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.
Root Barrier and Extension Casing
Effects on Chinese Hackberry
by Paula J. Peper and Sylvia Mori
Abstract. In California, repairing sidewalk damage associated
with tree roots exceeds $62 million annually. Efforts to reduce sidewalk
damage have provided street tree managers with a variety of root barrier
products. In this study, 3 types of root barriers were installed and evaluated
to determine whether 1) internal vertical ribs prevented circling roots
and 2) root development would be significantly reduced in the top 30 cm
(12 in.) of soil. The 3 barriers tested included 1) a modified production
container, partially left in place when planted (extension casing), 2)
a commercial product with vertical ribs spaced 15 cm (6 in.) apart, intended
to prevent circling roots, and 3) a commercial product with vertical ribs
spaced 12.5 cm (5 in.) apart. Root diameter, depth, and dry weight were
measured for Chinese hackberry (Celtis sinensis) planted and grown for
3 years with and without root barriers. The extension casing reduced root
biomass in the top 33 cm (13 in.) of soil by 50% compared to trees without
barriers (controls). Mean root diameter of the 6 largest roots outside
of the casing was also significantly smaller. Mean root diameters and biomass
of controls were similar to those for the 2 commercial barriers. Roots
on the trees with root barriers escaped beyond the barrier walls then grew
upwards to depths similar to the controls (37 cm [14.5 in.]). Although
casings reduced total root biomass and diameter, they appeared to encourage
circling root growth. Circling was diminished when commercial barriers
with internal vertical ribs were used. Mean top growth was similar among
treatments.
Industrial-Area Street Trees in
Portland, Oregon
by Joseph Poracsky and Mark Scott
Abstract. Industrial-area trees have, with few exceptions, been
neglected by the research community as well as by urban forestry management
programs. A recent project in Portland, Oregon, provides both some data
and a program model that easily could be replicated in other communities.
An inventory of the Northwest Industrial Neighborhood Association (NINA)
district identified 966 street trees and 1,140 unplanted/potential street
tree sites, for a stocking level of 46%. While this figure is low relative
to most other segments of the urban forest, it was received optimistically
because it was higher than had been expected for an industrial area and
it demonstrated a great deal of potential for expanding the urban forest
through additional plantings. Diversity data indicated only 17 genera were
represented, identified two genera (Acer and Prunus) that were overplanted,
and provided guidance on which genera could be added to increase diversity.
NINA officials have formed a partnership with other local urban forestry
interests and are using the data to undertake a 10-year planting program
for the district.
Assessment of Fracture Moment
and Fracture Angle in 25 Tree Species in the United States Using the Fractometer
by Nelda P. Matheny, James R. Clark, Donna Attewell, Kevin Hillery,
A. William Graham, and Gerald Posner
Abstract. The fracture moment and fracture angle of core samples
from the lower trunk of 25 tree species were evaluated using the Fractometer,
a device developed at the Nuclear Research Institute, Karlsruhe, Germany.
In 6 additional species, core segments broke upon initial loading in the
Fractometer and values could not be obtained. Fracture moments and angles
were recorded for trees located in California, Oregon, Pennsylvania, and
Illinois. Results varied by species, core segment, and location of tree.
Application of the Fractometer to tree hazard evaluation procedures is
discussed.
The Appropriate Response Process
(ARP) and Its Role in Plant Health Care
by John Ball, John E. Lloyd, and Daniel F. Marion
Abstract. Plant health care (PHC) is presented as a strategy
for the professional care of ornamental landscapes. Plant health care incorporates
plant care practices, including integrated pest management (IPM), into
a comprehensive management system. This system requires that the practitioner
use information about the plant, the stressor, and the client when making
management decisions. The appropriate response process (ARP) is introduced
as a conceptual model of the PHC decision-making process.
Flood-Tolerance Ranking of Red and
Freeman Maple Cultivars
by Louis B. Anella and Thomas H. Whitlow
Abstract. Red maple (Acer rubrum) is often recommended for use
in wet soils, yet its extensive native range suggests there may be genetic
variation for traits associated with flood tolerance. Likewise, genetic
variation for flood tolerance may be captured within red maple cultivars
making some more appropriate than others for use in wet or low oxygen soils.
Seven red maple cultivars (2-year-old trees)-'Autumn Flame'®, 'Bowhall',
'Karpick', 'Northwood', 'October Glory'®, Red Sunset®, and 'Schlesinger-
and 4 Freeman maple (A. freemanii) cultivars-'Armstrong', 'Autumn Blaze',
'Morgan', and Scarlet Sentinel™, were ranked for flood tolerance by flooding
the trees and characterizing photosynthesis, lenticel intumescence, and
survival. Indicator trees representing the wet extreme of red maple's native
range were also included for comparison. Net photosynthesis declined for
all cultivars; however, 'Schlesinger', Red Sunset and 'Bowhall' had the
highest net photosynthetic rates (ranging from 1.94 to 1.71 µmol/m2s)
after 45 days of flooding. In contrast, 'Karpick', 'Autumn Flame', and
'Northwood' had net photosynthetic rates near 0. The extent of lenticel
intumescence also varied among the cultivars with 'Schlesinger' and 'Bowhall'
producing the longest lenticels. All of the 'Northwood' trees died, as
did two-thirds of the 'Autumn Flame' trees. The cultivars were separated
into 3 overall flood-tolerance rankings: high ('Schlesinger', Red Sunset,
and 'Bowhall'), intermediate ('Armstrong', 'Morgan', 'October Glory', Scarlet
Sentinel, and 'Autumn Blaze'), and low ('Karpick', 'Autumn Flame', and
'Northwood').
Use of Soil and Trunk Injection
of Systemic Insecticides to Control Lace Bug on Hawthorn
by Stanton Gill, David K. Jefferson, Rondalyn M. Reeser, and Michael
J. Raupp
Abstract. Several systemic insecticides are labeled for control
of sucking insect pests of trees, and numerous application methods are
available for arborists. A field trial was conducted to test 2 formulations
of imidacloprid (Pointer 4% and Merit 75 WP systemic insecticides), a formulation
of abamectin (Greyhound 1.9%, B1), and 2 different delivery systems. The
delivery systems evaluated were the Kioritz soil injector and ArborSystem's
Wedgle-tip tree injection system. The target pest in this field trial was
hawthorn lace bug (Corythucha cydoniae) on hawthorn (Crataegus viridis)
trees. The Kioritz is a handheld soil injector made for injecting fertilizer
and systemic pesticides into the root zone of trees and shrubs with relatively
small amounts of water. The Wedgle tip is an injection system that uses
a blunt-edged tip inserted through a small hole through the bark, just
to the edge of the sapwood. Wounding to the tree with the Wedgle tip is
minimal. This study indicates that systemic insecticides applied through
soil injection and trunk injection have potential for controlling sucking
insects that feed on ornamental trees.
Tree Growth Regulator Effect
on Phototropism-Its Implication for Utility Forestry
by Chad E. Sperry and William R. Chaney
Abstract. Pruning procedures such as V-trimming or side-trimming used by electric utilities in tree maintenance programs result in asymmetrical light exposure within tree canopies, producing the potential for phototropic growth response. The tree growth regulators (TGRs) paclobutrazol and flurprimidol are used to reduce the rate of shoot regrowth following pruning. The mode of action involves complexing of the growth retardant with cytochrome P450-dependent enzymes in the metabolic pathway for gibberellins, plant hormones responsible for shoot elongation. Because cytochrome P450 also is a part of the blue light receptor system that controls phototropism, it was hypothesized that shoot growth, as well as phototropic curvature, would be reduced by paclobutrazol and flurprimidol. Effects of soil-applied (0, 0.5, 1, and 5 ppm) paclobutrazol and flurprimidol on shoot growth and phototropism of greenhouse-grown seedlings were found to vary among species. Neither shoot growth nor phototropic curvature in American sycamore (Platanus occidentalis L.) was reduced by treatment with the TGRs. In contrast, shoot growth of silver maple (Acer saccharinum L.) was reduced by all concentrations of both paclobutrazol and flurprimidol, whereas phototropic curvature was reduced only by flurprimidol. Phototropic curvature of etiolated zinnia (Zinnia elegans 'Scarlet' Jacq.) was reduced by both growth regulators.
Patterns of Structural Failures
in Urban Trees: Coast Live Oak (Quercus agrifolia)
by Roger Edberg and Alison Berry
Abstract. Data from the California Tree Failure Report Program
(CTFRP) were analyzed to develop a profile of the structural failure characteristics
for coast live oak (Quercus agrifolia). The most common pattern of structural
failure for coast live oak reported in the CTFRP is a root or low trunk
failure of a naturally occurring tree growing in a residential site. Decay,
site grade changes, and low wind speeds are significantly more frequently
associated with coast live oak failures than with other hardwoods, conifers,
or eucalyptus. Decay of roots and lower trunk was a major contributing
factor to failure of coast live oak (83%). Saturated soil conditions associated
with root failure were also more frequent for coast live oak than for other
species groups. Careful attention to controlling excess soil moisture,
avoiding or correcting grade change and compaction, and monitoring decay
are essential to maintain the health of coast live oak.