Rapid Blight in California: Regional Observations Frank P. Wong Cooperative Extension Specialist University of California Arizona Rapid Blight Summit Cactus and Pine GCSA Superstition Springs Golf Course January 24, 2007

Rapid Blight

First found in 1995 in Santa Ana on annual bluegrass in southern California  found on perennial ryegrass in 1999 from Arizona  found on rough bluegrass in 2000 from South Carolina Caused by Labyrinthula terrestris  A marine slime mold  Rare case of a marine organism jumping to terrestrial environments

Rapid Blight Spores

Geographic and Temporal Distribution of Rapid Blight in California

Distribution of Rapid Blight in the US

Rapid Blight in California 177 positive diagnoses 170 on Poa annua 2 on Rough Bluegrass 2 on Creeping Bentgrass 3 on Perennial Ryegress

California Rapid Blight Almost all diagnoses were from annual bluegrass putting greens Affected rough bluegrass was found in two locations on greens in the Coachella Valley Affected creeping bentgrass greens only found in two Los Angeles locations Affected perennial ryegrass from greens surrounds and fairways

Timing of attack on Poa greens 2001 Data PACE-PTRI

2003 Rapid Blight (n=66)

2004 Rapid Blight (n=46)

2005 Rapid Blight (n=26)

2006 Rapid Blight (n=39)

Summary ’03-’06: Rapid Blight Timing on P. annua

Salt Effects on Rapid Blight Incidence

Soil Salinity for Annual Bluegrass Greens Samples RB (-), 84 RB (+)

Soil Salinity and Rapid Blight Negative samples  mean: 1.69 dS/m  median: 1.61 dS/m  range: 1.07 to 6.2 dS/m Positive samples  mean: 3.13 dS/m  median: 2.96 dS/m  range: 1.07 to 9.1 dS/m  Most often seen above 2.2 dS/m

TDS-meter Monitoring Meter Actual EC

High Low Salinity measurements for Annual Bluegrass are best made in the root zone, no more than 1-inch deep

Anecdotal Observations for Rapid Blight Management on Annual Bluegrass

Rapid Blight Appears worst on older annual bluegrass greens with push up construction  Lack of water infiltration through soil profile Courses with poor quality water more commonly affected  Salty well water worse than effluent  Effluent worse than potable

Rapid Blight Appears more frequently under warm temperatures vs very hot  Pathogen appears to grow between 70 and 90F  Increased irrigation under hot weather  Increased transpiration by annual bluegrass in moderate temperatures

Rapid Blight Fungicide applications appear to arrest epidemics, but they return if the salt is not leached out  7 – 10 days of activity (or less) without leaching  Management solely by fungicide applications not recommended Resistance to QoIs (Insignia, Compass)?  Likely if fungicides are repeatedly used  Tank mix with mancozeb  Don’t use them as the only management option

Questions???? Contact Info plantpathology.ucr.edu