Apples

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

With the recent weather taking a turn (cold to hot to cool) and with how fast apples have progressed, 2023 has really been testing growers. This week temperatures are dropping, making it important 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

Tree Fruit Specialist, OMAFRA

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