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Dollar Spot

Some Early Disease Activity

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Sorry no pictures for this post, but thought I would share some recent observations. The recent rains and warm night on Friday/Saturday brought out two diseases on annual bluegrass earlier than we typically experience at the research farm in North Brunswick NJ (Hort Farm No. 2).

Saturday morning, our graduate student found nickel- to quarter-sized spots of foliar Pythium on his annual bluegrass plots. Tended to be more spots on his plots with greater N fertility but the disease was also on low N plots. This is the earliest I have experienced foliar Pythium, but the Friday/Saturday nighttime temperature didn’t get much below 65 degrees F, ‘good’ for Pythium.

Also on annual bluegrass, was a slight outbreak of dollar spot on Saturday morning. Dollar spot in April is early but not unheard of in NJ.

You might notice that the pests mentioned have shown up first on annual bluegrass.

Right On Cue: Dollar Spot Disease

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Exactly like Dr. Bruce Clarke teaches, Memorial Day arrives and so does dollar spot disease.

Symptoms appear as round, brown to straw-colored spots approximately the size of a silver dollar. On short cut turf, the spots with advanced damage can become somewhat sunken. At taller cutting heights (greater than 1 inch), the damaged spots are larger and more diffuse.

Highly susceptible grasses will be the first to exhibit symptoms including annual bluegrass, creeping bentgrass (depending on cultivar), and perennial ryegrass. Tall fescue and most Kentucky bluegrasses will be more tolerant of this disease.

Cultural techniques that can suppress dollar spot disease include disruption of dew and guttation water in the morning and increasing N fertility (if it is low). Mowing early in the morning (disruption of dew) should also be helpful.

Creeping bentgrass.
Creeping bentgrass entries in Dr. Stacy Bonos’ evaluation trials that are highly susceptible to dollar spot disease appear in the image foreground.

Dollar Spot Activity Flares Overnight

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The high humidity of last night (28-29 May) caused dollar spot disease to escalate. Until last night, symptoms on unprotected susceptible turf were minor.

The cottony fungal growth (mycelia) of dollar spot, which is easily seen at early morning hours during wet humid weather.

Susceptible grasses grown under low N fertility will typically have [Read more…] about Dollar Spot Activity Flares Overnight