Select a title from the list below to see an abstract of the article. For information about ordering reprints of complete articles, contact ISA at (217) 355-9411 or isa@isa-arbor.com.
Countersinking for Tree Bolts
by E. Thomas Smiley
Abstract. When installing eyebolts and brace rods, the practice
of countersinking into the xylem tissue using a chisel is common. This
study was developed to assess an alternative method of cutting countersinks
and to determine which method has the lower potential for introducing decay.
It was determined that seating the washer on the bark rather than countersinking
into the xylem produced the lowest levels of discolored wood and the lowest
amounts of callus growth over washers. Data from this study support the
recommendation that countersinking into the xylem be discontinued.
Effects of Periodical Cicada Ovipositional
Injury on Woody Plants
by Fredric Miller and Webster Crowley
Abstract. The long-term effect of oviposition by the female periodical
cicadas Magicicada septendecim and M. cassini (Homoptera: Cicadidae)
was examined on woody plants in landscape plantings at The Morton Arboretum
in northeastern Illinois following the 1991-1993 growing seasons. A minimum
branch diameter of approximately 5 mm appears to be a critical factor in
ovipositional activity. Plants with stout branching habits do not appear
to be suitable for oviposition. The percent canopy flagging, as a function
of the number of wounds per branch, may not be an accurate measurement
of ovipositional damage. Young trees with stem diameters or main scaffold
branches with diameters between 5 and 10 mm may experience significant
damage to the main trunk, resulting in breakage and significant growth
loss. Larger plant material does not appear to be significantly affected
by ovipositional damage, but it does result in a minor natural pruning
event.
Surface Energy Balance Affects
Gas Exchange of Three Shrub Species
by Thayne Montague, Roger Kjelgren, and Larry Rupp
Abstract. We investigated the energy balance of vegetative and
nonvegetative surfaces and gas exchange for 3 shrub species growing over
each surface. During a 1-week period, incoming short-wave radiation, surface
and soil temperature, and soil heat flux for turf and pine-bark mulch surfaces
were gathered. Air temperature and relative humidity at 2 heights over
each surface were also measured. Mulch surface and air temperatures were
warmer and soil temperature below mulch was cooler than turf throughout
each day. Relative humidity varied with height above turf, but each height
was comparable over mulch. For the majority of each day, soil heat flux
below turf was greater than mulch. Dawn-to-dusk measurements of stomatal
conductance, leaf temperature, and water loss for containerized skunkbush
sumac (Rhus trilobata), spreading euonymus (Euonymus kiautschovicus
'Manhattan'), and redosier dogwood (Cornus sericea) were measured.
Shrubs in mulch had higher leaf temperatures and greater leaf-to-air vapor
pressure differences than shrubs in turf. Rhus trilobata had greater
stomatal conductance and water loss in turf than mulch. However, for E.
kiautschovicus and C. sericea, there were no differences in
stomatal conductance or water loss between surface treatments. Midday photosynthetic
rate was generally greatest for shrubs over turf. Shrub gas exchange differed
according to how stomata responded to the leaf-to-air vapor pressure difference
over each surface.
Genetic Engineering of Sexual
Sterility in Shade Trees
by Amy M. Brunner, Rozi Mohamed, Richard Meilan, Lorraine A. Sheppard,
William H. Rottman, and Steven H. Strauss
Abstract. Shade trees unable to produce floral tissues, or that
produce only nonreproductive floral organs such as petals, are desirable
for a number of reasons. They can reduce the need to clean flower and fruit
litter, eliminate hazards from large and fleshy fruits on walks, and lessen
allergenic pollen production. Research in herbaceous species has established
that introduction of gene constructs created by recombinant DNA technology
provides an effective means to manipulate flowers without deleterious effects
on vegetative growth. Though not yet demonstrated in trees, this approach
will likely be successful in both angiosperms and gymnosperms because genes
that control reproductive development are similar in sequence and function
among diverse plant species. Key to the practical application of genetically
engineered sterility to shade trees, however, is the development of efficient
gene transfer and vegetative propagation systems to deliver engineered,
sterile trees to the marketplace; these systems are in place for a limited
number of species. We discuss the rationale for sexual sterility in arboriculture,
methods for genetic engineering of sterility, our progress in engineering
sterility in poplars, and the current status of transformation and propagation
methods for some common shade tree genera.
Allelopathy as an Inhibition Factor
in Ornamental Tree Growth: Implications from the Literature
by Timothy A. Chick and J. James Kielbaso
Abstract. Allelopathy is the process whereby plants produce toxins
that limit the growth of other plant species. Forest ecology and agronomy
research has dealt with this phenomenon for some time, but there is a dearth
of inquiry about allelopathy in ornamental and shade trees. A review of
the literature suggests that herbaceous ground-cover toxins may interfere
with nutrient uptake by damaging or destroying root cells, root hairs,
and mycorrhizae. Soil texture appears to be a determinant in the extent
of damage. Trees on poorly drained soils may be severely damaged, whereas
those on well-drained sites may be less affected. Allelopathic factors
interact with competitive and environmental factors. Cultural treatments,
such as mulching and herbiciding, reduce allelopathic effects as well as
competition and environmental stresses. Allelopathic mitigation enhances
nutrient uptake, reducing the need for tree fertilization.
Urban/Community Forestry in the
Intermountain West
by Michael R. Kuhns
Abstract. This paper summarizes the people/population factors,
site factors, and program factors influencing urban and community forestry
(U&CF) in the Intermountain West, including information gathered through
a limited survey of U&CF experts in the region. The major factors that
emerged include a relatively low population living in cities and towns
scattered over a large area, major population growth now and in the future,
lack of native trees in the valleys where most people live, harsh conditions
for growing trees, poorly funded and staffed U&CF programs, and lack
of community and citizen awareness and knowledge, particularly regarding
tree selection and landscape design and care. An improving future is predicted
for U&CF in the region, based on population growth and demographic
change, increasing citizen interest and awareness, enhanced funding and
staffing of U&CF programs, and the availability of better-trained arborists.
Keywords. Urban forestry; community forestry; Intermountain West; population;
demographics; site; programs.
An Evaluation of the Residual
Activity of Traditional, Safe, and Biological Insecticides Against the
Gypsy Moth
by Ralph E. Webb, Randy Peiffer, Roger W. Fuester, Kevin W. Thorpe,
Louis Calabrese, and Joseph M. McLaughlin
Abstract. We evaluated the direct and the residual efficacy of
selected traditional, safer, and biological insecticides that are either
registered or are candidates for registration for use by arborists and
nurserymen in Integrated Pest Management (IPM) programs for gypsy moth
(Lymantria dispar) management in urban settings. The study compared 5 biological
insecticide treatments (1 Bacillus thuringiensis [Bt] and 4 gypsy moth
nuclear polyhedrosis virus [NPV] treatments) and 2 reduced-risk insecticides
(neem and tebufenozide) against 2 commonly used standard insecticides (diflubenzuron
and cyfluthrin). Significant details pertaining to the use of the specific
control materials were clarified in support of a decision matrix around
which an IPM system can be formulated for use by arborists and nurserymen.
The standard insecticides, cyfluthrin and diflubenzuron, and the ecdysone
agonist tebufenozide, demonstrated excellent activity against all instars
in both a 1-hour residue study and a 35-day residue study. Bt was clearly
more effective against second instar larvae than against fourth instar
larvae and lost significant activity against the gypsy moth after 7 days.
The efficacy of the neem product was similar to that of Bt in that it controlled
younger instars better than it did older instars. Although its speed of
action was slower than that of Bt, it remained highly active against gypsy
moth 21 days after treatment. NPV without the activity enhancer Blankophor
BBH gave significant levels of control for all 4 larval instars fed on
1-hour residues, although mortality was higher for younger instars than
for older instars. Residual effectiveness was significantly reduced after
1 day. The addition of Blankophor BBH to the NPV tank mix led to improved
kill in the 1-hour study and to vastly improved residual activity (up to
35 days).
Longevity of Ferric Ammonium
Citrate Treatments in Oak (Research Note)
by E. Thomas Smiley and Larry G. King
Abstract. Iron deficiency is a factor that limits the longevity of oaks grown in alkaline soils. Xylem injections of ferric ammonium citrate and urea were applied at a high rate in the fall to reduce symptom expression. Treatments significantly improved tree health for four years in both red and white oaks.