Biology Reference
In-Depth Information
Rolstonia solanacearum (formerly
Pseudomo-
nas solanacearum
).
Southern Bacterial Wilt
, also
called
Brown Rot
,
Bacterial Ring Disease
,
Slime
Disease
,
Granville Wilt
(of tobacco), present in
many states but particularly prevalent in the South,
from Maryland around the coast to Texas. South-
ern wilt is common on potatoes in Florida but also
appears on many other vegetables - bean, lima
bean, castor bean, soybean, velvet bean, beet, car-
rot, cowpea, peanut, sweet potato, tomato, egg-
plant, pepper, and rhubarb. Ornamentals
sometimes infected include ageratum, anthurium,
dwarf banana, garden balsam, geranium, canna,
cosmos, croton, chrysanthemum, dahlia, holly-
hock, lead-tree, marigold, nasturtium, Spanish
needle, sunflower, and zinnia. The symptoms are
those of a vascular disease, with dwarfing or sud-
den wilting, a brown stain in vascular bundles, and
dark patches or streaks in stems. Often the first
symptom is a slight wilting of leaves at end of
branches in the heat of the day, followed by recov-
ery at night, but each day the wilting is more
pronounced and recovery less until the plant dies.
Young plants are more susceptible than older ones.
In potatoes and tomatoes there may be a brown
mushy decay of stems, with bacterial ooze present.
Potato tubers often have a browning of vascular
ring, followed by general decay.
Bacteria live in fallow soil 6 years or more and
may persist indefinitely in the presence of sus-
ceptible plants. They are spread by irrigation
water, in crop debris, or soil fragments on tools
and tractors, or by farm animals. Optimum tem-
peratures are high, ranging from 77
to 97
F,
with inhibition of disease below 55
F.
Control
Use northern-grown seed potatoes and
Sebago and Katahdin varieties, more resistant
than Triumph and Cobbler. Use a long rotation
for tomatoes. Soil can be acidified with sulfur to
kill bacteria, followed by liming in the fall before
planting.
Ralstonia solanacearum, Race 3, Biovar 2.
Bacterial wilting
of geranium; also yellowing and
stunting.
Xanthomonas albilineans
Leaf Scald
of sugar-
cane (FL, TX).
Xanthomonas axonopodis
Leaf Streak
(water
soaking) of African lily and
Leaf Blight
of onion.
Xanthomonas begoniae (see
Xanthomonas
campestris
pv.
begoniae
).
Begonia Bacteriosis
,
leaf spot of fibrous and tuberous begonias.
Xanthomonas campestris
Black Rot
of
cruciers,
Bacterial Blight
,
Wilt
,
Stump Rot
of
alder, arabidopsis, asparagus tree fern, avocado,
cabbage, cauliflower, broccoli, brussels sprouts,
kale, lavender, mustard, radish, rutabaga, sun-
flower, stock, turnip, and leaf blight of onion.
Black rot was first observed in Kentucky and
Wisconsin about 1890 and is generally distrib-
uted in the country, with losses often 40 to 50 %
of the total crop. It is one of the most serious
crucifer diseases, present each season but epi-
demic in warm, wet seasons.
The bacteria invade leaves through water
pores or wounds and progress to the vascular
system. Veins are blackened, with leaf tissue
browning in a V-shape. With early infection
plants either die or are dwarfed, with a one-
sided growth. Late infection results in defolia-
tion, long bare stalks with a tuft of leaves on
top. When stems are cut across, they show
a black ring, result of the vascular invasion, and
sometimes yellow bacterial ooze. Black rot is
a hard odorless rot, but it may be followed by
soft, odorous decays. Primary infection comes
from bacteria carried on seed, or in refuse in
soil, but drainage water, rain, farm implements,
and animals aid in secondary infection.
Control
Use seed grown in disease-free areas in
the West or treat with hot water, 122
F, 25 min
for cabbage, 18 min for broccoli, cauliflower, and
collards. Plan a 3-year rotation with plants other
than crucifers, and clean up all crop refuse.
Xanthomonas campestris
Horse-Radish Leaf
Spot
. Leaves are spotted but there is no vascular
infection. Also causes leaf spot of
Pilea
sp.,
Pellionia
sp. and leaf spot and blight of bird of
paradise, white butterfly. Also, bacterial leaf and
stem lesions.
Xanthomonas
Small rods, motile with a single polar flagellum;
form abundant slimy yellow growth. Most spe-
cies are plant pathogens causing necroses.
