Effect of Timing of Winter Weed Control on the Growth of Young Peach Trees under Sod Culture.

Abstract

A census of the weed population by species and their coverage and heights was made periodically over the summer in fruit trees and grapevines to characterize the vegetation of winter annual weeds in sunny orchards (Exp. 1). The timing of herbicide applications on the reduction of competition between winter annuals and the growth of 1-yr-old 'Hikawahakuho' peach (Prunus persica Batsch. var. vulgaris Maxim.) trees was studied (Exp. 2). The competition between those weeds and 4- and 6-yr-old 'Hikawahakuho' peach trees was also examined incorporating various vegetation management practices (Exp. 3). When weed management allowed winter annual weeds to grow freely in young sunny orchards, Vicia angustifolia L. became dominant from March to June, followed by Stellaria media (L.) Villars, and Lamium amplexicaule L. Those winter weeds reduced the overall growth of 1-yr-old peach trees when they were not controlled by May. Growth inhibition of newly developing shoots and fine roots by winter weeds was not as strong as that by summer weeds. Shoot length was reduced significantly in 4-yr-old peach trees but not in 6-yr-old ones. The results indicate that winter weeds need to be controlled by early May to minimize inhibition of peach tree growth.