This study describes separate methods for injecting growth retardants into herbaceous and woody plants. Bean plants (Phaseolus vulgaris L. ‘Black Valentine’) were treated by injecting growth retardant solutions into the hypocotyl cavity with a syringe. The chemical was subsequently absorbed into the vascular system. Woody California privet (Ligustrum ovalifolium Hassk.) was injected by forcing chemical solution into the vascular system via a predrilled hole. Results with NAA (1-napthalene-acetic acid) and MH (1,2-dihydro-3,6-pyridazinedione) validated the methods by inhibiting growth, respectively. New growth regulators, mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyl]acetamide} and dikegulac (sodium salt of 2,3: 4,6-bis-O-(1-methylethylidene-α-L-xylo-2-hexulofuranosonic acid], inhibited the growth of bean with concentrations of 60 mg/L and 480 mg/L, respectively. Sprout growth of privet was inhibited by 30 mg/L of mefluidide and by 188 mg/L dikegulac.

The growth retardant activity of MBR 18337 {N-[4-(ethylthio)-2-(trifluoromethyl)phenyl]-methanesulfonamide} was determined by injection into bean plants (Phaseolus vulgaris L. ‘Black Valentine’), California privet seedlings (Ligustrum ovalifolium Hassk.), and saplings of white ash (Fraxinus americana L.) and red maple (Acer rubrum L.). Height and leaf expansion of bean were inhibited by 8 μg of MBR 18337 per plant in growth chamber studies. Sprout growth of California privet grown in the greenhouse was inhibited for 92 days by 80 μg of MBR 18337 per tree, and the growth in the field of ash and maple saplings was retarded by 3.2 mg of MBR 18337 per tree for an entire growing season with little injury. Radioassays for 14C-MBR 18337 indicated rapid translocation of 14C-activity in privet from the lower stem to the region of the apical shoot. More than 80% of the MBR 18337 in the xylem and phloem was oxidized within 14 days.