Table of Contents Edward F. Gilman, Jason Miesbauer, Chris Harchick, and Richard C. Beeson Impact of Tree Size and Container Volume at Planting, Mulch, and Irrigation on Acer rubrum L. Growth and Anchorage ................................................................................................................. 173 Abstract. Some trees uproot in storms apparently due to root deflections that occur during nursery production. Root deflection in a nursery container may lead to poor anchorage because of insufficient root growth into the landscape soil, and container volume/tree size at planting may influence root deflection. This study was designed to evaluate establishment, root growth, and anchorage six years aſter planting Acer rubrum L. trees of four different sizes from four corresponding container volumes and maintaining them with two irrigation regimes. Impact of mulch on establishment and root growth was also evaluated. Trees from the largest containers grew slowest in the first three years due primarily to water stress. Trunk tilt during winching tests increased due to greater root deflection, less mass of the root-soil plate, and reduced root growth into the landscape soil with increasing container volume and tree size. In contrast to the poorly anchored larger trees that had most of their large roots retained in the original planted root ball volume, the largest roots on trees from smaller containers grew freely into landscape soil. This resulted in stable trees with many stiff, straight roots pushing down against mineral landscape soil outside the root ball during winch- ing. Trees planted from smaller containers appear to anchor sooner than trees from larger containers and would be more stable in a storm. Key Words. Bending Stress; Container Production; Root-soil Plate; Straight Roots. Glynn C. Percival and Jonathan M. Banks Water-retaining Polymer and Fungicide Combinations Reduce Disease Severity Caused by Horsechestnut Leaf Blotch [Guignardia aesculi (Peck) VB Stewart] ............................................. 182 Abstract. The influence of six commercially available fungicides incorporated into a water-retaining polymer and applied to the root sys- tem of horsechestnut (Aesculus hippocastanum L.) as a dip at the time of planting was conducted. Potential increases in resistance against the foliar pathogen Guignardia leaf blotch (Guignardia aesculi) was then monitored over two growing seasons. Trials were conducted in 2007 and duplicated in 2008. A comparative evaluation of the fungicide penconazole commercially used for Guignardia leaf blotch control was studied by spraying trees at the manufacturer’s recommended rate of four times during the first growing season but none in the second. None of the treated or control trees died as a result of Guignardia leaf blotch attack during the course of the study and none of the fungicide and water-retaining polymer combinations evaluated was phytotoxic to the test trees. Efficacy as Guignardia leaf blotch protectant com- pounds over the first growing season was demonstrated when fungicides were incorporated into a water-retaining polymer. Reductions in Guignardia leaf blotch severity were mirrored by increases in leaf chlorophyll fluorescence as a measure of leaf photosynthetic activity and leaf chlorophyll content SPAD values. There were little differences in the magnitude of control efficacy between the fungicides evaluated. Limited efficacy of any of the fungicide and water-retaining polymer combinations as Guignardia leaf blotch protectant compounds was, however, demonstrated the following year after application indicating a fungicide and water-retaining polymer root dip provided one grow- ing season protection only. Application of a water-retaining polymer alone had no effect on reducing Guignardia leaf blotch severity. Based on visual Guignardia leaf blotch severity ratings, greatest protection in both the 2007 and 2008 trial was provided by the synthetic fungicide penconazole applied as a foliar spray four times during the growing season. No efficacy of penconazole foliar sprays as leaf blotch pro- tectant compounds was demonstrated the following year, indicating annual sprays against Guignardia leaf blotch are required for control. Key Words. Aesculus hippocastanum; Disease Management; Chlorophyll Fluorescence; Leaf Chlorophyll Content; Plant Health Care; Tree Planting. Emily Jack-Scott, Max Piana, Blake Troxel, Colleen Murphy-Dunning, and Mark S. Ashton Stewardship Success: How Community Group Dynamics Affect Urban Street Tree Survival and Growth ................................................................................................................................... 189 Abstract. Over the last two decades, there has been a substantial increase in street tree plantings across the United States. Many cities have set ambitious planting goals, relying on volunteer community groups to meet them. Existing research demonstrates that community steward- ship increases the survival of urban street trees. There is a lack of research, however, on how defining characteristics of community groups affect the survival and growth of the trees they plant. This study explores the significance of community group size (# participants), type (apartment, block watch, church, concerned neighbors, park, public housing, school, and social service), planting longevity (# years active), experience level (# trees planted), and neighborhood (geo-political boundaries). Measured for this study were 1393 trees planted from 1995 to 2007, by 134 groups, through the Urban Resources Initiative’s Community Greenspace program in New Haven, Connecticut, U.S. There was an overall survival rate of 76%. Highest survival and growth was found among trees planted by groups with more planting expe- rience, greater longevity, and more participants. Higher tree survival and growth was observed when trees were planted by groups work- ing in line with their mission (e.g., park groups in parks). Lowest survival and growth was found among yard trees planted by public housing groups. Existing canopy cover and neighborhood percent homeownership had little effect on survival or growth. This research can offer guid- ance for city managers by suggesting which planting groups require particular assistance in conducting successful, lasting street tree plantings. Key Words. Community Forestry; Connecticut; Mean Annual Growth Increment; Mortality; Percent Live Crown; Planting; Stewardship; Urban Ecology; Urban Forestry; Volunteer. ©2013 | International Society of Arboriculture | ISSN:1935-5297
July 2013
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