City Trees

January/February 2013

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A Closer Look at the Gloomy Side of Red Maple by Bob Polomski, J. C. Chong, and George Dickert Photos by George Dickert Red maple (Acer rubrum) is one of the most widely planted shade trees in urban environments: landscapes, streetscapes, parking lots, buffer strips, and parks. Members of the genus Acer comprise 15 to 57% of the street trees planted in 12 large cities in eastern North America (Raupp et al. 2006). There are about 30 red maple cultivars currently in production in the southern U.S. nurseries (Frank et al. 2012), among which October Glory® ('PNI 0268') and Red Sunset®('Franksred'), introduced in 1961 and 1966, respectively, are the two most widely grown cultivars. It helps that red maples, especially cultivars, offer four seasons of interest, including early spring flowers and Urban environments are tough, and the gloomy scale only adds to the stress as evidenced by the dieback in the crown of this tree. ing conditions and encountering a willing and able pest. That pest is gloomy scale (Melanaspis tenebricosa). Detailed view of layers of gloomy scale on the scaffold branches of red maples in downtown Spartanburg, South Carolina smooth silvery-gray bark on young trees. Red maples have the signature trait of vibrant fall colors that range from pure yellow to vivid red and burgundy. An added bonus is their ease-of-propagation and rapid growth rate—10 to 12 feet tall (3.1 to 3.6 m) in 5 to 7 years (Frank et al. 2012). Red maples have become ubiquitous in our towns and cities, prized for the belief that they can tolerate hostile urban conditions including above- and below-ground space limitations, compacted soils, air pollution, road salt, and pest pressures. Just like "A man's got to know his limitations" (Harry "Dirty Harry" Callahan in Magnum Force, 1973), we are now seeing that red maples have limitations. Their inability to cope with physical, chemical, and biological adversities has resulted in the perfect storm: stressed trees growing in inhospitable grow- 32 Over the past 5 to 10 years we have noticed an increased occurrence and severity of gloomy scales infesting red maple. Sure, there are other pests that attack red maples, such as aphids, ambrosia beetles, borers, cottony maple scale, obscure scale, borers, and tar spot, but gloomy scale has become the Achilles heel of red maple. Gloomy scale can be found from Texas to Florida and north to Michigan and Pennsylvania. They commonly attack the soft maples, such as boxelder, red maple and silver maple. Gloomy scale insects overwinter as mated females. The 1/16th inch (1.6 mm) wide, yellowish or pink to purple, legless, and wingless females have convex armor or shell that often resembles the color of the bark, which makes an infestation difficult to detect. Egg-laying occurs in late May and within two days of oviposition, the young crawlers emerge. The tiny (1/64th inch/.4 mm long), cream-colored mobile crawlers immediately seek out feeding sites, often near twig unions and buds. They insert their piercing-sucking mouthparts into the tissue and begin to feed in the phloem tissues. City Trees

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