INFLUENCE OF FALL APPLIED 2,4-D AMINE AND MCPA ON COLD HARDINESS AND OTHER AGRONOMIC CHARACTERS OF WINTER WHEAT AND RYE

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Abstract
The effects of 2,4-D and MCPA amine treatments on cold tolerance and other agronomic characters of winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) were studied in controlled environment and field trails. For both species, the level of cold tolerance achieved in controlled environments was reduced following exposure to 2,4-D and MCPA at rates up to 2.24 kg ha−1. In contrast, similar rates of fall applied 2,4-D and MCPA did not affect the cold tolerance of wheat and rye growing in the field. Treatment of plants from different seeding dates indicated that the observed field herbicide tolerance was not influenced by large differences in plant growth stage. Yield and other agronomic characters were also unaffected by fall 2,4-D and MCPA treatment. In contrast, broadleaf weed control was obtained with rates as low as 0.28 kg ha−1 for both herbicides, emphasizing the large safety margin between rates required for effective winter annual weed control and crop tolerance levels. From a practical standpoint, the influence of other management practices, such as delayed seeding, were of much greater importance in winter cereal production than the effects of commerical rates of 2,4-D or MCPA applied in the fall for broadleaf weed control.Key words: Wheat (winter), rye, 2,4-D amine, MCPA amine, cold tolerance