Regrowth Reduction in American Elm and Sycamore by Growth Regulator Injection1

Abstract

Abstract Water solutions of commercial formulations of growth regulators were pressure-injected into the trunks of topped American elm (Ulmus americana L.) trees in June to evaluate their ability to reduce sprout regrowth. Regrowth was significantly reduced by methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol), N-[4-methyl-3-[[(trifluoromethyl)sulfonyl]amino] = phenyl]acetamide (fluoridamid), l,2-dihydro-3,6-pyridazine-dione (maleic hydrazide), succinic acid,2,2-dimethylhydrazide (daminozide) and 2,3,5-triiodobenzoic acid (TIBA); α-cyclopropyl-α-(4-methoxypenyl)-5-pyrimidine = methanol (ancymidol) and (2-chloroethyl)trimethyl-ammonium chloride (chlormequat) were ineffective. Some undesirable effects on the tree and foliage were observed. Maleic hydrazide (MH) and daminozide (SADH) were selected for additional field tests at 3 concentration levels on topped American elm and American sycamore (Platanus occidentalis L.). Regrowth was significantly reduced and foliage condition was acceptable for the high concentration of SADH and the low concentration of MH. Successive measurements in both experiments showed that sprout regrowth was reduced by an amount equivalent to at least 1 year of growth during the first 2 seasons following treatment.