Elm. Parts of the crown suddenly wilt and wither. Terminal twigs bend upward like shepherds’ crooks. Examination of the sapwood in dead members will show brown stria-tions. This is probably Dutch elm disease, identifiable positively only in the laboratory because other, less lethal wilts closely resemble it. The causative fungus is transmitted by a small, dark-brown bark beetle which breeds in dead or dying elm wood, all of which should be removed (including old brush or log piles) and burned, or debarked and sprayed with lindane. The bark beetle's presence in elms will be signaled by bird-work on invaded branches. Some trees die quickly, others linger. There is no cure, only prevention by pruning and well-timed spraying, which should aim also to control the greenish elm leaf beetle whose defoliation weakens the trees. Feeding, and keeping their soil's pH high, may raise the trees' resistance to Dutch elm disease.

Reliable textbooks on tree pest, parasites, symptoms, and control measures include the following:

Tree Maintenance, P. P. Pirone (Oxford University Press); Tree Care, John M. Haller (The Macmillan Co.); Insects and Diseases of Ornamental Trees and Shrubs, Ephraim Porter Felt and W. Howard Rankin (The Macmillan Co.); Diseases and Pests of Ornamental Plants (Third Edition), B. O. Dodge, H. W. Rickett, and P. P. Pirone (The Ronald Press Co.); The Wise Garden Encyclopedia, E. L. D. Seymour, ed. (William H. Wise& Co.).