Biology Reference
In-Depth Information
Wolfiporia cocos (formerly
Poria cocos
).
Root
Rot
on roots of various trees, especially pine, in
southeastern United States. Huge sclerotia,
weighing up to 2 pounds, are formed; this stage
is known as
Pachyma cocos
.
brown and wrinkled. The fungus lives in the
soil; primary infection is in the field, secondary
from contact in transit or storage. Sort carefully
before packing. Refrigerate at 45
to 50
Fin
transit.
Pythium aristosporum
Root Rot
of bean.
Pythium arrhenomanes
Root Rot
on tomato,
broadleaf
Pyrenochaeta
signalgrass,
large
crabgrass,
barnyardgrass, nutsedge, goosegrass,
itchgrass
Blights
.
Phoma terrestris (formerly
Pyrenochaeta
terrestris
).
Pink Root
of onions, widespread on
onions, garlic and shallot; also on grasses. Roots
of affected plants shrivel and turn pink. New
roots replacing the old are infected in turn; plants
are stunted, bulbs small. The fungus persists
indefinitely in the soil and is distributed on
onion sets and transplants. Yellow Bermuda is
the most resistant of commercial onion varieties.
The green Beltsville Bunching onion, Nebuka
strain of Welsh onion, Evergreen variety of shal-
lot, and leaks and chives are resistant. In Arizona,
Granex gives a better yield than other onions
despite pink root.
Pyrenochaeta lycopersici
Root Rot
on tomato.
Pyrenochaeta
and johnsongrass.
Pythium carolinianum
Root and Stem Rot
of
parrotfeather (
Myrio-phyllum
).
Pythium catenulatum
Root Rot
of bean.
Pythium debaryanum
Damping-Off
of seed-
lings.
Watery Leak
of potatoes. Leak starts as
a brown discoloration around a wound and soon
spreads to include the whole potato, which is soft,
easily crushed, and drips a brown liquid with the
slightest pressure. Entrance to the tuber is usually
through harvest wounds.
Pythium
hyphae grow
through the soil in great profusion and can enter
seedlings through either stomata or unbroken
epidermis. See
▶
Damping-Off
,
for
rot of
▶
seedlings.
Pythium dissotocum
Root Rot
of bean, and
spinach.
Pythium irregulare Associated with
Melon
Root Rot
and
Fruit Rots
of other cucurbits in
cool weather and
Seed Decay
of corn.
Root Rot
and
Crown Rots
of clovers and basil.
Pythium mastophorum
Damping-off
Phoma
terrestris
).
Pink Root
of onions, wide spread on
onions, garlic and shallot; also on grasses.
terrestris
(see
▶
Pythium
on
celery.
Pythium myriotylum
Root Rot
on tomato.
Pythium paroecandrum
Stem, Crown and
Root Rot
on lupine.
Pythium polymastum
Bottom Rot
Oomycetes, Peronosporales
Wall of sporangium smooth; dischargings warm
spores in imperfectly formed state into thin-
walled vesicle, which later ruptures to allow
spores to escape. Sporangia terminal or interca-
lary. Species live in moist soil causing damping-
off and root rots.
Pythium acanthicum; P. myriotylum; P.
periplocum Causing rot of watermelon fruit.
Pythium aphanidermatum
Leak
,
Root Rot
.
Damping-off of muskmelon, cucumber, squash,
also papaya, bean, radish, spinach, sugar beet,
guayule, caper spurge, and ice plant. There is
a watery decay with a yellow brown liquid
leaking out when fruit is pressed. Lesions are
and
Damping-off
on cabbage.
Pythium splendens On Chinese evergreen, pep-
eromia, and philodendron.
Pythium ultimum
Fruit Rot
of muskmelon,
often with luxuriant white fungus growth;
Damping-Off
,
Root Rot
of many seedlings in
greenhouse and field.
Root Rot
and
Crown Rot
of
clovers.
Crown Rot
of impatiens.
Root Rot
of kiwi.
Pythium uncinulatum
Stunt
and
Leaf
Yellowing
on lettuce.
Pythium spp. Most soils contain several species
of
Pythium
ready to perform at optimummoisture
