Date: August 10, 2001
Category: Diseases Subject: Bentgrass Dead Spot, Gray Leaf Spot
Dr. Noel Jackson reports the first diagnosis of BENTGRASS DEAD SPOT in
New England for this season. This new disease is apparently restricted
to new (<6 yrs old) bentgrass. Unlike dollar spot, it does not produce
abundant foliar mycelium. Spots generally do not coalesce. Infected leaves
usually are full of tiny black fruiting bodies. Preliminary fungicide
information suggests that Banner (2 oz), Cleary's 3336 (8 oz) + chlorothalonil,
chlorothalonil (4.9 oz + iprodione (5.3 oz) can be used weekly until disease
is controlled. Healing of dead spots can take quite a bit of time. If
you see a few early spots, remove them to prevent spread of spores. If
you are not sure of the diagnosis, send a sample to Dr. Jackson at URI.
If you have a good sample for class, please send a spot or two to me (Gail
Schumann for fall classes. If you are not sure if it's dollar spot or
not, there are two clues: 1) BDS attacks only bentgrass, so if Poa is
affected it's probably dollar spot; 2) put a plug in a plastic bag with
a moist paper towel overnight. Sprinkle a little water on the turf surface.
Close bag, but leave a "bubble" of air over the turf surface.
If you see white mycelium in the morning, esp at the edge of the spot,
it's dollar spot, not BDS.
GRAY LEAF SPOT has been reported on a ryegrass athletic field in Kentucky
this week. If you have perennial ryegrass in lawns, athletic fields, fairways,
etc. watch closely and get an immediate diagnosis from Dr. Jackson at
URI (see Diagnostic section for phone and address). I will report New
England outbreaks as soon as I hear about them. Do not rely on field diagnosis.
If you need to spray right away, take a sample first for confirmation.
Keep in mind that resistance to Heritage and Compass has been documented.
The hot weather should break this afternoon, and it should remain moderate
through next week. Any night below 59 will stop brown patch. Tonight will
stop Pythium. Just a few more hours...Good luck.
