Retardation of tree growth by injection of plant growth regulators

Abstract

Previously topped American sycamore (Platanus occidentalis L .), cottonwood (Populus deltoides Bartr. ex Marsh), water oak (Quercus nigra L .), and bigleaf maple (Acer macrophyllum Pursh) trees were injected with aqueous solutions of maleic hydrazide or dikegulac-sodium in April-June, 1979 at various locations around the United States. Measurements made later in the autumn showed that dikegulac-sodium reduced sprout regrowth in all four species, whereas maleic hydrazide was only effective in controlling regrowth of American sycamore and cottonwood. The effects of dikegulac persisted through the second growing season . Significant variability was observed among treated trees and must be reduced in order to achieve consistent growth responses from an application of growth retardants .

Regrowth Response of London Plane Injected with Dikegulac at Different Stages of Tree Development

“…Deciduous trees, if treated with MH at bud-break showed excessive phytotoxicity (Sachs, 1969). In a study with injected growth retardants, the greatest effect was reported for trees treated during the spring (Domir et al, 1982).…”

“…Studies carried out during the last several years have shown that application of growth-regulating chemicals can provide an effective alternative to mechanical pruning (Domir, 1978). Investigations conducted with aqueous growth regulators suggest existence of significant regrowth variability among tree species pressure injected with any concentration of a plant growthregulating chemical (Domir et al, 1982; Roberts et al, 1 979). There may be several reasons for lack of uniform regrowth among chemically treated trees, including heredity, physiological vigor of the tree canopy, size of the tree, uneven distribution of chemical among limbs of trees, and stress influences such as air-pollutants and moisture deficits (Domir, 1982;Domir, 1981 and1983).…”