Effects of 2,4,5-T During the Approach of Woody Plant Dormancy

Abstract

The shoots of naturally established specimens of turkey oak (Quercus laevis Walt.) and red maple (Acer rubrum L.) were treated under conditions of approaching dormancy. Aqueous sprays of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were applied as foliar treatments to the point of run-off at 2-week intervals beginning September 13 and continuing until three applications had been made for turkey oak and five had been made for red maple. Three experiments were conducted for turkey oak and two for red maple. Application rates were 2, 4, 8, and 16 lb of 2,4,5-T aehg of spray solution except that the 16-1b rate was deleted for turkey oak. Ester and amine derivatives were evaluated. Responses measured 9, 12, and 24 months after initiation of the experiments were percent control of original shoots, percent control of new shoots, shoot height, and number of live stems/plant. The average estimated control of original shoots of turkey oak and red maple increased from 42 to 54% as the application date was advanced from September 13 to October 11. The average height of the plants treated September 13 considering all evaluation dates was 3.4 ft compared to 2.6 ft for treatment made 4 weeks later. The results suggest two seasonal peaks in the response of some woody plants to foliar treatments of 2,4,5-T and that herbicidal effectiveness can be enhanced by application at the onset of senescence and dormancy.