Azalea Petal Blight
New York Chapter Newsletter
The rainy weekend of June 1 and 2 brought an abrupt end to the rhododendron and azalea flowers in the gardens of many of our members. Petal Blight, long thought to be a problem only in the South was suspected and branches of affected plants were sent to Cooperative Extension Association of Suffolk County. Their report follows: Fieldmans' Report - June 21, 1974.
"Azalea Petal Blight,
Ovulinia azaleae
, took heavy toll on Rhododendron and Azalea flowers this year. Spots enlarged rapidly on June 1st - white on colored petals and brown on white petals. On June 2nd the flowers were mush.
The disease is difficult to diagnose. Gray mold, or Botrytis was eliminated as no conspicuous mycellium within 48 hours was produced. Petal Blight develop sclerotia but are first soft and blue-gray, then 10 - 15 days later are hard, black and 1/8 to 1/4 inch and irregularly shaped. There is no injury to stems, foliage nor stamens which usually remain conspicuously erect on the blighted flower.
Mrs. W. McKay of Kings Park reports that many members of the N.Y. Chapter of the American Rhododendron Society experienced this blight. Some rhododendrons affected were 'E. S. Rank', 'Lee's Dark Purple', 'Marchioness of Landsdowne' and Glen Dale azaleas: 'Glamour', 'Mary Mary Margaret', 'Buccaneer', and 'Rosebud'.
Controls: Remove all infested flowers because this blight can spread rapidly. Spray immediately with Benlate and repeat in 1975 or spray with one of the following fungicides at five-day intervals during bloom: nabam, ferbam, zineb, dichlone, Fore or copper-zinc-chromate complex. Use with spreader sticker for best results."