Fireblightinfectionconditions-Cougarblightmodel

Background Information for this page
Return to Apple list for Easthampton MA
Weather data for Easthampton MA. Forecast values begin September 18, 2018
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 May 12, then blossom blight would be noticeable by May 26, and shoot blight by June 3.
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: May 7
22 HU (22)
0.0'', 7 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
McIntosh King Bloom:
Tue, May 8
69 HU (47)
0.0'', 2 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Wed, May 9 184 HU (115)
0.0'', 0 hrs
Caution
(if wetting)
Caution
(If wetting)
High
(if wetting)
May 25, (June 2)
Thu, May 10 207 HU (23)
0.0'', 0 hrs
Caution
(if wetting)
High
(if wetting)
Extreme!
(if wetting)
May 26, (June 3)
Fri, May 11 198 HU (12)
0.0'', 0 hrs
Caution
(if wetting)
Caution
(If wetting)
High
(if wetting)
May 26, (June 3)
Sat, May 12 151 HU (0)
0.23'', 22 hrs
Caution Caution HIGH May 26, (June 3)
Sun, May 13 40 HU (5)
0.0'', 4 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Mon, May 14 62 HU (45)
0.0'', 4 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Tue, May 15 155 HU (105)
0.98'', 24 hrs
Caution Caution HIGH May 28, (June 8)
Wed, May 16 168 HU (13)
0.0'', 9 hrs
Caution
(dew risk)
Caution
(dew risk)
HIGH
(Dew risk)
May 29, (June 8)
McIntosh 95% Petal Fall
on Thu, May 17
227 HU (64)
0.0'', 5 hrs
Caution
(dew risk)
HIGH
(Dew risk)
EXTREME!
(Dew Risk)
May 29, (June 9)
McIntosh 100% Petal Fall
on Fri, May 18
193 HU (11)
0.0'', 0 hrs
Caution
(if wetting)
Caution
(If wetting)
High
(if wetting)
May 29, (June 9)
Sat, May 19 95 HU (6)
0.53'', 23 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution  
Sun, May 20 153 HU (71)
0.08'', 24 hrs
Caution Caution HIGH May 30, (June 10)
Mon, May 21 182 HU (93)
0.0'', 1 hrs
Caution
(dew risk)
Caution
(dew risk)
HIGH
(Dew risk)
May 31, (June 11)
Late Cultivar Petal Fall
on Tue, May 22
181 HU (10)
0.09'', 20 hrs
Caution Caution HIGH May 31, (June 12)
Wed, May 23 401 HU (226)
0.0'', 3 hrs
Caution
(dew risk)
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
June 1, (June 13)
Thu, May 24 459 HU (129)
0.0'', 0 hrs
Caution
(if wetting)
Extreme!
(if wetting)
Exceptional!
(if wetting)
June 1, (June 13)
Fri, May 25 773 HU (407)
0.0'', 0 hrs
High
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 1, (June 13)
Sat, May 26 1247 HU (484)
0.0'', 0 hrs
Exceptional!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 7, (June 17)
Sun, May 27 1024 HU (3)
0.28'', 21 hrs
EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL! June 7, (June 17)
Mon, May 28 912 HU (18)
0.0'', 14 hrs
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 8, (June 17)
Tue, May 29 902 HU (397)
0.0'', 9 hrs
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 9, (June 18)
Wed, May 30 642 HU (224)
0.0'', 3 hrs
HIGH
(Dew risk)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 11, (June 19)
Thu, May 31 800 HU (161)
0.0'', 6 hrs
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 12, (June 20)
Fri, June 1 992 HU (209)
0.03'', 24 hrs
EXTREME! EXCEPTIONAL! EXCEPTIONAL! June 14, (June 21)
Sat, June 2 906 HU (311)
0.0'', 3 hrs
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 16, (June 22)
Sun, June 3 703 HU (22)
0.47'', 6 hrs
HIGH EXCEPTIONAL! EXCEPTIONAL! June 16, (June 23)
Mon, June 4 546 HU (3)
0.34'', 24 hrs
HIGH EXCEPTIONAL! EXCEPTIONAL! June 16, (June 23)
Tue, June 5 345 HU (9)
0.05'', 21 hrs
Caution HIGH EXCEPTIONAL! June 16, (June 24)
Wed, June 6 50 HU (16)
0.0'', 8 hrs
Low
(lack of heat)
Low
(lack of heat)
Unlikely
(lack of heat)
 
Thu, June 7 56 HU (28)
0.0'', 8 hrs
Low
(lack of heat)
Low
(lack of heat)
Caution
(if wetting)
 
Fri, June 8 229 HU (177)
0.0'', 8 hrs
Caution
(dew risk)
HIGH
(Dew risk)
EXTREME!
(Dew Risk)
June 18, (June 26)
Sat, June 9 379 HU (158)
0.0'', 0 hrs
Caution
(if wetting)
Extreme!
(if wetting)
Exceptional!
(if wetting)
June 18, (June 27)
Sun, June 10 415 HU (52)
0.0'', 0 hrs
Caution
(if wetting)
Extreme!
(if wetting)
Exceptional!
(if wetting)
June 18, (June 27)
Mon, June 11 428 HU (42)
0.0'', 0 hrs
Caution
(if wetting)
Extreme!
(if wetting)
Exceptional!
(if wetting)
June 19, (June 28)
Tue, June 12 390 HU (138)
0.0'', 0 hrs
Caution
(if wetting)
Extreme!
(if wetting)
Exceptional!
(if wetting)
June 20, (June 29)
Wed, June 13 298 HU (65)
0.01'', 3 hrs
Caution HIGH EXTREME! June 21, (June 29)
Thu, June 14 331 HU (85)
0.03'', 3 hrs
Caution HIGH EXCEPTIONAL! June 22, (June 30)
Fri, June 15 310 HU (22)
0.02'', 14 hrs
Caution HIGH EXCEPTIONAL! June 22, (June 30)
Sat, June 16 457 HU (285)
0.0'', 1 hrs
Caution
(dew risk)
EXTREME!
(Dew Risk)
EXCEPTIONAL!
(DEW RISK)
June 24, (July 1)
Sun, June 17 838 HU (446)
0.0'', 0 hrs
Extreme!
(if wetting)
Exceptional!
(if wetting)
Exceptional!
(if wetting)
June 26, (July 1)
Mon, June 18 1273 HU (521)
1.02'', 15 hrs
EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL! June 27, (July 2)
Tue, June 19 1528 HU (277)
0.0'', 1 hrs
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 28, (July 3)
Wed, June 20 1400 HU (157)
0.0'', 5 hrs
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 29, (July 3)
Thu, June 21 1208 HU (254)
0.0'', 2 hrs
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
EXCEPTIONAL!
(DEW RISK)
June 30, (July 4)
Fri, June 22 811 HU (124)
0.02'', 6 hrs
EXTREME! EXCEPTIONAL! EXCEPTIONAL! June 30, (July 4)
Sat, June 23 546 HU (12)
0.01'', 18 hrs
HIGH EXCEPTIONAL! EXCEPTIONAL! June 30, (July 4)
Sun, June 24 494 HU (105)
1.37'', 24 hrs
Caution EXTREME! EXCEPTIONAL! July 1, (July 5)