Biology Reference
In-Depth Information
Disinfest tools, grader, digger, and bags; sweep
storage house clean and spray with copper sul-
fate, 1 pound to 5 gallons of water.
Clavibacter xyli
Rhodococcus fascians (formerly
Clavibacter
fascians
).
Fasciation
, widespread on sweet pea,
also on carnation, chrysanthemum, gypsophila,
geranium, petunia, impatiens,
Hebe
sp. and pyre-
thrum. Sweet pea symptoms are masses of short,
thick, and aborted stems with misshapen leaves
developing near the soil line at first or second
stem nodes. The fasciated growth on old plants
may have a diameter of 3 inches but does not
extend more than an inch or two above ground.
The portion exposed to light develops normal
green color. Plants are not killed, but stems are
dwarfed and blossom production is curtailed.
Control
Sterilize soil or use fresh.
Rickettsialike bacteria
Bacterial Wilt
on
Toronto creeping bentgrass; bacteria found in
xylem of roots, crown, and leaves. Initially, leaf
blades wilt from tip down and within several days
entire leaf wilts, becomes dark green, shriveled,
and twisted; also leaf scorch of mulberry.
subsp.
cynodontis
Stunting
Disease
of bermudagrass.
Clavibacter xyli
subsp. xyli
Ratoon Stunt
of
sugarcane.
Corynebacterium agropyri (formerly
Clavibacter agropyri
).
Yellow Gum Disease
on
western wheat grass. Enormous masses of surface
bacteria form yellow slime between stem and
upper sheath and glumes of flower head; plants
dwarfed or bent; normal seeds rare.
Corynebacterium
humiferum formerly
Clavibacter
humiferum
).
Reported
from
wetwood of poplar, in Colorado.
Curtobacterium flaccumfaciens pv.
flaccumfaciens (formerly
Clavibacter
flaccumfaciens
).
Bacterial Wilt of Bean
, wide-
spread on kidney and lima beans and soybean,
causing considerable loss. Plants wilt at any stage
from seedling to pod-production, with leaves
turning dry, brown, and ragged after rains. Plants
are often stunted. Bacteria winter on or in seed,
which appear yellow or wrinkled and varnished.
When infected seed is planted, bacteria pass from
cotyledons into stems and xylem vessels. Other
plants are infected by mechanical injury and per-
haps by insects, but there is not much danger from
splashed rain. Plants girdled at nodes may break
over.
Control
Use seed grown in Idaho or California.
Curtobacterium flaccumfaciens pv. poinset-
tia (formerly
Clavibacter poinsettiae
).
Stem
Canker
and
Leaf Spot
of Poinsettia, a relatively
new disease, first noted in greenhouses in 1941.
Longitudinal water-soaked streaks appear on one
side of green stems, sometimes continuing through
leaf petioles to cause spotting or blotching of
leaves and complete defoliation. The cortex of
stems turns yellow, the vascular system brown.
Stems may crack open and bend down, with glis-
tening, golden brown masses of bacteria oozing
from stem ruptures and leaf lesions.
Control
Discard diseased stock plants; place
cuttings from healthy mother plants in sterilized
media; avoid overhead watering and syringing;
rogue suspicious plants promptly.
Enterobacteriaceae
Erwinia
Motile rods (usually) with peritrichous flagella;
Gram-negative; producing acid with or without
visible gas from a variety of sugars; invading
tissues of living plants producing dry necroses,
galls, wilts, and soft rots. The genus is named for
Erwin F. Smith, pioneer in plant diseases caused
by bacteria.
Enterobacter cloacae
Bulb Decay
on onion.
Erwinia amylovora
Fire Blight
, general on
many species in several tribes of the Rosaceae,
particularly serious on apple, pear, and quince.
Other hosts include almond, amelanchier, apri-
cot, aronia, blackberry, cherry, chokecherry,
cotoneaster, crabapple, exochorda, geum, haw-
thorn, holodiscus, India hawthorn, kerria, Japa-
nese quince, loquat, medlar, mountain-ash, plum,
photinia, pyracantha, raspberry, rose, spirea, and
strawberry.
Apparently a native disease, first noticed near
the Hudson River in 1780, fire blight spread south
and west with increased cultivation of pears and
apples. By 1880 it had practically wrecked pear
