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- Author or Editor: R. D. Durbin x
Seedlings of red oak (Quercus rubra L.) grown in various planting media without nutritional supplements developed marginal necrosis and puckering on their first whorl of leaves. These symptoms were prevented by supplying Ca++ to seedlings growing in a vermiculite-peatmoss mixture. An exogenous supply of Ca++ was also required for initial growth in silica sand.
The reaction of 39 marigold cultivars to Pseudomonas syringae pv. tagetis Young, Dye & Wilkie was determined. Three new symptoms were observed in addition to large necrotic leaf spots with or without apical chlorosis: flecks and leaf spots both surrounded by chlorotic halos and apical chlorosis without leaf spots. Symptoms develop only on vegetatively growing tissue; new symptoms do not develop on mature tissue. Tall cultivars generally were more susceptible than dwarf cultivars.