Published by the International Society of Arboriculture.
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.
Patrick L. Burch, Richard H. Wells, and William N. Kline, III
Abstract. Trees treated with soil-injected paclobutrazol tree growth regulator (TGR) were compared to untreated trees 10 years after treatment. Red maple and silver maple were treated in 1984, 2 months after being trimmed, with 0.5, 1.0, or 2.0 g of active ingredient (gai) per inch diameter at breast height (dbh). The volume of delivery varied for silver maple (300, 1500, or 3000 mL per tree); however, red maple were all treated at 1500 mL per tree. The untreated trees required trimming again in 1988 and 1990. No information was collected at these trimming dates. All trees, treated and untreated, were then trimmed in 1994; the biomass removed and the time taken to trim and chip the trees were recorded for each tree. Treated trees had significantly less biomass removed than did untreated trees. Considering that the untreated trees had been trimmed an additional two times, further separation between the treated and untreated trees was evident. Reductions in biomass correlate well with reductions in time required to trim the trees and chip the biomass removed. Differences among application volumes demonstrated the importance of proper TGR placement for best results. At higher application volumes, there were no significant differences between the 1- and 2-g rates.
Jane Leslie Hayes, James R. Meeker, John L. Foltz, and Brian L. Strom
Abstract. Southern pine beetles (SPB), and associated bark beetles, have long been recognized as major pests of southern forests. Tactics used for controlling infestations in conventional forest settings have not proven effective at achieving area-wide control, nor are they suitable for the control of infestations in high-value stands such as homesites or wildlife habitat areas. Limited options exist for protecting high-risk uninfested pines of urban forests and often pose undesirable risks. One of the most promising areas in bark beetle research currently being experimentally tested on a large-scale is the use of deterrent behavioral chemicals (semiochemicals), produced by the insects or their host trees, as biopesticides to disrupt or inhibit infestations. In addition to traditional suppression tactics instituted in an unprecedented SPB outbreak in Gainesville, Florida, a semiochemical, 4-allylanisole (4-AA), was successfully tested as a protectant of pines in residential areas. 4-AA is a host-produced compound with repellent properties to many species of conifer-feeding bark beetles. The "freak" SPB outbreak in this urban environment and successful actions taken to mitigate damage are discussed.
David V. Bloniarz and H. Dennis P. Ryan, III
Abstract. The accuracy and validity of urban forest resource data collected by trained volunteers were established, using an actual case study in Brookline, Massachusetts. Results indicate that the data collected by trained volunteers are valid, and the accuracy compares favorably with levels found among a control group of certified arborists. Indirect benefits associated with this type of volunteer effort include the development of a more informed urban forest constituency, increased environmental awareness, an increased political voice, and an improved quality of life for urban residents. The cost of utilizing community volunteers to conduct urban forest inventories is competitive with similar programs conducted by professional arborists.
Daniel A. Brown, Mark T. Windham, and Robert N. Trigiano
Abstract. Dogwood anthracnose caused by Discula destructiva poses a threat to flowering (Cornus florida) and Chinese (C. kousa) dogwood in the eastern United States and to Pacific or western dogwood (C. nutallii) in the Pacific Northwest. Differences exist in the impact the pathogen has on these hosts (subjectively in the order C. florida > C. kousa and C. nutallii). Ten Cornus species, including C. alternifolia, C. amomum, C. controversa, C. alba, C. augustata, C. florida, C. kousa, C. mas, C. sericea, and C. stolonifera, were evaluated for disease reaction in 1991 and 1992 at locations in eastern Tennessee infested with D. destructiva. Greatest disease severity in 1991 was observed on C. controversa, C. florida, C. kousa cv 'Chinensis', and C. sericea. In 1992, C. florida, C. sericea, C. kousa cv 'Chinensis', C. alba, and C. stolonifera cultivars appeared susceptible to anthracnose. Symptoms developing on each appeared similar to those observed on flowering dogwood, and D. destructiva was successfully isolated from lesions within the canopy of the trees. Other Cornus species tested, including an unnamed Chinese dogwood cultivar, appeared resistant. The results of this study indicate that concerns regarding the anthracnose susceptibility of native and ornamental Cornus species may be raised. Finally, the possibility should be considered that infected Cornus species (other than C. florida) might serve as a mechanism for the introduction of D. destructiva into anthracnose-free areas of the United States.
Kevin W. Thorpe
Abstract. The combined effect of insecticide applications using hydraulic equipment and sticky trunk barriers was tested on individual white oak (Quercus alba) trees under heavy gypsy moth (Lymantria dispar) pressure. The insecticides tested were insecticidal soap, Bacillus thuringiensis (B.t.), and cyfluthrin. One week after treatment, the B.t. and cyfluthrin treatments reduced larval density from 500 larvae per m2 of ground surface beneath the canopy on unsprayed, unbanded trees to 180 and 30 larvae per m2, respectively. Defoliation exceeded 75% on unsprayed, unbanded trees and unbanded trees sprayed with soap, but remained below 25% on trees sprayed with B.t. or cyfluthrin. Trunk barriers reduced larval density and defoliation under all insecticide treatments and on unsprayed trees, but their effect was minimal on trees treated with B.t. or cyfluthrin. None of the treatments affected the total number of gypsy moth egg masses on treated trees. These results indicate that ground-based applications of both B.t. and cyfluthrin can provide good foliage protection, but that the use of trunk barriers with these treatments provides little or no added benefit. The soap, which is a contact insecticide, did not provide adequate foliage protection.
Steven Vogel
Abstract. Many of the features of trees represent arrangements that minimize the chance that they will uproot when exposed to high winds. At least four schemes, singly or in combination, keep the bases of trees from rotating in the face of the turning moment imposed by the drag of their leaves. Trunks and petioles are relatively more resistant to bending than to twisting, giving good support but permitting drag-reducing reconfiguration in high winds. Leaves curl and cluster in a variety of ways, all of which greatly reduce the drag they incur relative to the values for ordinary thin and flexible objects such as flags. However, information derived from measurement and experimentation about such mechanical matters is still quite limited.
W.C Bramble, W.R. Byrnes, R.J. Hutnik, and S.J. Liscinsky
Abstract. An investigation of factors responsible for resistance of forb-grass cover types to tree invasion was carried out from 1992 through 1994 on an electric transmission right-of-way (ROW) in central Pennsylvania. Unprotected seedspots and seedspots protected by wire cages were installed on the ROW to investigate the effect of the important interference factors of wildlife depredation, plant competition, and allelopathy. This field study was supplemented by pot culture tests of the effect of plant competition, seedbed condition, and allelopathy on tree seed germination and seedling growth in an environment where wildlife depredation, soil moisture, frost damage, and insect and disease attacks were controlled. The major factors that interfered with tree seed germination and seedling growth were wildlife depredation and plant competition by the dominant plant species of the forb-grass cover type, namely, poverty grass (Danthonia spicata), rough goldenrod (Solidago rugosa), and hayscented fern (Dennstaedtia punctilobula).