Control. Spray with commercial lime-sulfur at a 1 to 80 dilution when
buds burst in spring; repeat 2 weeks later. After shoots develop you can
use sulfur dust or a wettable sulfur spray.
EUONYMUS MILDEW (Oidium euonymus-japonici),
general throughout the
South and on the Pacific Coast. The mycelium forms a thick felt
on leaf surfaces, and there is some yellowing and defoliation. Syringing
with the hose often reduces damage. Spray or dust with sulfur.
LILAC MILDEW (Microsphaera alni),
also found on alder and other trees,
shrubs and vines, on deciduous azaleas, privet, etc. The disease is
common in late summer and fall; lilac foliage is often completely covered with a thin white coating dotted with myriads of black perithecia.
Control. Dust shrubs with sulfur or apply copper sprays if you think
the result worth the effort. The mildew is unsightly, but it appears so
late in the season it has little effect on general plant health.
PHLOX MILDEW (Erysiphe cichoracearum).
This species also affects cucurbits, causing terrific losses in melons grown commercially in the
Southwest, and it is common on many of our flowers by late summer,
including aster, chrysanthemum, dahlia, delphinium, golden-glow, and
zinnia. On phlox the white coating appears on variety Miss Lingard in
June but becomes prominent on other varieties in July and August (in
New Jersey). The mycelium covers both leaf surfaces, often the stem
as well, and is thickly and conspicuously studded with black perithecia
Control. Sulfur dust is still an excellent specific for mildews but should
not be used on melons and squashes. Resistant melon varieties have been
developed. Copper sprays are useful, and I usually depend on the ammoniacal copper in Tri-ogen, using it for phlox, chrysanthemums, zin-
nias, etc., when I have it made up for roses.
ROSE MILDEW (Sphaerotheca pannosa var. rosae).
In the semi-arid sections
of the Southwest and the Pacific Coast this is the most important
rose disease, and it ranks next to black spot in the East. In my section
it may appear as early as April, as soon as new leaves develop, and is
well established by mid-May on Dorothy Perkins and other rambler roses,
often entirely preventing bloom. It is present on hybrid teas and floribundas by June but flourishes best on these in late summer when we
have cool nights.