Research Summaries for Paclobutrazol Related Literature
Burch, P.L., Wells, R.H., and Kline, W.N. III. 1996. Red
Maple and Silver Maple Growth Evaluated 10 Years After Application
of Paclobutrazol Tree Growth Regulator. Journal of Arboriculture
22:61-66.
Red maple (Acer rubrum) and silver maple (Acer saccharinum)
trees treated with paclobutrazol produced less biomass resulting
in less pruning time and less chip time as compared to untreated
controls. The authors estimate paclobutrazol treatments can reduce
the amount of biomass removed on red maples and silver maples by
85% and 88% respectively over a ten year period.
Jacobs, K. A., and Berg, L.C. 2000. Inhibition of fungal
pathogens of woody plants by the plant growth regulator paclobutrazol.
Pest Management Science 56:407-412.
Paclobutrazol inhibited the growth of eight common tree pathogens
(Armillaria gallica, Botryosphaeria dothidea, Ceratocystis fagacearum,
Fusarium roseum, Ophiostoma novo-ulmi, Sirococcus clavigignentijuglandacearum,
Sphaeropsis sapinea, Verticillium dahliae) in petri dish assays.
Mycelial growth was inhibited 25-100% depending on the species of
pathogen and fungicidal activity was present at dosages 200 X more
dilute than current label recommended rates for woody landscape
plants. Six species were tested for fungal spore germination and
it was determined that four species exhibited a reduced capacity
for spore germination in comparison to controls.
Redding, K.D., Burch, P.L. and Miller, K.C. 1994. Growth,
Biomass, and Trim/Chip Time Reduction Following Application
of Flurprimidol Tree Growth Regulator. Journal of Arboriculture
20:38-45.
Silver maples (Acer saccharinum) located in Ohio, willow
oak (Quercus phellos) and water oak (Quercus nigra)
in Virginia, and Norway Maple (Acer platanoides) in Pennsylvania
were treated with a tree growth regulator to assess shoot growth,
green biomass production, and actual trim/chip time. Results for
all species across all sites revealed a 63% reduction in shoot elongation,
75% reduction in green biomass, and a 55% reduction in trim/chip
time.
Watson, G.W. 1991. Attaining root:crown balance in landscape
trees. Journal of Arboriculture 17:211-216.
The balance between water and mineral absorption by the roots and
utilization of these resources by the crown is affected by physical
changes to a site as well as physiological changes by the plant.
Transplanting, construction damage, and excessively increasing canopy
size all negatively affect the root:crown balance. Among other arboricultural
practices, paclobutrazol may benefit trees by decreasing the top
growth and stimulating root development.
Watson, G.W. 1996. Tree Root System Enhancement with Paclobutrazol.
Journal of Arboriculture 22:211-217.
Soil injected paclobutrazol was effective in stimulating fine root
development in pin oaks (Quercus palustris) and white oaks
(Q. alba). In soils that do not prohibit root growth, paclobutrazol
may be effective in stabilizing declining trees with insufficient
fine root development.
Watson, G.W. 2000. Tree root system enhancement with paclobutrazol.
In: A. Stokes (ed). The Supporting Roots of Trees and Woody
Plants: Form, Function and Physiology, 131-135. Kluwer Academic
Publishers. Netherlands.
Paclobutrazol treatments stimulated fine root development of established
healthy and chlorotic pin oaks (Quercus palustris). In addition,
analysis of soil core samples taken from the root zones of declining
white oaks (Q. alba) that were treated with paclobutrazol
showed an increase in root density, crown color and overall vigor
three years later. Paclobutrazol increased the length and the root
dry weight of newly transplanted black maples (Acer nigrum).
Zhang, P.G., Sutton, J.C. and Fletcher, R.A. 1993. Paclobutrazol
protects black spruce seedlings against predisposition to gray
mold induced by high temperature and drought. Canadian Journal
of Forestry Research 24:1033-1038.
Basal drench applied paclobutrazol significantly decreased sporulation
incidence and the number of spores produced on needles of Black
spruce (Picea mariana) that were subjected to environemental
stresses conducive for the gray mold pathogen (Botrytis cinerea).
According to the author it was suggested that suppression of the
pathogen was due to pre-stress conditioning of the trees rather
than the fungicidal activity of paclobutrazol.
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