RESPONSE OF REPEATED 2,4-D SPRAYS ON THE NODE DIAMETER, INTERNODE LENGTH AND CARBOHYDRATES IN THE CANES AND COLD HARDINESS OF CONCORD GRAPE BUDS

Abstract

Field grown high and low vigor Vitis labruscana cv, Concord grapevines were sprayed with 2,4-D amine in concentrations of 0, 2.5, 10 and 25 ppmw at 1st leaf; 1st and 3rd leaf; 1st, 3rd and 5th leaf and 1st, 3rd, 5th and 7th leaf stages of vine growth for two consecutive years. Cane and bud samples were collected for determining node diameter, internode length, carbohydrates in the canes, and T50 of buds. Data on yield and vegetable growth were also collected. There were significant differences among treatments in the node diameter and cold hardiness of buds (T50) both in high and low vigor vines. Repeated applications of 2,4-D reduced the cane diameter significantly but the carbohydrates in the canes were not affected. When 2,4-D symptoms were severe in July, yields were reduced by as much as 85%, but there was slight or no reduction in yield when symptoms were not severe.