Freeze injury in wheat impacts management options
Heading – Zadoks scale 51-59. Most symptoms of freeze injury at this stage are similar to those of earlier growth stages – sterility, leaf burn and stem lesions. The most apparent symptom is chlorosis or bleaching of awn tips. White-tipped awns usually indicate that floral parts have been injured. Awn tips may have a purple cast before turning white. A light-green or white freeze ring may encircle the stem below the head several days after exposure to freezing temperatures. This ring marks the juncture of the stem and flag leaf at the time of the freeze.
Anthesis – Zadoks scale 61-69. Flowering stage is most sensitive to freeze injury. Light freezes at this stage will result in some amount of injury. Usually light freezes at this stage will result in the appearance of more random damage than at other stages. More severe freezes usually cause the entire head to be sterile. Awns of damaged plants will bend to nearly 90 degree angles from the rachis as they mature.
Milk and Dough – Zadoks 71-89. Freeze injury can occur in grain during the milk and dough stages. Usually grain will grow to normal size but then produce light, shriveled grain at maturity. Cereals frozen at milk stage often shatter easily at maturity and germination percentage is usually reduced as a result of the freeze injury. Cereal kernels frozen during the dough stage will have slightly reduced test weights and appear shriveled. Seed germination may be reduced.