Biology Reference
In-Depth Information
several inches upward and down into roots.
Scattered dark pycnidia are present in stems, pet-
ioles, leaf blades, and seed capsules, the latter
probably spreading the blight. Crowns are some-
times developed in a cottony weft of mycelium;
perithecia develop on decaying stems. Remove
and destroy diseased plants; use seed from
healthy plants.
Diaporthe phaseolorum
Lima Bean Pod
Blight
,
Leaf Spot
, apparently native in New Jer-
sey, where it was first noticed in 1891, more
abundant on pole than on bush beans. Leaf spots
are large, irregular, brown, often with discolored
borders and large black pycnidia formed in con-
centric circles in dead tissue. Necrotic portions
may drop out, making leaves ragged.
Pod lesions spread; pods turn black and wilted,
with prominent black pycnidia. Seeds are shriv-
eled or lacking. Spores are produced in great
numbers, are disseminated by wind and pickers,
and enter through stomata or wounds. The dis-
ease is most severe along the coast; optimum
temperature is around 80
F. The fungus is seed-
borne, but most lima bean seed is produced where
the disease does not occur. Use healthy seed;
clean up refuse; rotate crops.
Diaporthe phaseolorum var. sojae
Soybean
Pod
and
Stem Blight
, widespread. This disease
was formerly confused with the more acute stem
canker caused by
D. phaseolorum
var.
caulivora
(
Delphinella
Ascomycetes, Dothideales
Delphinella balsameae
Tip Blight
of fir.
Dendrophoma
Deuteromycetes, Coelomycetes
Pycnidia dark or light brown, superfcial or sub-
merged and erumpent; globose or elongate,
ostiolate; conidiophores elongated, branched;
conidia hyaline, one-celled, elongate to ellipsoid;
parasitic or saprophytic.
Dendrophoma obscurans (see
Phomopsis
obscurans
).
Strawberry Leaf Blight
,
Angular
Leaf Spot
. The lesions are large, circular to angu-
lar, reddish purple, zonate with age, having a dark
brown center, a light brown zone, and a purple
border. Spots may extend in a V-shaped area
from a large vein to edge of the leaf, with black
fruiting bodies appearing in the central portion.
Not serious before midsummer, the disease may
be destructive late in the season. The fungus
winters on old leaves.
Phomopsis obscurans (formerly
Dendrophoma
obscurans
).
Strawberry Leaf Blight
,
Angular
Leaf Spot
.
▶
Rots
). The pod blight is a slower disease,
killing plants in later stages of development. It
can be identified by the numerous small black
pycnidia scattered over the pods and arranged in
rows on stems. The blight is more serious in wet
seasons. The fungus winters on the seed and on
diseased stems in the field. Use clean seed; clean
up plant refuse; rotate crops.
Diaporthe phaseolorum var. caulivora
Stem
Blight
of soybean; also causes pod and seedling
blight, stem canker, and seed decay of soybean.
Diaporthe vaccinii
Blueberry Twig Blight
. The
same fungus that causes cranberry rot blights new
shoots of cultivated blueberries, entering at tips,
progressing toward the base, and ultimately gir-
dling old branches. Pycnidia develop on leaves
and dead twigs. The disease is seldom serious
enough for control measures.
▶
Diaporthe
Ascomycetes, Diaporthales
Perithecia in a hard black strom a made up of host
and fungal elements, first immersed, then
erumpent; ascospores fusoid or ellipsoid, two-
celled, hyaline. Anamorph state a
Phomopsis
with two types of spores; alpha conidia, hyaline,
one-celled ovate to fusoid, and beta conidia,
curved or bent stylospores.
Diaporthe arctii
Diaporthe Blight
of Larkspur,
Stem Canker
, on annual larkspur and delphin-
ium. Lower leaves turn brown and dry but remain
attached; brown lesions at base of stems extend
