Blights - Westcott's Plant Disease - page 131

Septoria apiicola (Syn. Septoria apii and
S. apii-graveolentis) Celery Late Blight , gen-
eral on celery, also on celeriac. The two species,
singly or together, produce the disease known as
late blight, first reported in Delaware in 1891 and
since causing much crop destruction, one
California county reporting half a million dollars
loss from celery blight in 1908 and Michigan
a million in 1915. It was not known until 1932
that two distinct species were involved.
Early symptoms are similar. Large leaf spot,
due to S. apii , starts as a light yellow area, which
soon turns brown and dies. Spots are up to 1/4
inch in diameter, with small black pycnidia. In
small leaf spot, due to S. apiigraveolentis , the
more common and destructive pathogen,
pycnidia appear at the first sign of chlorotic spot-
ting and are often outside of the indefinite mar-
gins of the spots, which are not over 2 mm. If
infection is severe, the spots fuse, and the leaves
turn brownish black and rot. Leaf stalks may also
be infected. Pycnidia winter on seed and in plant
refuse in garden and compost. A single pycnid-
ium of the small-spot fungus has an average of
3675 spores, extruded in gelatinous tendrils.
A single leaf spot may average 56 pycnidia, and
a single plant may have 2000 spots. Thus there
are enormous amounts of inoculum to be spread
by rain, insects, people, and tools. Some years
ago on Long Island, when celery was inter-
cropped with spinach, it was found that workers
spread blight spores on their sleeves as they cut
the spinach in early morning dew. And there is
a case on record where a man walked through his
own blighted celery before taking a diagonal path
across his neighbor's healthy field. In a few days
blight showed up all along that diagonal path.
Control The fungus usually dies in the seed coat
while the seed is still viable. Using celery seed
more than 2 years old obviates the necessity for
treatment. Fresh seed can be soaked in hot water
for 30 min at 118 to 120 F. Use crop rotation; do
not plant near where celery was grown the year
before. Spray with bordeaux mixture or a fixed
copper, starting in the seedbed when plants are
just out of the ground.
Septoria leucanthemi* Leaf Blight , Blotch on
chrysanthemum, shasta daisy, and oxeye daisy.

The generally destructive Septoria on chrysan-
themum is S. chrysanthemi . ▶ Leaf Spots .
Septoria petrosellini Leaf Blight of parsley, sim-
ilar to late blight of celery but confined to parsley.
*Recent study indicates these are one species
and that the name should be S. apiicola .

Septotinia

Ascomycetes, Helotiales,
Sclerotiniaceae

Stroma a definite, small, thin, elongate to angular
black sclerotium maturing in host tissue after it
has fallen to ground. Apothecia shallow cup-
shaped, stipitate; spores hyaline, ovoid, one-
celled. Conidial stage a Septotis , with hyaline
spores, two or more cells, formed on sporodochia.
Septotinia podophyllina Leaf Blight of may-
apple, found on leaves and stalks of this plant only.

Servazziella

Ascomycetes, Amphisphaeriales

Perithecia immersed in a stroma, with long necks
converging into a disc; ascospores long, filiform,
hyaline; conidia on a stroma.
Cryptospora longispora (see

Servazziella
longispora ). Araucaria Branch Blight.
Servazziella longispora (formerly Cryptospora
longispora ). Araucaria Branch Blight. Lower
branches are attacked first, with disease spread-
ing upward; tip ends are bent and then broken off;
plants several years old may be killed. Prune off
and burn infected branches.

▶

Sirococcus

Deuteromycetes, Sphaeropsidales,
Sphaerioidaceae.

Small, rounded, black, semi-immersed pycnidia
with wide ostioles; conidia hyaline, fusiform,
slightly constricted, 1-septate.