Irene Pines and Richard Westwood A Mark-recapture Technique for the Dutch Elm Disease Vector the Native Elm Bark Beetle, Hylurgopinus rufipes (Coleoptera: Scolytidae) ........................................................................................................116 Abstract. Six mark-recapture experiments were conducted in Manitoba, Canada, to determine the effectiveness of fluorescent powder to mark emerg- ing native elm bark beetle adults, Hylurgopinus rufipes (Eichoff) (Coleoptera: Scolytidae), the vector of Dutch elm disease, Ophiostoma novo-ulmi (Bra- zier), aſter departure from overwintering sites in spring and emergence from broodwood in summer. Native elm bark beetles marked themselves on emergence from overwintering sites and summer trap logs. The spring and summer periods of flight activity for unmarked and marked beetles were similar. Marked beetles were captured over 1 month aſter peak emergence in the spring and 2 months aſter emergence from trap logs in the summer. Marked beetles were captured up to 1 km (0.6 mi) from release sites. Where integrated Dutch elm disease management activities are implemented in buffer zones to minimize the number of elm bark beetles entering community urban forests, buffer zones should be a minimum of 1 km (0.6 mi) in width. Key Words. Dutch Elm Disease; Hylurgopinus rufipes; IPM; Marking; Plant Health Care; Scolytidae. E. Thomas Smiley Root Pruning and Stability of Young Willow Oak .................................................................................................... 123 Abstract. Two root-pruning methods simulated construction-related trenching and individual root cuts such as from decay aſter root prun- ing. Tree trunks were pulled to an angle of 1° from vertical using measured force. A third of the study trees were pulled to failure to deter- mine the relationship between the 1° pull force and the pull-to-failure force. The regression had correlation with r2 equal to 0.76. Util- ity trenching was simulated with linear cuts across the root zone. Measurable decreases in force applied occurred when cuts were within three times the trunk diameter from the trunk. Force decreased by 35% when a tangential cut was made at the trunk. When indi- vidual roots were severed, the pull force was reduced with each root cut. When one root was severed, the decrease in force averaged 12%; when half of the exposed buttress roots were severed, the decrease was 30%. Arborists should avoid cutting any tree roots near the trunk. Linear trenching should not be closer to the trunk than a distance equal to or greater than three times the trunk diameter. Key Words. Construction Damage; Pull Testing; Root Anchorage; Root Barrier; Root Decay; Root Plate; Utility Trenching; Windthrow. Henry D. Gerhold Serviceberry Cultivars Tested as Street Trees: Second Report ............................................................................... 129 Abstract. Through the Municipal Tree Restoration Program, cooperators planted eight serviceberry (Amelanchier spp.) cultivars in 15 com- munities for evaluation as street trees, typically comparing two in each community. Standardized measurements in years 1, 2, 3, 6, 9, and 12 revealed differences in trunk diameter, height, crown width, and health of foliage and branches. Among the four cultivars that have been tested most extensively, the main difference is that Cumulus® and Robin Hill are much taller in the twelſth year than Tradition® and Autumn Brilliance®. 'Cole's Select', 'Princess Dianna", ReflectionTM , and Spring Glory® also have been performing well for 6 to 10 years, but they have been tested at just one or two locations. Survival, growth, and health have been superior on more spacious sites, but with proper care, ser- viceberry cultivars can do well even along downtown streets. All eight of these cultivars are appropriate for planting under overhead wires. Key Words. Amelanchier; Performance Testing; Serviceberry Cultivars; Street Tree Evaluation. ©2008 | International Society of Arboriculture | ISSN:1935-5297
March 2008
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