Fireblightinfectionconditions-Cougarblightmodel

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Return to Apple list for Easthampton MA
Weather data for Easthampton MA. Forecast values begin August 3, 2017
This table shows estimates of RELATIVE daily fire blight blossom infection risk based on weather conditions. Rating criteria are from the CougarBlight 2010 model developed in Washington and Oregon by Dr. Timothy J. Smith.
ABSOLUTE risk depends on the amount of fire blight bacteria in the area, the number and age of open flowers, tree age (1-5 years old most vulnerable), cultivar and rootstock susceptibility. Ratings are for flowers that have NOT received an application of streptomycin or other fire blight suppression material. You can use the daily heat unit values between application date and a subsequent wetting event to estimate heat unit accumulaiton for flowers that received antibiotic treatment. Relative infection risk may be overstated for first few days of bloom because fire blight bacteria may not have been distributed to open flowers. Individual cutltivars may start or finish bloom a day or two earlier or later than the range of open blossom dates shown. Gray shading indicates dates when most trees will have lost open blossoms, but late blooming cultivars,"straggler" or secondary bloom (e.g. Cortland and Golden Delicious), or young trees may still have open flowers and be susceptible to blossom blight. Infection of a few late blooms can provide a foothold for fire blight to colonize an orchard.
Fireblight infection can occur without rain if there is wetting caused by dew. If there are enough heat units for infection but no rain, if leaves are expected to be wet for 2 or more hours, then infection risk is reported with a "dew risk" label. Infection potential on"dew risk" days is not well understood. Infection potential may increase with high relative humidty prior to and during infection events, and be reduced by an extended period of low relative humidity.
Fire blight blossom infection risk varies with block history. If you do not know orchard history, use category II as default assumption.
I = No active fire blight within 1 mile of the orchard in last two years. Requires 500 799 heat units for HIGH rating, 800 999 for EXTREME!, and 1000+ for EXCEPTIONAL!
II = Fire blight was present within 1 mile of the orchard within last 2 years, but not currently active in the area this year.
Requires 200 349 heat units for HIGH rating, 350 499 for EXTREME!, and 500+ for EXCEPTIONAL!

III = Active fire blight cankers within 1 mile of the orchard this year.
Requires 100 199 heat units for HIGH rating, 200 299 for EXTREME!, and 300+ for EXCEPTIONAL!
If blossom infection occurred April 30, then blossom blight would be noticeable by May 24, and shoot blight by June 11.
Open blossom dates for common apple cultivars.
"Date" is from 8am to 8am the next day, not midnight to midnight.
Cumulative Heat Units (single day units)
Inches Rain,
&
Leaf Wet Hours
8am to 8am next day
I - No active FB within one mile of the orchard in last two years II - FB active within one mile of orchard in last two years, but not this year III - Fire blight currently active within one mile of orchard. Date blossom blight (and shoot blight) symptoms would be obvious if infection occurred
possible early cultivar
King Bloom: April 28
172 HU (172)
0.0'', 5 hrs
Caution
(dew risk)
Caution
(dew risk)
HIGH
(Dew risk)
May 21, (June 10)
McIntosh King Bloom:
Sat, April 29
322 HU (149)
0.0'', 0 hrs
Caution
(if wetting)
High
(if wetting)
Exceptional!
(if wetting)
May 24, (June 11)
Sun, April 30 323 HU (2)
0.15'', 9 hrs
Caution HIGH EXCEPTIONAL! May 24, (June 11)
Mon, May 1 329 HU (6)
0.77'', 9 hrs
Caution HIGH EXCEPTIONAL! May 24, (June 11)
Tue, May 2 170 HU (14)
0.11'', 7 hrs
Caution Caution HIGH May 24, (June 11)
Wed, May 3 24 HU (3)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
Thu, May 4 29 HU (7)
0.05'', 4 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Fri, May 5 25 HU (2)
1.35'', 24 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Sat, May 6 24 HU (12)
0.13'', 14 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Sun, May 7 23 HU (3)
0.03'', 9 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Mon, May 8 16 HU (0)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
Tue, May 9 15 HU (0)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
Wed, May 10 5 HU (2)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
Thu, May 11 7 HU (5)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
Fri, May 12 12 HU (5)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Unlikely (lack of heat & wetting)  
McIntosh 95% Petal Fall
on Sat, May 13
13 HU (1)
1.32'', 18 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Sun, May 14 12 HU (2)
0.27'', 15 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
McIntosh 100% Petal Fall
on Mon, May 15
15 HU (7)
0.07'', 5 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
McIntosh 100% Petal Fall
on Mon, May 15
15 HU (7)
0.07'', 5 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Wed, May 17 627 HU (504)
0.0'', 0 hrs
High
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 4, (June 13)
Late Cultivar Petal Fall
on Thu, May 18
1257 HU (632)
0.22'', 11 hrs
EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL! June 9, (June 14)
Fri, May 19 1611 HU (361)
0.0'', 2 hrs
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 10, (June 15)
Sat, May 20 1516 HU (20)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 10, (June 16)
Sun, May 21 1032 HU (20)
0.10'', 6 hrs
EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL! June 11, (June 17)
Mon, May 22 403 HU (3)
0.15'', 21 hrs
Caution EXTREME! EXCEPTIONAL! June 11, (June 17)
Tue, May 23 63 HU (20)
0.0'', 9 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Wed, May 24 76 HU (32)
0.0'', 3 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Thu, May 25 59 HU (3)
1.34'', 24 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Fri, May 26 62 HU (7)
0.24'', 24 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Sat, May 27 64 HU (21)
0.0'', 4 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Sun, May 28 61 HU (30)
0.0'', 0 hrs
Very low (lack of heat & wetting) Low (lack of heat & wetting) Caution
(if wetting)
 
Mon, May 29 61 HU (3)
0.15'', 21 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Tue, May 30 62 HU (8)
0.01'', 16 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Wed, May 31 66 HU (25)
0.59'', 22 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Thu, June 1 97 HU (61)
0.0'', 3 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Fri, June 2 112 HU (19)
0.0'', 0 hrs
Very low (lack of heat & wetting) Caution
(If wetting)
High
(if wetting)
June 13, (June 19)
Sat, June 3 123 HU (18)
0.0'', 0 hrs
Very low (lack of heat & wetting) Caution
(If wetting)
High
(if wetting)
June 13, (June 20)
Sun, June 4 121 HU (22)
0.46'', 15 hrs
Low
(lack of heat)
Caution HIGH June 13, (June 20)
Mon, June 5 66 HU (6)
0.80'', 24 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Tue, June 6 47 HU (0)
1.05'', 24 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Wed, June 7 64 HU (36)
0.0'', 9 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Thu, June 8 112 HU (71)
0.0'', 2 hrs
Low
(lack of heat)
Caution
(dew risk)
HIGH
(Dew risk)
June 14, (June 21)
Fri, June 9 214 HU (108)
0.0'', 0 hrs
Caution
(if wetting)
High
(if wetting)
Extreme!
(if wetting)
June 15, (June 22)
Sat, June 10 548 HU (334)
0.0'', 0 hrs
High
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 17, (June 23)
Sun, June 11 1093 HU (580)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 18, (June 24)
Mon, June 12 1701 HU (679)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 19, (June 25)
Tue, June 13 2230 HU (636)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 21, (June 28)
Wed, June 14 2110 HU (214)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 22, (June 29)
Thu, June 15 1614 HU (85)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 22, (June 30)
Fri, June 16 955 HU (20)
0.43'', 18 hrs
EXTREME! EXCEPTIONAL! EXCEPTIONAL! June 23, (June 30)