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Street trees are an important factor in the attractiveness of residential streets. However, large, older trees that are the most attractive to the public are not necessarily the most desirable from a silvicultural point of view. Shade tree commissions, apparently formed in response to losses in esthetically valued trees, can create tree distributions that are less prone to catastrophic losses of attractive trees. Factors other than street trees also contribute to street esthetics and should be considered in shade tree management.

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Populations of Tetranychus atlanticusMcGregor, on detached leaf discs from soybean plants in sand culture were greatly influenced by the amount of supplied nitrogen. Two nutrient formulae were used in which the balance of the ions were quite different. Increasing the nitrogen in either formula increased the population. The effects of supplied phosphorus or potassium seemed to depend on the interrelationship of ions in the nutrient solution.Varying the phosphorus concentration in one formula did not alter the number of progeny of this species. A much higher concentration of phosphorus than the standard level in the second formula resulted in a higher population. Differences in mite population resulting from various concentrations of potassium were not significant. The age of the soybean leaf, as indicated by its position on the plant, was found to influence the number of progeny of this species, with larger populations developing on the younger leaves.Studies of several phytophagous mites have indicated that the nutritional state of the host plant affects the mite population. Generally these studies have compared populations developing, under otherwise standardized conditions, on hosts supplied with various levels of nutrient ions. The mites involved were Tetranychus urticae Koch on the foliage of apple, cucumber, lima bean and tomato; Panonychus ulmi (Koch) on that of apple; and Bryobia praetiosa Koch on that of lima bean. In some cases a direct relationship was noted between the number of progeny and the level of nitrogen in the nutrient supplied to the host plant, while in other instances an opposite response was reported. In certain cases either deficient or excess phosphorus or potassium was reported to have an effect. The findings of these investigators will be discussed in connection with the results of our studies, which were conducted to determine what effect various levels of nitrogen, phosphorus, and potassium, supplied to soybean plants, would have on the production of progeny ~) Published as Miscellaneous paper No. 478 with the approval of the Director of the Delaware Agricultural Experiment Station, Publication 349 and Scientific Article 365 of the