Table of Contents Kahoru Matsumoto, Futoshi Ishiguri, Kazuya Iizuka, Shinso Yokota, Naoto Habu, and Nobuo Yoshizawa Evaluation of Compressive Strength of Decayed Wood in Magnolia obovata ................................ 81 Abstract. To obtain the basic information needed to estimate the degree of decay from compressive strength measured using a Fractometer (CS), relationships between CS and the contents of chemical components were analyzed for Magnolia wood decayed by three types fungi (brown rot, white rot, and soft rot fungi) at various decay levels. Weight loss ratio was sig- nificantly, negatively correlated with CS in woods decayed by brown rot and white rot fungi. In addition, a relatively high cor- relation coefficient was recognized between CS and holocellulose or α-cellulose content, except for wood decayed by soft rot fungus. The results obtained showed that Fractometer can detect the decrease of CS at relatively early stage of decay. Key Words. Compressive Strength; Core Sample; Decay Degree; Fractometer; Wood Decay. Glynn C. Percival and Kelly Noviss Evaluation of Potassium Phosphite and Myclobutanil Combinations for Pear Scab (Venturia pirina) Suppression ......................................................................................................... 86 Abstract. The purpose of this study was to investigate the use of potassium phosphite (Pi) alone and in combination with a reduced dose of synthetic fungicide (myclobutanil) to control pear scab (Venturia pirina) under field conditions. Irrespective of Pi and myclobutanil con- centration, no leaf or fruit phytotoxic effects were observed throughout the 2006 and 2007 experiments. In both field experiments, Pi alone significantly reduced the incidence and severity of V. pirina on leaves and fruit compared to water-treated control with the degree of scab reduction similar to that of a reduced dose of myclobutanil. The efficacy of Pi at 20 ml per liter water in inhibiting V. pirina scab incidence and severity was superior than that of Pi at 10 ml per liter water and a reduced dose of myclobutanil in virtually all monthly assessments. Combining a reduced dose of myclobutanil with either Pi at 10 ml or 20 ml per liter significantly improved the efficacy of scab control com- pared to stand alone applications of each product at most monthly assessments. Data analyzed with Limpel’s formula indicated a positive synergistic effect between Pi and a reduced dose of myclobutanil. Greatest reductions in V. pirina incidence and severity on leaves and fruit were, however, achieved by stand alone applications of myclobutanil at manufacturers recommended strength. Irrespective of year, crown volume, number of fruit per tree, and total fruit yield were higher in Pi and myclobutanil treated trees irrespective of concentration applied compared to water-treated controls. A combined mix of Pi with a reduced dose of myclobutanil proved effective in increasing crown vol- ume, number of fruit per tree and fruit yield compared to stand alone applications of each treatment. Greatest increases in crown volume, number of fruit per tree and fruit yield were achieved by applications of myclobutanil at the manufacturers recommended strength. In virtually all cases, Pi combined with a reduced dose of myclobutanil induced positive synergistic effects on crown volume and fruit yield greater than their additive effects alone. Mean fruit weight per tree were in all cases higher in Pi and myclobutanil treated trees irrespec- tive of concentration applied compared to water-treated controls, however, these differences were not statistically significant in all cases. Key Words. Fungicides, Integrated Disease Management; Orchard Management; Pathogen Control; Plant Health Care; Synergism; Urban Landscapes. Belinda B. Lambert, Steven J. Harper, and Stephen D. Robinson Effect of Container Size at Time of Planting on Tree Growth Rates for Baldcypress [Taxodium distichum (L.) Rich], Red Maple (Acer rubrum L.), and Longleaf Pine (Pinus palustris Mill.) ...................................................................................................................... 93 Abstract. The ecosystem restoration and wetland mitigation industries are challenged with recreating vegetative communities at an accelerated rate, while at the same time remaining cost effective. These created systems are typically bound by permit conditions to meet certain tree growth criteria in a specified time frame, commonly five years. Stock sizes of container grown trees are generally #1, #3, or #7 (gallons). The purpose of this study was to determine the relative cost effectiveness of these planting sizes for three com- monly used species and to assess whether they achieve common success criteria for height, percent survival, and percent cover. These three species are baldcypress [Taxodium distichum (L.) Rich], red maple (Acer rubrum L.), and longleaf pine (Pinus palustris Mill.). Based on the standard planting density of 174 trees/hectare, the most cost-effective size was #3 in all cases. All three sizes of baldcypress and red maple met the 3.7 m height criterion; no size of longleaf pine met the criterion. All sizes of all species failed to meet both the 85% survival standard and a theoretical minimum 50% cover calculated from canopy diameter mea- surements. If planting densities are increased to meet cover requirements and to offset mortality, container size #1 may be more favorable for baldcypress and red maple, but not for longleaf pine. The study was conducted in Pinellas County, Florida, U.S. Key Words. Habitat Restoration; Permit Requirements; Success Criteria; Tree Growth; Wetland Mitigation. ©2010 | International Society of Arboriculture | ISSN:1935-5297
March 2010
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