Blights - Westcott's Plant Disease - page 101

lowest leaves and works up the stem until all
leaves are blackened and hanging limp. This is
the result of many spot infections and not from an
invasion of the vascular system.
Buds rot or open to distorted flowers with
irregular brown flecks. There are sometimes
severe stem lesions, but the rot rarely progresses
into the bulbs. Spores formed in the usual gray-
mold masses in blighted portions are spread by
rain, air currents, and gardeners. Optimum spore
germination is in cool weather, around 60 F, but
once infection has started 70 F promotes most
rapid blighting. With sufficient moisture the
cycle may repeat every few days through the
season. The fungus winters as very small black
sclerotia, irregular or elliptical in shape, in fallen
flowers or blighted dead stems and leaves, or as
mycelium in the basal rosette of Madonna lilies.
Control Avoid too dense planting, and shady or
low spots with little air circulation and subject to
heavy dews. Clean up infected plant parts before
sclerotia can be formed. Copper sprays are more
effective for the lily Botrytis than the newer
organics. Spray with bordeaux mixture; start
when lilies are 5 or 6 inches high and continue
at 10-to 14-day intervals until flowering.
Botrytis galanthina Botrytis Blight of snow-
drop, sometimes found in the sclerotial state on
imported bulbs. If the black dots of sclerotia are
present only on outer scales, remove scales
before planting; otherwise discard bulbs.
Botrytis gladiolorum Gladiolus Botrytis Blight ,
Corm Rot , first reported in Oregon in 1939 and
now serious in all important gladiolus-growing
areas - the Pacific Coast, the Midwest,
Florida - in cool, rainy weather. In northern
areas the disease is a corm-rotting problem, in
the South a flower blight, damaging in transit, and
in all areas it is a leaf spot or blight.
In dry weather and in more resistant varieties
the leaf spots are very small, rusty brown,
appearing only on the exposed side of the leaf.
In more humid weather the spots are large,
brown, round to oval or smaller, pale brown
with reddish margins. Flower stems have pale
brown spots that turn dark. There may be a soft
rotting at the base of florets. The disease starts on
petals as pinpoint, water-soaked spots, but in

moist weather the whole flower turns brown and
slimy. Flowers with no visible spotting when
packed often arrive ruined. After the flowers are
cut, infection spreads down the stalk and into the
corm, producing dark brown spots, irregular in
shape and size, most numerous on the upper sur-
face. Corms may become soft and spongy with
a whitish mold. Oval, flat, black sclerotia, 1/8 to
1/4 inch long, are formed on corms in storage and
in rotting tissue in the field or in refuse piles. They
may persist in the soil several years.
Control Cure corms rapidly after digging; bury
or burn all plant refuse.
Botrytis hyacinthi Hyacinth Botrytis Blight
recently found in Washington on plants grown
from imported bulbs. Leaves have brown tips
with gray mold or brown spots on lower surface.
Leaves may be killed, with small black sclerotia
formed in rotting tissue. Flowers rot and are cov-
ered with powdery gray spores. Do not work with
plants when they are wet; remove infected parts
or whole plants.
Botrytis narcissicola ▶ Sclerotinia

narcissicola , under Rots.
Botrytis paeoniae Peony Botrytis Blight , Early
Blight , Bud Blast , Gray Mold , probably present
wherever peonies are grown. It is also recorded
on lily-of-the-valley, but that may be a form of
Botrytis cinerea . Peony blight was first noticed in
epiphytotic form in this country in 1897 and has
been important in wet springs ever since.
Young shoots may rot off at the base as they
come through the ground or when a few inches
high, with a dense velvety gray mold on the
rotting portions. This early shoot blight is far
more common when the young stems are kept
moist by having to emerge through a mulch of
manure or wet leaves. Flowers are attacked at any
stage. Buds turn black when they are very tiny,
never developing, or they may be blasted when
they are half open. If it is dry in early spring,
infection may be delayed until flowers are in
full bloom, at which time they turn brown. Infec-
tion proceeds from the flower down the stem for
a few inches, giving it a brown and tan zoned
appearance. Leaf spots develop when infected
petals fall on foliage. Continued blighting of
leaves through the summer and late blasting of