Frost Injury on Apple
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Frost injury can affect flowers or small fruit. Injury to ovaries of flowers occurs when temperatures drop below critical levels. Browning is apparent almost as soon as flowers thaw. Most fruit with seeds killed by frost drop from the tree prematurely. Frost rings develop on fruit when ice forms beneath the fruit epidermis, separating the epidermis from the fruit flesh. Cork cells form in response, resulting in russeting. Frost rings typically occur at the calyx end of the fruit. Pumpkin fruit symptoms are another manifestation of severe cold injury to outer portions of fruit. Affected fruit are unmarketable except for use in cider.
Flower with frost injury (left) and uninjured flower (right).
(Photo: John Strang, University of Kentucky)
Frost ring.
(Photo: Nicole Ward Gauthier, University of Kentucky)
Pumpkin apple symptom of freeze injury.
(Photo: John Strang, University of Kentucky)
Management:
- Proper site selection (good air drainage)
- Reduce orchard freezing using equipment such as wind machines (air inversion), overhead irrigation (sprinklers), and a supplemental heat source
