Abstracts

JACOBI, W.R. 1989. Populus problems. Am. Nurseryman 169(2):48-55.

Foliage diseases can reduce the aesthetic value of Populus species. Though leaf diseases look bad, they are not generally life-threatening to trees. This article describes five of the most common leaf spots found on Populus species: Marssonina leaf spot; ink spot of aspen; leaf and shoot blight; leaf rust; and Septoria leaf spot. Most native and hybrid poplars are susceptible to one or more of these diseases. My discussion of the disease’s symptoms and life cycles is followed by some general tips for control.

ANONYMOUS. 1988. The effects of ozone on landscape plants. Landscape Contractor, October, pp 8-10.

When pollutants combine in sunlight, the resultant ozone is very unstable and rapidly causes oxidation on such varied surfaces as metals, paints and landscape plants. Ozone enters the stomates. Ozone is a very strong oxidizer, so it affects the membranes of the cells within the leaf whose stomates it has entered. When these membranes are damaged, they die. Some plants have much better ability than others to resist ozone because their stomates are smaller, so they are better able to keep the toxic gas out of their inner workings.

• © 1990, International Society of Arboriculture. All rights reserved.