An Evaluation of the Efficacy of Tree Growth Regulators Paclobutrazol, Flurprimidol, Dikegulac, and Uniconazole for Utility Line Clearance    (View PDF)

Geoffrey P. Arron, Sally de Becker, Harrison A. Stubbs, and Eugenia W. Szeto

Abstract: A multi-year field program was conducted in California and Nevada to determine the efficacy of tree growth regulators (TGRs). At 37 sites, trees were trimmed and treated with paclobutrazol, flurprimidol, dikegulac or uniconazole by trunk injection, tree implants, or bark banding. Tree growth was determined over a period of 1-4 years for 12 common West Coast species. Growth was determined by measuring increase in tree height. At most sites that were not compromised during the study, the TGRs had no detectable effect on growth. Inhibition of growth was observed over 4 years at one site with London plane (Platanus acerifolia) trunkinjected with uniconazole, at one site with big leaf maple (Acer macrophyllum) trunk-injected with uniconazole, and over 2 years at one site with Chinese elm {Ulmus parvifoWa) trunkinjected with paclobutrazol or uniconazole. Trunk injections and bark banding of flurprimidol inhibited the growth of blue gum {Eucalyptus globulus) over 2 years at one site. There was a lack of consistency in the effects observed; for example, the growth of London plane was inhibited at only one of eight sites. Possible explanations for the low level of effectiveness and lack of consistency include site variability, tree water relations, and hole spacing. Problems were experienced while conducting this large-scale research effort under field conditions. Factors that contributed to a low level of effectiveness and a lack of consistency need to be addressed to improve the cost-effectiveness of the product formulations evaluated.

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https://doi.org/10.48044/jauf.1997.002