Biology Reference
In-Depth Information
vegetables with fleshy roots with leafy varieties.
Avoid bruising at harvest time.
Erwinia chrysanthemi
Bacterial Blight
of
Chrysanthemum, a florists' disease, first noted
in 1950. First evidence of blight is a gray water-
soaked area mid-point on the stem, followed by
rot and falling over. The diseased tissue is brown
or reddish brown; the rot progresses downward to
the base of the stem or, under unfavorable condi-
tions, may be checked with axillary buds below
the diseased area producing normal shoots. Cut-
tings rot at the base. Sometimes affected plants do
not show external symptoms, and cuttings taken
from them spread the disease. Bacteria can be
spread via cutting knife, or fingernails in
pinching, and can live several months in soil.
A form of this species causes a leaf blight of
philodendron and may also infect banana, carna-
tion, corn, and sorghum and pith/stem rot of
tomato.
Control
Snap off cuttings; sterilize soil and
tools.
Corn rot. Corn leaves show light or dark
brown rotting at base; husks and leaf blades
have dark brown spots; lower portion of stalk is
rotten, soft, brown, with strong odor of decay;
plants may break over and die, with little left
but a mass of shredded remnants of fibrovascular
bundles. Bacteria enter through hydathodes
(water pores), stomata, and wounds.
Erwinia cypripedii Reported from California,
causing brown rot of Cypripedium orchids.
Small, circular to oval, water-soaked, greasy
light brown spots become sunken, dark brown to
chestnut. Affected crowns shrivel; leaves drop.
Erwinia herbicola (see
Pantoea herbicola
).
Leaf Spot
of dracaena. On Dracaena sanderana,
gypsophila and related plants.
Erwinia nimipressuralis
Wetwood
of elm,
slime flux, due to bacteria pathogenic in elm
trunk wood, especially Asiatic elms, but possibly
occurring in many other trees, including maple,
oak, mulberry, poplar, and willow. A water-
soaked dark discoloration of the heartwood is
correlated with chronic bleeding at crotches and
wounds and abnormally high sap pressure in
trunk, with wilting a secondary symptom. The
pressure in diseased trees increases from April
to August or September, reaching 5 to 30 pounds
per square inch (as much as 60 pounds in one
record). The bacteria inhabit ray cells mostly and
do not cause a general clogging of water-
conducting tissues. This pressure, caused by fer-
mentation of tissues by bacteria, causes fluxing,
a forcing of sap out of trunks through cracks,
branch crotches, and wounds. The flux flows
down the trunk, wetting large areas of bark and
drying to a grayish white incrustation. Bacteria
and yeasts working in the flux cause an offensive
odor that attracts insects.
Control
Bore drain holes through the wood
below the fluxing wound, slightly slanted to facil-
itate drainage. Install 1/2-inch copper pipe to
carry the dripping sap away from the trunk and
buttress roots. Screw the pipe in only far enough
to be firm; if it penetrates the water-soaked wood,
it interferes with drainage.
Erwinia rhapontica
Rhubarb Crown Rot
, sim-
ilar to soft rot.
Erwinia stewartii (see
Pantoea stewartii
).
Bac-
terial Wilt
of corn,
Stewart's Disease
on sweet
corn, sometimes field corn, in the middle regions
of
the United States,
from New York to
California.
Erwinia tracheiphila
Bacterial Wilt
of cucur-
bits,
Cucumber Wilt
on cucumber, pumpkin,
squash, and muskmelon but not watermelon.
The disease is generally east of the Rocky Moun-
tains and is also present in parts of the West; is
most serious north of Tennessee. Total loss of
vines is rare, but a 10 to 20 % loss is common.
This is a vascular wound disease transmitted
by striped and 12-spotted cucumber beetles. Dull
green flabby patches on leaves are followed by
sudden wilting and shriveling of foliage, and
drying of stems. Bacteria ooze from cut stems in
viscid masses. Partially resistant plants may be
dwarfed, with excessive blooming and
branching, wilting during the day but partially
recovering at night. The bacteria winter solely
in the digestive tract of the insects and are depos-
ited on leaves in spring with excrement, entering
through wounds or stomata.
Control
is directed chiefly at the insects. Start
vines under Hotkaps and spray or dust with rote-
none or other insecticide when the mechanical
