Apples Uncategorized

The Horrid F Word: Frost

Critical temperatures, frost mitigation strategies and frost assessment tools for apples

The Horrid F Word: Frost

Erika DeBrouwer, Tree Fruit Specialist, OMAFRA

Some recent concerns about temperature drops have popped up in conversation with growers across the province. This “hot” topic is an opportunity to review critical temperatures, frost mitigation strategies and frost damage assessments.

Critical Temperatures

Apples
Silver
Tip
Green
Tip
½ inch
Green
Tight
Cluster
First
Pink
Full
Pink
First
Bloom
Full
Bloom
Post
Bloom
Old temp
-8.9
-8.9
-5.6
-2.8
-2.8
-2.2
-2.2
-1.7
-1.7
10% kill
-9.4
-7.8
-5.0
-2.8
-2.2
-2.2
-2.2
-2.2
-2.2
90% kill
-16.7
-12.2
-9.4
-6.1
-4.4
-3.9
-3.9
-3.9
-3.9
This chart also shows the temperature that will kill 10 % and 90 % of normal fruit buds. These numbers were taken from Washington (WSU), Michigan (MSU) and North Carolina (NCS) Extension Bulletins. Apple – WSU EB0913

Frost Mitigation and Assessment Resources

Erika DeBrouwer
Erika DeBrouwer

Tree Fruit Specialist, OMAFRA

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