Thayne Montague, Cynthia McKenney, Michael Maurer, and Brian Winn Influence of Irrigation Volume and Mulch on Establishment of Select Shrub Species ....................................... 202 Abstract. In many climates, irrigating shrubs during establishment is critical for long-term growth and survival. However, little research has been conducted to investigate irrigation requirements of newly transplanted container-grown shrubs. During two growing seasons, we inves- tigated gas exchange and growth of newly planted container-grown crapemyrtle (Lagerstroemia indica ‘Victor’), forsythia (Forsythia × inter- media ‘Ly wood’), Vanhoutte spirea (Spiraea × vanhouttei), and photinia (Photinia × fraseri) transplants placed into landscape beds with and without organic mulch. Aſter transplanting, plants were irrigated twice each week at the following rates: 100%, 75%, and 50% of reference evapotranspir tion (ETO). In general, each year, transplants with mulch and transplants receiving 100% or 75% ETO-based irrigation had greater stomatal conductance when compared with transplants without mulch and transplants receiving less irrigation. Growth of transplants followed similar trends. However, it is key to note all transplants survived and appeared healthy throughout the growing season. Even trans- plants receiving 50% ETO were aesthetically pleasing and had growth acceptable for landscape situations. These findings should be useful for landscape irrigation schedu ing and for irrigation managers incorporating water conservation into their landscape maintenance programs. Key Words. Forsythia × intermedia; Lagerstroemia indica; Photinia × fraseri; Reference Evapotranspiration; Spiraea × vanhouttei; Transplant. M.T. Mmbaga and J.B. Oliver Effect of Biopesticides on Foliar Diseases and Japanese Beetle (Popillia japonica) Adults in Roses (Rosa spp.), Oakleaf Hydrangea (Hydrangea quercifolia), and Crapemyrtle (Lagerstroemia indica) ........................................................................................................................ 210 Abstract. This study evaluated efficacy of biopesticides for reducing foliar diseases and feeding damage from Japanese beetle adults on hybrid T rose (Rosa spp.), oakleaf hydrangea (Hydrangea quercifolia), and crapemyrtle (Lagerstroemia indica). The materials tested included house- hold soaps with Triclosan active ingredient (Equate® and Ajax), kaolin clay (Surround®), neem seed oil extract (Triact 70® and Neem Gold®), potassium salt of fatty acids (M-Pede®), horticultural oil (UltraFine® Sunspray oil), and bicarbonate salt (Armicarb®) applied to plants grown under greenhouse, shadehouse, and field conditions. Two fungicides, trifloxystrobin (Strobilurin) and triadimefon (Triazole), and the insecticide carbaryl were included for comparison. All materials tested were effective in controlling black spot (Marssonina rosae, anamorph Diplocarpon rosae) and powdery mildew (Sphaerotheca pannosa) of roses. Kaolin was effective in reducing disease severity of bacterial leaf spot (Xanthomonas campestris) on oakleaf hydrangea and powdery mildew of crapemyrtle. Based on data from repeated trials, the biopesticides were as effective as conventional fungicides in suppressing foliar diseases. Kaolin clay was as effective as carbaryl in controlling Japanese beetle adult feeding dam- age on oakleaf hydrangea, roses, and crapemyrtle, but other products were not effective. Results from this study indicate kaolin clay may be an alternative pro uct to conventional pesticides in foliar diseases and insect pest management for roses, oakleaf hydrangea, and crapemyrtle. Key Words. Black Spot; Fungicides; Insecticides; Japanese Beetle; Pest Management; Powdery Mildew; Xanthomonas Leaf Spot. David J. Nowak, Robert Hoehn, and Daniel E. Crane Oxygen Production by Urban Trees in the United States ....................................................................................... 220 Abstract. Urban forests in the coterminous United States are estimated to produce ≈61 million metric tons (67 million tons) of oxygen annually, enough oxygen to offset the annual oxygen consumption of approximately two-thirds of the U.S. population. Although oxygen production is oſten cited as a significant benefit of trees, this benefit is relatively insignificant and of negligible value as a result of the large oxygen content of the atmo- sphere. Other benefits of the urban forest are more critical to environmental quality and human health than oxygen production by urban trees. Key Words. Air Quality; Environmental Quality; Tree Benefits; Urban Forests. ©2007 | International Society of Arboriculture | ISSN:1935-5297
May 2007
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