Abstracts

WICK, ROBERT L. 1986. Careful specimen selection helps plant disease diagnosis. Am. Nurseryman 164(4): 79-80, 82-85.

Of paramount importance for accurate diagnosis of plant disease is a fresh and adequate specimen and a complete case history of the plant’s problem. Remember the following points when collecting specimens and information for plant-disease diagnosis. The part of a plant showing symptoms may or may not be the primary site where disease began. When this is the case, foliage or branch samples are of no diagnostic value because the primary problem occurs in the root system. Soil type, environmental conditions, cultural practices, parasitic organisms and the plant itself all interact to influence the health of the plant. For cooperative extension or private consultants to accurately assess the importance of the factors and give meaningful recommendations, a carefully selected specimen accompanied by a case history is necessary. Guidelines for collecting specimens and information are given.

CERVELLI, JANICE A. 1986.Raised containers undermine urban trees and urban design. Am. Nurseryman 164(9): 50-52.

Numerous product advertisements still praise the values of raised tree containers measuring 4 feet by 4 feet. Due to the barren city environments and the many difficulties of planting trees in cities, containers are the only alternative in many cases. However, a re-evaluation of such tree containers is necessary to determine their effectiveness in meeting not only the physiological needs of trees but also the functional and aesthetic requirements of cities. Continued use of surface planters has shown them to be notorious tree killers. Winter root damage is the major limiting factor of containers in the Midwest and Northwest. One researcher has found the cold tolerance of root systems of many woody ornamentals to be less than that of the aerial parts. Trees in containers must also contend with restricted root growth and nutrient availability. Since most feeder roots are in the upper 30 inches of soil, an increase in container depth does not compensate for winter root damage and horizontal root spread. Container trees receive minimal moisture from rainfall and can suffer from leaf scorch, winter dessication and partial defoliation. Lastly, soil mixes with high humus content can subside--compacting to half or less of the original level and significantly reducing soil aeration. This myriad of cultural problems reduces the natural resistance of a container plant to disease and insect infestation as well as its life-span and ultimate size. Large container trees rarely live over 10 years.

• Copyright © 1987, International Society of Arboriculture. All rights reserved.