Biology Reference
In-Depth Information
Control Separate infected from healthy plants;
keep temperature low; avoid syringing; try pro-
tective spraying with streptomycin.
Xanthomonas campestris pv.
fragariae Angular Leaf Spot on strawberry;
also Blossom Blight on strawberry.
Xanthomonas campestris pv. glycines (for-
merly Xanthomonas glycines ( phaseoli var.
sojense ). Bacterial Pustule of soybean, similar
to regular bean blight but chiefly a foliage dis-
ease, present in most soybean areas, more severe
in the South. Small, yellow-green spots with red-
dish brown centers appear on upper surface of
leaves with a small raised pustule at the center of
the spot on the under leaf surface. Spots run
together to large irregular brown areas, portions
of which drop out, giving a ragged appearance.
Bacteria overwinter in diseased leaves and on
seed. Variety CNS is highly resistant; Ogden has
some resistance.
Xanthomonas campestris pv. gummisudans
(formerly Xanthomonas gummisudans ). Bacterial
Blight of Gladiolus. Narrow, horizontal, water-
soaked, dark green spots turn into brown squares
or rectangles between veins, covering entire leaf,
particularly a young leaf, or middle section of the
blade. Bacteria ooze out in slender, twisted, white
columns or in a gummy film, in which soil and
insects get stuck. Disease is spread by planting
infected corms or by bacteria splashed in rain
from infected to healthy leaves. The small dark
brown corm lesions are almost unnoticeable.
Soak corms unhusked for 2 h before planting.
Xanthomonas campestris pv. hederae (for-
merly Xanthomonas hederae ). Bacterial Leaf
Spot of English ivy. Small water-soaked area on
leaves develop dark brown to black centers as
they increase in size, sometimes cracking, with
reddish purple margins. Spots are sometimes
formed on petioles and stems, with plants
dwarfed and foliage yellow-green. Spray with
bordeaux mixture or an antibiotic. Keep plants
well spaced; avoid overhead watering and high
humidity.
Xanthomonas campestris pv. hyacinthi (for-
merly Xanthomonas hyacinthi ). Hyacinth Yel-
lows , yellow rot of Dutch hyacinth, occasionally
entering
The disease was first noted in Holland in 1881
and named for the yellow slime or bacterial ooze
seen when a bulb is cut. The bulbs rot either
before or after planting, producing no plants
above ground or badly infected specimens,
which do not flower and have yellow to brown
stripes on leaves or flower stalks. Bacteria are
transmitted by wind, rain, tools, and clothes,
with rapid infection in wet or humid weather,
particularly among luxuriantly growing plants.
The disease is usually minor in our Pacific North-
west but worse in warm, wet weather on rapidly
growing plants. Innocence is more susceptible
than King of the Blues.
Control Cover infected plants with a jar or can
until the end of the season; then dig after the
others. Never work or walk in fields when plants
are wet; avoid bruising; discard rotten bulbs;
rotate plantings; avoid fertilizer high in nitrogen.
Xanthomonas campestris pv. incanae (for-
merly Xanthomonas incanae ). Bacterial Blight
of garden stocks causing, since 1933, serious
losses on flower-seed ranches in California; also
present in home gardens. This is a vascular dis-
ease of main stem and lateral branches, often
extending into leaf petioles and seed peduncles.
Seedlings suddenly wilt when 2 to 4 inches high,
with stem tissues yellowish, soft and mushy, and
sometimes a yellow exudate along stem. On older
plants, dark water-soaked areas appear around
leaf scars near ground, stem is girdled, and
lower leaves turn yellow and drop; or entire
plants wilt or are broken by wind at ground
level. Bacteria persist in soil and on or in seed;
they are also spread in irrigation water.
Control Use a 2 to 3-year rotation. Treat seed
with hot water, 127.5 to 131 F for 10 min,
followed by rapid cooling.
Xanthomonas campestris pv. juglandis -
formerly Xanthomonas juglandis ). Walnut Blight
on English or Persian walnut, black walnut, but-
ternut, Siebold walnut. Black, dead spots appear
on young nuts, green shoots, and leaves. Many
nuts fall prematurely, but others reach full size
with husk, shell, and kernel more or less black-
ened and destroyed. Bacteria winter in old nuts
or in buds, and may be carried by the walnut
erinose mite.
the
country
in
imported
bulbs.
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