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Some factors affecting rhododendron bud blast and its control
Author(s) -
HOWELL P.J.,
WOOD R.K.S.
Publication year - 1962
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1962.tb06073.x
Subject(s) - biology , spore , fungicide , fungus , botany , insect , horticulture
SUMMARY In studies of the relationship between rhododendron bud blast, caused by Pycnostysanus azaleae , and the leaf hopper Graphocephala coccinea , laboratory experiments provided no conclusive evidence that the fungus entered the bud tissues through the wound produced by oviposition. The primary brown necrotic lesions of the disease were frequently found to contain the insect's eggs. In the field healthy buds which had been enclosed in muslin to exclude the insect did not become infected. Buds enclosed with the fungus but not the insect showed very few infections. Most infections occurred when both insects and diseased material had been enclosed with the bud. Although the muslin was found not to impede the passage of P. azaleae spores, fewer buds became infected when the insect was enclosed without the diseased material. The possibility that the insects may be contaminated by spores is discussed. Field trials in 1956/57 and 1957/58 showed that the disease could be reduced both by certain fungicides and by a DDT insecticide. A colloidal sulphur spray was the most effective on Rhododendron var. Prince of Wales in both years and had no apparent phytotoxic effects. Some phytotoxicity was shown by Bordeaux mixture and phenyl mercury acetate sprays.