This, too, is a stress
disease, but it is a root disease that is not spread by mowers. BOTH summer
patch and anthracnose will respond well to any activities that promote
deeper roots and an improved root environment. Consider skipping the clean-up
pass periodically and/or temporarily raising mowing height. Hydroject
or otherwise open up compacted areas as weather allows. Because bentgrass
is less likely to be infected, try overseeding damaged areas.
