ARBORICULTURE & CONTENTS Abstract. Paclobutrazol (PBZ)(0 g L-1 URBAN FORESTRY Volume 47, No. 2, March 2021 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) Ahmad Nazarudin Mohd Roseli, Tsan Fui Ying, and Normaniza Osman Changes in Leaf Thickness, Chlorophyll Content, and Gas Exchange of a Landscape Tree, , 0.125 g L-1 ) and potassium nitrate (KNO3)(0 g tree-1 , 100 g tree-1 , Treated with Paclobutrazol and Potassium Nitrate ........53 , and 0.25 g L-1 , and 200 g tree-1 ) were have been previously reported; in addition to these, the influences on leaf thickness and leaf physiology, including chloro- phyll content and gas exchange, are discussed in this study. Relative chlorophyll content was significantly increased with PBZ and/or KNO3 enhancing leaf greenness. Increased leaf thickness of up to 13.37% at 6 months after treatment with a combination of PBZ and KNO3 , was observed. The presence of PBZ significantly reduced the photosynthetic and transpiration rates and stomatal conductance. Reduced leaf phys- iological traits combined with thicker leaves would be beneficial for trees to tolerate harsh urban settings. Therefore, a combination of PBZ and KNO3 is recommended for stress tolerance enhancement of X. chrysanthus grown as a landscape tree. Keywords. Golden Penda; Leaf Physiology; Photosynthesis; Plant Growth Regulator; Urban Tree. Kevin D. Chase, Elden LeBrun, and Chad M. Rigsby Efficacy of Flupyradifurone, Pyriproxyfen and Horticultural Oil, and Dinotefuran Against Gloomy Scale ( tested on a landscape tree, Xanthostemon chrysanthus (F. Muell.) Benth., in an attempt to enhance its stress tolerance under harsh urban condi- tions. Significant effects on tree height, diameter at breast height, canopy diameter, leaf area, and anatomy of tree leaves and stems in response to PBZ and KNO3 Comstock) ....................................................64 Abstract. Gloomy scale (GS)(Melanaspis tenebricosa) is a major pest of red maple (Acer rubrum) across much of the eastern USA. Current pesticide recommendations for GS management are efficacious when applications are made at the appropriate time. However, appropriate tim- ing may not always be possible. For instance, the tree owner may not contact pest management professionals in time to make timely applica- tions. We established a field trial to determine the efficacy of the pesticides pyriproxyfen plus horticultural oil and dinotefuran, as well as a relatively new pesticide available in the ornamental woody plant market, flupyradifurone, against GS. There were three primary goals of this study: (1) to quantitatively compare the effectiveness of pyriproxyfen plus horticultural oil and dinotefuran; (2) to compare flupyradifurone with these two generally recommended treatments; and (3) to assess whether flupyradifurone is effective when applications are made later in the summer. We found that pyriproxyfen plus horticultural oil, dinotefuran, and flupyradifurone applications made during the active crawler period were equally efficacious, statistically, and that flupyradifurone treatments applied later in the summer were not statistically differentia- ble from untreated controls. While these pesticide applications are effective at suppressing GS populations, plant health care tactics aimed at preventing outbreaks should be prioritized and incorporated into the complete pest management strategy. Keywords. Armored Scale; Pesticide Trial; Urban Trees. Lai Fern Genevieve Ow and Dloysius Chow Urban Stormwater Management: Can Tree Roots and Structural Soils Improve Hydraulic Conductivity into Compacted Soils? .........................................................................72 Abstract. Typically, surface precipitation runoff is a key source of flooding and water pollution in urban communities, and the costly and time-consuming process of installing bio-retention basins is one approach to overcoming these challenges. The implementation of structural soils in bio-retention basins designed to receive and retain stormwater provides these systems with additional functions to bear loads and facil- itate tree root growth and exploration. The channels that tree roots produce as they grow can also aid in the flow of water down the soil profile. In this study, the potential for tree roots to penetrate compacted soils and increase rates of hydraulic conductivity were examined alongside the use of structural soil in the context of urban stormwater systems. For the first experiment, Pouteria obovata and Calophyllum soulattri together with a control (without tree) were placed in cylindrical planting sleeves surrounded by compacted clay loam at two compaction levels (bulk ©2021 International Society of Arboriculture Xanthostemon c hr ysanthus Melanaspis tene bricosa
March 2021
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