Biology Reference
In-Depth Information
flowers may be due to
Botrytis cinerea
, which
produces a sparser mold and conidiophores
projecting farther from the petal or leaf surface.
Conidia are blown by wind, splashed by rain,
carried on gardeners' tools, and sometimes
transported by ants. Secondary infection is abundant
in cool moist weather. In late summer small, shiny
black, slightly loaf-shaped sclerotia are formed near
the base of stalks, just under the epidermis. They are
quite different from the large, flat, black sclerotia
oftenformedby
B. cinerea
onthesamestalks.
Control
Sanitation is the most important step.
Cut down all tops in autumn at ground level, or
just below, to get rid of sclerotia wintering near
base of stems. Burn this debris; never use it for
a mulch. Avoid any moisture-retentive covering.
If you insist on manure, apply it in a wide ring
around the plant, well outside the area of emerg-
ing shoots. Go around with a paper bag periodi-
cally, cutting off for burning all blighted parts;
never carry these parts loose through the garden
for fear of shedding spores to healthy plants.
Botrytis polyblastis
▶
Fig. 3
Botrytis Blight on Tulip
flower stems or bulbs. Sometimes the latter have
yellow to brown, slightly sunken, circular lesions
on outermost fleshy scales without the formation
of sclerotia. Spring infection comes from spores
produced on such bulbs or from sclerotia on bulbs
or sclerotia left loose in the soil after infected
tissues have rotted.
Control
Inspect all bulbs carefully before plant-
ing; discard those harboring sclerotia or suspi-
cious brown lesions. It is wise, though seldom
possible in a small garden, to plant new bulbs
where tulips have not grown for 3 years. Plant
where there is good air circulation. Make periodic
inspections, starting early, removing into a paper
bag plants with serious primary infection and
blighted leaves. Cut off all fading flowers before
petals fall; cut off all foliage at ground level when
it turns yellow. Burn all debris.
Streptobotrys arisaemae (formerly
Botrytis
streptothrix
) (teleomorph state
Streptotinia
arisaemae
).
Leaf
and
Stalk Blight
of Jack-in-the-
pulpit and golden club. This species has conidio-
phores with strikingly twisted branches, produc-
ing a reddish brown mat of conidia. Sclerotia are
very small, seldom over 1/32 inch, black, shiny,
and somewhat hemispherical.
Sclerotinia polyblastis
.
Botrytis
Streptobotrys
arisaemae
) (teleomorph state
Streptotinia
arisaemae
).
Leaf and Stalk Blight
of Jack-in-
the-pulpit and golden club.
Botrytis tulipae
Tulip Fire
,
Botrytis Blight
of
tulips, general wherever tulips are grown, causing
much damage in rainy springs. The first indica-
tion of disease is the appearance of a few mal-
formed leaves and shoots among healthy tulips or
large light patches resembling frost injury on
leaves. Gray mold forming on such blighted
areas of plants grown from infected bulbs pro-
vides an enormous number of conidia to be
splashed by rain to nearby tulips. Secondary
infection appears as minute, slightly sunken, yel-
lowish leaf spots, surrounded with a water-
soaked area, and gray to brown spots on stems,
often zonate, and resulting in collapse. Small
white spots appear on colored flowers, brown
spots on white petals (see
Fig. 3
); but with con-
tinued moisture the spots grow together, and in
a day or so the fuzzy gray mold has covered rotten
blooms and large portions of blighted leaves.
Very small, shiny black sclerotia are formed in
leaves and petals rotting into the ground, or on old
streptothrix
(see
▶
Briosia
Deuteromycetes, Hyphomycetes
Conidia on synnemata or coremia, erect fascicles
of hyphae ending in a small head; spores globose,
dark, one-celled, catenulate (formed in chains).
