Abstracts

HALL, R.W., A.M. TOWNSEND and J.H. BARGER. 1988. Resistance of 13 species of elm leaf beetle. Am. Nurseryman 168(5):93-94.

Elm leaf beetle has become a major defoliator of elms in cities. We tested 13 tree species to determine their suitability as host for this pest. We found that European species were generally better hosts to the beetle that Asian and American species. Susceptibility by species, with regions of origin, are: Relatively low: parvifolia and Zelkova serrata, Asia, Moderate: U. davidiana japonica, U. pumila and U. wilsoniana, Asia: U. americana, U. rubra and U. thomasii, America, U. laevis, Europe; and U. ‘204’, a cross between U. carpinifolia and U. parvifolia, High: U. laciniata, Asia; U. carpinifolia and U. glabra, Europe.

HAMILTON, W.D. 1988. Tree stress in the urban environment. Arbor Age 8(8): 40, 42.

I have studied stresses from the effects of mechanical damage to trees; from pruning methods, pests, weeds, soil salt, and air pollutants, as well as the effects of comparatively warm winters on subsequent growth. I want to discuss how climate-induced stresses have affected the trees’ resistance to diseases and insects. Trees endure many different kinds of stresses in the urban environment, but the influence of central California climatic extremes since 1971 has been particularly noteworthy. It is no surprise that several insect and disease problems erupted after consecutive years of drought and warm, wet winters. The long series of climatic extremes in our recent past does not preclude a more normal weather pattern in the future. But this year many states have been afflicted by one of the most severe droughts of the century. The essential lesson for landscape installers and managers seems clear: Provide optimum conditions for root growth and avoid extremes of management. This along with the appropriate use of intelligent management and new research information to maintain vigor, offers the best opportunity for acceptable results in the future.

• © 1989, International Society of Arboriculture. All rights reserved.