Biology Reference
In-Depth Information
Alternaria alternata (formerly
Alternaria
fasciculata
).
Leaf Spot
on rose-acacia and
asclepiodora.
Alternaria alternata (formerly
Alternaria
tenuis
).
Leaf Spot
of magnolia, hibiscus, clarkia,
and many ornamental and other hosts. The fungus
is a general saprophyte and an occasional weak
parasite. It discolors beet, chard, and spinach
seed.
Alternaria
holes; there is more or less defoliation. The fun-
gus is sometimes secondary following bacterial
infection or midge infestation. Rake up and burn
fallen leaves.
Alternaria
Alternaria
leucanthemi
).
Leaf Spot
on shasta daisy, and
Canada thistle.
Alternaria citri
Cherry Leaf Spot
, occasional,
more often a rot of citrus fruits.
chrysanthemi (see
▶
▶
Rots
.
angustiovoidea
Leaf
Spot
and
Alternaria
fasciculata (see
Alternaria
▶
Blight
of leafy spurge.
Alternaria brassicae (with large spores) and
A. brassicicola (with small spores).
Black Leaf
Spot
of crucifers, cabbage, Chinese cabbage,
collards, turnip, garden cress, mustard greens,
radish, and horseradish;
Head Browning
leaf
and pod spot of cauliflower;
Damping-off
,
Wire-
stem
of seedlings.
Seedlings are subject to pre-or post-emergence
damping-off, with dark brown to black sunken
spots on cotyledons, narrow dark spots on stems,
followed by wire-stem, a blackening toward the
base. Leaf spots are small, circular, yellowish,
enlarging in concentric circles with a sooty black
color from the spores. In storage the spots unite to
form a moldy growth over the entire leaf. On seed
pods, spots are purplish at first, later brown; in
moist weather entire pods may be infected.
Cauliflower infection is a browning of the head,
starting at the margin of an individual flower or
cluster. Spores are blown, splashed by tools,
spread on feet of men and animals. Seed bears
spores externally, mycelium internally. Wounds
are not necessary for infection.
Control
Hot water treatment of seed, 122
F for
30 min, is fairly effective. Use long rotation for
cauliflower, avoiding all other crucifers in inter-
mediate years.
Alternaria brassicicola
Leaf Spot
on Thlaspi.
Alternaria brassicicola (formerly
Alternaria
oleracea
).
Cabbage Leaf Spot
, occasional
on
alternata
).
Leaf
Spot
on rose-acacia
and
asclepiodora.
Alternaria leucanthemi (formerly
Alternaria
chrysanthemi
).
Leaf Spot
on shasta daisy, and
Canada thistle.
Alternaria longipes
Brown Spot
of tobacco,
including ornamental flowering tobacco. Small
spots on lower leaves rapidly enlarge and turn
brown. The fungus winters on old stalks, which
should be removed and burned.
Alternaria
Alternaria
brassicicola
).
Cabbage Leaf Spot
, occasional
on crucifers.
Alternaria panax
Leaf Spot
of
oleracea (see
▶
schefflera,
Dizygotheca
, and
Tupidanthurs
.
Alternaria passiflorae
Brown Spot
of passion
flower. Minute brown leaf spots, enlarging to an
inch across are concentrically zoned with various
shades of brown. Dark green water-soaked spots
on fruit turn brown; the fruit shrivels, but the
spots stay firm.
Alternaria polypodii
Fern Leaf Spot
. Brown,
circular to ovate, concentrically zonate spots
are formed along margins of fronds. Chains of
spores are spread by syringing or air currents.
Keep foliage dry; remove and burn diseased
leaves.
Alternaria raphani
Radish Leaf Spot
. Yellow
spots with black sporulation, often with centers
dropping out. Also occurs on turnip.
Alternaria sonchi
Leaf Spot
of lettuce, esca-
role, endive, and chicory.
Alternaria tagetica
Leaf Spot
of marigold.
Alternaria tenuis (see
▶
crucifers. Has
been
confused with
A. brassicicola
.
Alternaria catalpae
Catalpa Leaf Spot
, wide-
spread in rainy seasons. Small, water-soaked
spots, up to 1/4 inch, appear over the leaf; they
turn brown and sometimes drop out leaving shot
Alternaria alternata
).
Leaf Spot
of magnolia, hibiscus, clarkia, and
many ornamental and other hosts.
Alternaria tenuissima
Leaf Spot
on blueberry.
