rapid blight in california: regional observations frank p. wong cooperative extension specialist...
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Rapid Blight in California:Regional Observations
Frank P. WongCooperative Extension Specialist University of CaliforniaArizona Rapid Blight Summit Cactus and Pine GCSASuperstition Springs Golf CourseJanuary 24, 2007
Rapid BlightRapid Blight
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
2003-06 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
0
2
4
6
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14
Jan
Feb Mar
AprM
ay Jun
July
AugSep
tOct
NovDec
# o
f d
iag
no
ses
Timing of attack on Poa greens2001 Data PACE-PTRI
2003 Rapid Blight (n=66)
0
2
4
6
8
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12
14
Jan
Feb
Mar
ch AprM
ay Jun Ju
lAug Sep Oct
NovDec
Rap
id b
lig
ht
hit
s
0
0.5
1
1.5
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3
3.5
Inch
es o
f ra
in
2004 Rapid Blight (n=46)
0
2
4
6
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12
14
Jan
Feb
Mar
ch AprM
ay Jun Ju
lAug Sep Oct
NovDec
Rap
id b
lig
ht
hit
s
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Inch
es o
f ra
in
2005 Rapid Blight (n=26)
0
2
4
6
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14
Jan
Feb
Mar
ch AprM
ay Jun Ju
lAug Sep Oct
NovDec
Rap
id b
lig
ht
hit
s
0
1
2
3
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6
Inch
es o
f ra
in
2006 Rapid Blight (n=39)
0
2
4
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14
Jan
Feb
Mar
ch AprM
ay Jun Ju
lAug Sep Oct
NovDec
Rap
id b
lig
ht
hit
s
0
0.5
1
1.5
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Inch
es o
f ra
in
Summary ’03-’06: Rapid Blight Timing on P. annua
0%
5%
10%
15%
20%
25%
Jan Feb March Apr May Jun Jul Aug Sep Oct Nov Dec
Dia
gn
os
es
Salt Effects on Rapid Blight Incidence
Soil Salinity for Annual Bluegrass Greens Samples 2004273 RB (-), 84 RB (+)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Negative
Positive0
10
20
30
40
Fre
qu
ency
Soil Salinity (dS/m)
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 MonitoringMeterMeter Actual ECActual EC
0.00.0 0.80.8
0.10.1 1.11.1
0.20.2 1.31.3
0.30.3 1.61.6
0.40.4 1.91.9
0.50.5 2.22.2
0.60.6 2.42.4
0.70.7 2.72.7
0.80.8 3.03.0
0.90.9 3.23.2
1.01.0 3.53.5
1.11.1 3.83.8
1.21.2 4.04.0
HighHigh
LowLow
Salinity measurements for Salinity measurements for Annual Bluegrass are best Annual Bluegrass are best made in the root zone, no more made in the root zone, no more than 1-inch deepthan 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
