Table of Contents Rodrigo A. Chorbadjian, Pierluigi Bonello, and Daniel A. Herms Effect of the Growth Regulator Paclobutrazol and Fertilization on Defensive Chemistry and Herbivore Resistance of Austrian Pine (Pinus nigra) and Paper Birch (Betula papyrifera) ........... 278 Abstract. The Growth/Differentiation Balance Hypothesis predicts that environmental factors that limit growth of plants more than their rate of photosynthesis should increase secondary metabolism and resistance to insects. Soil drench application of the plant growth regulator paclobutra- zol slowed the growth of paper birch (Betula papyrifera) and Austrian pine (Pinus nigra) with no effect on photosynthesis. In response, foliar concentrations of condensed tannins (but not total phenolics) in birch increased as predicted, which increased birch resistance to gypsy moth (Lymantria dispar) and whitemarked tussock moth (Orgyia leucostigma), but only during the second season aſter treatment. In both years, there was a negative correlation between foliar concentrations of total phenolic and condensed tannins and growth of paper birch, which is consistent with the predicted trade-off between growth and defense. Conversely, in Austrian pine, paclobutrazol and fertilization did not have an effect on foliar concentration of tannins, phenolics, and terpenes, nor did the treatments have any effect on resistance to European pine sawfly (Neodiprion sertifer). Hence, the effects of paclobutrazol on tree growth, defensive chemistry, and insect resistance were species-specific and time sensitive. Key Words. Allocation Trade-offs; Growth/Differentiation Balance Hypothesis; Growth Regulator; Insect Resistance; Plant Defense Theory. Joseph J. Doccola, Brian L. Strom, Cavell Brownie, and Kier D. Klepzig Impact of Systemic Fungicides on Lesions Formed by Inoculation with the Bluestain Fungus (Ophiostoma minus) in Loblolly Pine (Pinus taeda L.) ...................................................... 288 Abstract. Ophiostomatoid fungi are important components within the highly damaging insect-fungal complexes attacking trees in North America. This group includes the disease agents responsible for Dutch elm disease and laurel wilt, as well as a number of associ- ates of tree-killing bark beetles. While systemic fungicides have been applied against ophiostomatoids in certain fungus-host systems, the breadth of their utility and their management implications for a wide array of fungus and host species remain uncertain. To evalu- ate the impact of commercially available fungicides against the bluestaining fungus Ophiostoma minus, an associate of the southern pine beetle, researchers conducted two experiments with loblolly pines (Pinus taeda; mean dbh 14.2 and 18.5 cm, respectively) in central Loui- siana, U.S. The first experiment screened three fungicides (Alamo®, Arbotect® 20-S, and PHOSPHO-jet) for their systemic impacts on O. minus, and the second further evaluated the best performing product (Alamo) alone and in combination with Arbotect 20-S. In all cases, loblolly pines were stem-injected basally and challenged with inoculations of cultured O. minus at time periods ranging from 28 days to 738 days post-treatment. In both experiments, treatment of loblolly pines with Alamo produced the smallest lesion areas, indi- cating that this treatment was the most effective for limiting the within-tree growth of O. minus. This effect was still present more than two years post-treatment. The study authors conclude that Alamo is the most effective product of those evaluated for prophylactic treat- ment against O. minus, and suggest that evidence is building for the effectiveness of this product generally against ophiostomatoid fungi. Key Words. Dendroctonus frontalis; Scolytidae; Propiconazole; Southern Pine Beetle; Systemic Injection; Vascular Wilt. Kelby Fite, E. Thomas Smiley, John McIntyre, and Christina E. Wells Evaluation of a Soil Decompaction and Amendment Process for Urban Trees ............................ 293 Abstract. Researchers investigated the effects of a soil decompaction and amendment process (AFM) and its individual components (air tillage, fertilizer, and mulch) on soil properties at four urban sites: Anderson, South Carolina; Boston, Massachusetts; Myrtle Beach, South Carolina; and Pittsburgh, Pennsylvania, U.S. At each site, 50 red maples (Acer rubrum) were growing on compacted and/or nutrient-poor soils whose pre- treatment bulk densities ranged from 1.14 to 1.74 g/cm3 were taken through the end of 2008. The AFM treatment significantly reduced soil strength relative to control at all sites in 2006. There were significant treatment × location interactions in all years, with higher bulk density sites (Anderson and Myrtle Beach) showing the greatest magni- tude and duration of response. The AFM and mulch treatments generally increased soil organic matter content, while air tillage alone signifi- cantly lowered soil organic matter content in Pittsburgh. At most sites, the AFM treatment was more effective than surface fertilizer application at improving soil fertility. AFM and mulched plots had significantly higher soil water content than other plots during periods of summer drought. Overall, AFM was effective in improving soils beneath established trees, and mulching was the most beneficial of the individual treatments. Key Words. Acer rubrum L.; Air Tillage; Decompaction; Fertilizer; Mulch; Organic Matter; Soil Strength; Urban Soils. . Treatments were applied in the autumn and winter of 2005–2006, and measurements ©2011 | International Society of Arboriculture | ISSN:1935-5297
November 2011
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