Biology Reference
In-Depth Information
Xanthomonas campestris
Bacterial Leaf Spot
on cabbage and radish.
Xanthomonas campestris pv. asclepiadis -
Bacterial Blight
on butterfly weed.
Xanthomonas campestris pv. barbareae
Black
Rot
of winter-cress (
Barbarea vulgaris
), similar
to black rot of cabbage; small greenish spots turn
black.
Xanthomonas campestris pv. begoniae (for-
merly
Xanthomonas begoniae
).
Begonia
Bacteriosis
, leaf spot of fibrous and tuberous
begonias. Blister-like, roundish dead spots are
scattered over surface of leaves. Spots are
brown with yellow translucent margins. Leaves
fall prematurely, and in severe cases the main
stem is invaded, with gradual softening of all
tissues and death of plants. Bacteria remain via-
ble at least 3 months in yellow ooze on surface of
dried leaves. Leaves are infected through upper
surfaces during watering, with rapid spread of
disease when plants are crowded together under
conditions of high humidity.
Control
Keep top of leaves dry, avoiding syring-
ing or overhead watering; keep pots widely
spaced; spray with bordeaux mixture and dip
cuttings in it.
Xanthomonas campestris pv. carotae (for-
merly
Xanthomonas carotae
).
Bacterial Blight
of carrot. The chief damage is to flower heads
grown for seed, which may be entirely killed.
Symptoms include irregular dead spots on leaves,
dark brown lines on petioles and stems, blighting
of floral parts, which may be one-sided. Use clean
seed, or treat with hot water; rotate crops.
Xanthomonas campestris pv. citri
Citrus Can-
ker
on all citrus fruits, but not apparently eradi-
cated from the United States. It came from the
Orient and appeared in Texas in 1910, becoming
of major importance in Florida and the Gulf
States by 1914, ranking with chestnut blight and
white pine blister rust as a national calamity. But
here is one of the few cases on record where man
has won the fight, where a disease has been nearly
eradicated by spending enough money and hav-
ing enough cooperation early in the game. Sev-
eral million dollars, together with concerted
intelligent effort by growers, quarantine mea-
sures, destruction of every infected tree, sanitary
precautions so rigid they included walking the
mules through disinfestant, sterilization of
clothes worn by workers - ill saved us from
untold later losses.
Symptoms of citrus canker are rough, brown
corky eruptions on both sides of leaves and fruit.
On foliage the lesions are surrounded by oily or
yellow halos. Old lesions become brown and
corky.
Xanthomonas campestris pv. corylina (for-
merly
Xanthomonas corylina
).
Filbert Blight
,
Bacteriosis
, the most serious disease of filberts
in the Pacific Northwest, known since 1913 from
the Cascade Mountains west in Oregon
and Washington. The disease is similar to walnut
blight (see
X. juglandis
) with infection on
buds, leaves, and stems of current growth; on
branches; and on trunks 1 to 4 years old. The
bacteria are weakly pathogenic to the nuts.
Copper-lime dusts are effective, with four to six
weekly applications,
starting at
the
early
prebloom stage.
Xanthomonas campestris pv. cucurbitae (for-
merly
Xanthomonas cucurbitae
).
Bacterial Spot
on winter squash and pumpkin. Leaf spots are
first small and round, then angular between
veins, with bright yellow halos; sometimes trans-
lucent and thin but not dropping out; often coa-
lescing to involve whole leaf. Bacterial exudate is
present.
Xanthomonas campestris pv. cyamopsidis
Rot
of
Lithops
spp.
Xanthomonas campestris pv. dieffenba-
chiae
Blight
of
Anthurium
; also
Leaf Spot
of
cocoyam.
Xanthomonas campestris pv. dieffenbachiae
(formerly
Xanthomonas dieffenbachiae
).
Dief-
fenbachia Leaf Spot
. Spots are formed on all
parts of leaf blade except midrib, but not on
petioles and stems. They range from minute,
translucent specks to lesions 3/8 inch in diameter,
circular to elongated, yellow to orange-yellow
with a dull green center. Spots may grow together
to cover large areas, which turn yellow, wilt, and
dry. Dead leaves are dull tan to light brown, thin
and tough but not brittle. The exudate on lower
surface of spots dries to a waxy, silver-white
layer.
