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Ecology and Epidemiology

Infection, Epidemiology, and Control of Diplodia Blight of Austrian, Ponderosa, and Scots Pines. Glenn W. Peterson, Plant Pathologist, Rocky Mountain Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, Lincoln, NE 68503; Phytopathology 67:511-514. Accepted for publication 13 October 1976. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-511.

Infection of vegetative shoots of Austrian, ponderosa, and Scots pines by Diplodia pinea preceded infection of pollen cones. Pollen cones were seldom infected. Second-year seed cones of the three pine species became infected as early as late May; first-year seed cones were not infected. Infected seed cones were commonly observed on trees with noninfected shoots. Pycnidia developed extensively on second-year seed cones and needles in the autumn of the year of infection if late summer rain was plentiful, but not until spring if rainfall was below normal. Diplodia pinea on Austrian pines in eastern Nebraska was controlled by two applications of Bordeaux mixture applied within a 2-wk period (about 24 April - 8 May) beginning with bud expansion; later applications were ineffective. The early applications of fungicide to control shoot infection did not prevent infection of second-year seed cones.

Additional keywords: Pinus nigra, P. ponderosa, P. sylvestris.