Air pollution damages white ash. It is rated as sensitive to ozone and is severely injured by stack gases from soft coal consumption and from industrial processes, both of which emit sulfur dioxide.
Two leaf spot fungi, Mycosphaerella effigurata and M. fraxinicola, are common in nurseries and in the forest and cause premature defoliation of white ash. Anthracnose (Gloeosporium aridum) also causes premature defoliation and is most serious following exceptionally wet springs. An ash strain of tobacco ringspot virus causes chlorotic areas on the leaves and has been associated with ash dieback.
A rust (Puccinia peridermiospora) distorts petioles and small twigs. Cankers caused by Nectria galligena may cause branches to break but are rarely found on main stems. Heartwood rots may be caused by Perenniporia fraxinophilus, Phellinus igniarius, Pleurotus ostreatus, Tyromyces spraguei, and Laetiporus sulphureus. These organisms usually enter through wounds or broken branches, mainly on older trees.
Of 26 species of nematodes reported from the roots or root zones of white ash, only one, Meloidogyne ovalis, has been associated with root injury. However, nematodes can be vectors for the ringspot virus (5).
Of the insect pests, the oystershell scale (Lepidosaphes ulmi) is the most serious. Severe infestations cause yellowing of the leaves, and if prolonged, may kill some trees. The cottony maple scale (Pulvinaria innumerabilis) also attacks white ash.
The brownheaded ash sawfly (Tomostethus multicinctus) and the blackheaded ash sawfly (Tethida cordigera) are defoliators that are of concern mainly on ornamental trees. The forest tent caterpillar (Malacosoma disstria) and the green fruitworm (Lithophane antennata) feed on forest trees and occasionally cause complete defoliation within small geographic areas. The larvae of sphingid moths-Sphinx chersis (the great ash sphinx), S. kalmiae, and Ceratornia undulosa-feed on the leaves of white ash, as does the notched-wing geometer (Ennomos magnaria). The larvae of two leaf roller moths, Sparganothis dilutocostana and S. folgidipenna, also feed on ash.
The ash bark beetle (Leperisinus aculeatus) may cause slight injury when the adults bore into the bark to hibernate. The ash borer (Podosesia syringae) may seriously damage young shade and shelterbelt trees. The ash and privet borer (Tylonotus bimaculatus) attacks and kills branches, especially on older trees. Both the red-headed ash borer (Neoclytus acurninatus) andthe banded ash borer (N. caprea) colonize cut logs and dead or dying trees (1).
White ash seedlings are easily damaged or destroyed by deer and cattle browsing. Rabbits, beaver, and porcupine occasionally use the bark of young trees for food.
- Burns, Russell M., and Barbara H. Honkala, technical coordinators. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654 (Supersedes Agriculture Handbook 271,Silvics of Forest Trees of the United States, 1965). U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 pp. http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm
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