ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 35, Issue 1, January 2009 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) www.isa-arbor.com Benjamin K. Hoover, Ricky M. Bates, James C. Sellmer, and Gregory A. Hoover Challenging Chinese Hemlock (Tsuga chinensis) with Hemlock Woolly Adelgid (Adelges tsugae) Ovisacs .................................................................................................................. 1 Abstract. Chinese hemlock (Tsuga chinensis) is a promising candidate for use as an ornamental tree in the mid-Atlantic region of the United States where native hemlocks have been devastated by hemlock woolly adelgid (Adelges tsugae). Published research has indicated that Chinese hemlock is adaptable to USDA Zone 6 and has some degree of resistance to hemlock woolly adelgid. Chinese hemlock has been observed to be resistant to hemlock woolly adelgid while growing in close proximity to infested eastern hemlocks, although a direct challenge of the species has not previously been documented. This study reports on the develop- ment of a procedure for challenging hemlocks with hemlock woolly adelgid ovisacs to determine host plant resistance and the use of the procedure to challenge Chinese hemlock. Chinese hemlock demonstrated complete resistance to hemlock woolly adelgid. Key Words. Adelges tsugae; Hemlock; Hemlock woolly adelgid; Host resistance; Integrated Pest Management (IPM); Plant health techniques; Tsuga canadensis; Tsuga chinensis. Paul A. Weston and Richard W. Harper Potential of Tsuga spp. from Western North America and Asia as Replacements for Eastern Hemlock (Tsuga canadensis) ............................................................................................... 5 Abstract. Hemlock woolly adelgid (Adelges tsugae) has had a devastating impact on Tsuga canadensis and T. caroliniana in forests and managed landscapes in the eastern United States. Species of Tsuga from the western United States and Asia are reported to be tolerant or resistant to A. tsugae. We established plots containing T. canadensis, T. caroliniana, T. chinensis, T. diversifolia, T. heterophylla, T. mertensiana, and T. sieboldii in Katonah, New York, U.S., an area with high populations of A. tsugae, and mon- itored tree growth and infestation by adelgids over a 4-year period. Growth and survival of the hemlock species varied widely, the most vigorous species being T. canadensis and T. chinensis. Susceptibility to the adelgid also varied widely among spe- cies; some species (particularly T. canadensis) became readily infested, whereas others (e.g., T. chinensis) were apparently entirely resistant. Given the ability of T. chinensis to thrive in the climate of southeastern New York State and its apparent resis- tance to hemlock woolly adelgid, this species might be an appropriate replacement species, especially in managed landscapes. Key Words. Elongate hemlock scale; Hemlock; Hemlock woolly adelgid; Host resistance; Tsuga. Daniel K. Struve Tree Establishment: A Review of Some of the Factors Affecting Transplant Survival and Establishment .......................................................................................................................... 10 Abstract. Transplant success and tree establishment depend on a chain of events from propagation, to production, to harvest, to shipping, to maintenance on the job site, to transplanting techniques, to aftercare. Failure to follow proper prac- tices at any step in this sequence will compromise transplant success and establishment. This article reviews some of the factors that induce transplant shock and slow establishment of transplanted nursery stock such as root and min- eral nutrient loss, soil moisture stress and xylem vessel cavitation, and methods used to reduce transplant shock. Key Words. Biostimulants; Establishment; Root growth potential; Transplanting. ©2009 | International Society of Arboriculture | ISSN:1935-5297
January 2009
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