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COMPARISON OF HURRICANE DAMAGE
TO SEVERAL SPECIES OF URBAN TREES IN SAN JUAN, PUERTO RICO
by John K. Francis
Abstract. Percent defoliation and percent crown loss were estimated, and a count of stem failure was taken for 24 species of urban trees in San Juan following Hurricane Georges. Differences among species were significant, and detailed comparisons are presented. Wood-specific gravity, branch resistance to flexing, and leaf retention strength were measured for the study species. Many significant correlations were noted between pre-storm height, diameter, wood-specific gravity, branch resistance to flexing, leaf retention strength, defoliation, percent crown loss, and stem failure. A regression equation predicting defoliation is presented. Tree height was the most influential variable followed by branch resistance to flexing, leaf retention strength, and wood-specific gravity. If tree height was eliminated from the model, specific gravity then entered the stepwise regression first.
VEGETATION MANAGEMENT ALONG
TRANSMISSION UTILITY LINES IN THE UNITED STATES AND CANADA
by Joseph A. Sulak and J. James Kielbaso
Abstract. A survey investigating vegetation control methods along transmission rights-of-way was sent to 220 Utility Arborist Association companies. The survey contained questions regarding right-of-way characteristics, control methods used, total dollars spent on vegetation management, and priorities of the vegetation management program. The ROW area reported represented over 48% of all the investor-owned ROWs over 39 Kv in service throughout the United States. More than 75% of the respondents reported using herbicides on their rights-of-way. However, acres treated mechanically outnumbered those treated chemically by a margin of 2.7:1. Garlon 3A and Garlon 4 topped all herbicides, with a combined 220,574 projected gal (834,961 L) of the estimated 549,869 gal (2,081,474 L) of herbicide applied to transmission rights-of-way in 1995. It appears that quite low levels of active ingredients are being applied per acre. Basal, high-volume foliar, and low-volume foliar with a backpack or handgun applications accounted for approximately 75% of the acres of transmission ROWs treated with herbicides.
DETERMINATION OF PARENTAGE
OF FLOWERING DOGWOOD (CORNUS FLORIDA) SEEDLINGS USING DNA AMPLIFICATION
FINGERPRINTING
by Malissa H. Ament, Mark T. Windham, and Robert N. Trigiano
Abstract.Open-pollinated seedlings of Cornus florida L. 'Cherokee Chief' were tested to identify the pollen donor from a list of nearby C. florida trees using DNA amplification fingerprinting (DAF). Tissue was collected and DNA isolated from the maternal 'Cherokee Chief' tree and possible pollen donors C. florida 'Cherokee Brave', 'Cherokee Daybreak', 'Cloud 9', 'Springtime', and 'Pygmy'. DNA was also isolated from C. florida 'Fragrant Cloud', 'Cherokee Princess', and 'Appalachian Spring'. Data from DAF were analyzed for similarities and differences between genetic makeup of seedlings and putative parents. Thirteen of 15 (87%) evaluated seedlings were the progeny of 'Cherokee Brave' and 'Cherokee Chief'. Using open pollination, progeny of 2 red-bracted C. florida cultivars 'Cherokee Brave' and 'Cherokee Chief' were obtained and subsequently verified using DAF.
ROOT BARRIERS AND WINDTHROW POTENTIAL
by E. Thomas Smiley, Albert Key, and Craig Greco
Abstract. This study was developed to determine if commercially available ribbed barriers reduce or increase the stability of trees under severe lateral stress. Green ash (Fraxinus pennsylvanica) were planted in November 1996: 6 in surrounding-type tree root barriers and 6 without barriers. Half of each group was pulled over in July 1999 under dry (14% water) soil conditions and the other half was pulled over under saturated (33% water) soil conditions. The force required to pull the trees over was measured as was the wind resistance of the trees. Slightly more force was required to pull over the trees grown within root barriers than the control trees. The force required for the weakest tree, however, was far greater than that exerted by a 100-mph (160-kph) wind. The reason for the increased strength of the root barrier trees appeared to be the deeper root system.
CEDRUS--THE TRUE CEDARS
by Paula. M. Pijut
Abstract. The true cedars (genus Cedrus) are valuable timber trees and striking specimen plantings in the urban landscape that grow well in a variety of soil and climatic conditions. The wood is durable and decay resistant. Cedars have been successfully introduced into areas outside of their natural range. The 4 species of Cedrus, 3 of which are planted to some extent in the United States, are C. atlantica (Atlas cedar), C. brevifolia (Cyprian cedar), C. deodara (Deodar cedar), and C. libani (Cedar of Lebanon). In this review, the geographical distribution, taxonomic characteristics, propagation, and adaptation to the urban landscape of cedars are discussed. This information is relevant to horticulturists, botanists, foresters, and anyone interested in the field of arboriculture.
OBSERVATIONS ON THE BIOLOGY
AND CONTROL OF THE HAWTHORN (TWO-CIRCULI) MEALYBUG, PHENACOCCUS DEARNESSI
(KING)
Whitney Cranshaw, Zana Jevremovic, D. Casey Sclar, and Loretta Mannix
Abstract. The hawthorn (two-circuli) mealybug, Phenacoccus dearnessi
(King), is a serious woody plant pest of hawthorn (Crataegus spp.)
in Colorado. With the expanded use of this plant in landscape settings,
P.
dearnessi has become of more economic importance. Studies were conducted
to better understand its biology and to evaluate management strategies.
In the area of Fort Collins, Colorado, nymphs emerged from overwintering
sites on trunks and began spring activity on 20 March 1998. Migration to
twigs was first noted on 14 April, peaking in early May and ceasing at
the end of the month. Adult females first produced living young on 27 May
and continued to reproduce until 14 October. Three species of predaceous
lady beetles--Adalia bipunctata (L.), Coccinella septempunctata
(L.), and Hippodamia convergens (Guerin-Meneville)--were observed
feeding on P. dearnessi nymphs as they emerged from overwintering
sites, but predation of mature females was not observed; no parasitoids
have been observed. There is a range of susceptibility to this insect among
Crataegus
spp.: Crataegus phaenopyrum 'Cordata' has remained highly resistant
to infestation throughout this study; Crataegus mordenensis 'Snowbird',
C. succulenta macracantha, and C. ambigua also showed substantial
levels of resistance. A wide range of insecticides has been evaluated for
control, with imidacloprid (Merit) and permethrin (Astro) among the most
effective. In addition, the use of horticultural oil consistently improved
performance. However, timing of application seems to be critical; applications
coinciding with migration of the overwintered nymphs to the twigs being
particularly effective.