Rainfall Effects Following Herbicidal Treatment of Woody Plants

Abstract

In North Carolina, the shoots of naturally-established, field grown, foliated specimens of turkey oak (Quercus laevis Walt.) and red maple (Acer rubrum L.) were treated in August with aqueous dilutions of three herbicidal products at three rates each. Simulated rainfall was applied at ½ or 1 inch at 5, 15, 60, or 120 min after herbicidal application. Responses measured 10 and 13 months after herbicidal application were percent control of original shoots, percent control of new shoots, shoot height, and number of live stems/plant. Neither the ester nor amine derivatives of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were reduced as to their action on woody plants by the simulated rainfall applied. The action on woody plants of 4-amino-3,5,6-trichloropicolinic acid (picloram) plus 2,4-dichlorophenoxyacetic acid (2,4-D) was markedly reduced by the application of all of the simulated rain treatments at any of the intervals at which they were applied following herbicidal treatment.