Abstracts

McCREARY, D.D. 1990. Blue oaks withstand drought.California Agriculture 44(2): 15-17.

In mid-August 1987, many oak trees in California began turning brown and dropping their leaves. Most observers felt the reason for the trees changing color so early was drought. This is consistent with knowledge Of tree physiology. A study was undertaken to identify; some of the effects of drought on blue oak trees. The initial analysis examined whether or not there were significant relationships between the degree of defoliation and subsequent growth and development, including survival, acorn production, and leaf-out date. All 200 trees survived both years’ defoliations and leafed out the following springs. Defoliated trees tended to leaf out earlier than those that remained green. The results of this study suggest that summer defoliation of blue oaks from drought has little short-term impact on growth or survival. California’s blue oaks are apparently well adapted to withstand the adverse effects of periodic droughts.

BOOTH, D.C., T. SMILEY and B.R. FRAEDRICH. 1990. New technology from IPM programs. Arbor Age 10(2): 12-14,16.

IPM provides early detection and spot treatment of insects, mites, diseases, and cultural problems. The major goal of a tree-and-landscape IPM program is improved plant care with reduced chemical usage. The following new technology represents developments currently available to the arborist to help meet this goal: Horticultural Spray Oils Insecticidal Soap, Natural Insecticides, Biological Control, Pyrethroids, Plant Disease Detection, Slow-Release Nitrogen Fertilizers, pH Testing, Foliar Nutrient Analysis and Soil Aeration Machines. New developments will continue to refine and improve the IPM technology available to the arborist. The challenge for IPM programs in the 1990s will be to improve our ability to detect problems and treat them with the least possible environmental impact.

• © 1991, International Society of Arboriculture. All rights reserved.