Biology Reference
In-Depth Information
Xanthomonas pelargonii (see Xanthomonas
campestris pv. pelargonii ). Bacterial Leaf Spot
of geranium ( Pelargonium ).
Xanthomonas pelargonii (see Xanthomonas
campestris pv. pelargonii ). Geranium Leaf Spot
on Pelargonium spp.
Xanthomonas phaseoli (see Xanthomonas
campestris pv. phaseoli ). Bacterial Bean Blight ,
general and serious on beans but rare in some
western states.
Xanthomonas pruni (see Xanthomonas
campestris pv. pruni . Bacterial Spot of stone
fruit, also called canker, shot hole, black spot;
general on plum, Japanese plum prune, peach,
and nectarine east of the Rocky Mountains.
Xanthomonas vesicatoria (see Xanthomonas
campestris pv. vesicatoria . Bacterial Spot of
tomato and pepper, common in wet seasons.
Xanthomonas vesicatoria var. raphani (see
Xanthomonas campestris pv. raphani ). Leaf
Spot of radish, turnip, and other crucifers, similar
to bacterial spot on tomato.
Xanthomonas vignicola (see Xanthomonas
campestris pv. vignicola ). Cowpea Canker on
cowpeas and red kidney beans.
Xanthomonas vitians (see Xanthomonas
campestris pv. vitians ). Bacterial Wilt and Leaf
Spot of lettuce, South Carolina Lettuce Disease ,
wilting and rotting of lettuce leaves and stems.
Xanthomonas nigromaculans (see
Xanthomonas campestris pv. zinniae ). Leaf Spot
on zinnia.
Xylella fastidiosa Bacterial Leaf Scorch on
maple, pecan, mulberry, northern red oak and
sweet gum.
Pierce's Grape Disease First described as Cal-
ifornia vine disease by Pierce in 1892, now
known as cause of grape degeneration in Gulf
states; reported from Rhode Island. First symp-
toms are scalding and browning of leaf tissues,
often with veins remaining green; canes die back
from tips in late summer; growth is dwarfed, fruit
shriveled; roots die. The bacterium invades the
xylem and turns it brown. Alfalfa plants are
stunted with short stems and small leaves. Many
species of sharpshooter leafhoppers transmit the
bacterium to grape from alfalfa, clovers, grasses,
also from ivy, acacia, fuchsia, rosemary, zinnia,
and other ornamentals that are symptomless car-
riers. There is no adequate control; roguing of
diseased vines and spraying for leafhoppers has
proved ineffective. Propagate by cuttings from
disease-free vineyards.
Mycoplasmataceae
Phytoplasma
Ash Yellows and Witches' Broom On ash in
Michigan, Montana, Nebraska, North Carolina,
and South Dakota and peanut in Oklahoma.
Aster Yellows Throughout the United States,
also called Lettuce Rio Grande Disease, Lettuce
White Heart, Potato Purple Top.
Bean Phyllody Perhaps caused by a strain of
aster-yellows MLO.
California Aster Yellows In the West, also
known as Celery Yellows, Western.
Aster Yellows, Potato Late Break, Strawberry
Green Petal. Aster yellows may appear in more
than 170 species of 38 families of dicotyledons.
It is serious on China aster, may also affect
anemone, calendula, coreopsis, cosmos, purple
coneflower (Echinacea), delphinium, daisies,
golden-glow, hydrangea, marigold, petunia,
phlox, scabiosa, strawflower, and other flowers.
It is serious on lettuce, alfalfa, endive, carrot,
parsley, New Zealand spinach, radish, and some
other vegetables, but not on peas, beans, or other
legumes. This disease is now known to be caused
by a phytoplasma organism.
In most plants vein clearing is followed by
chlorosis of newly formed tissues, adventitious
growth, erect habit, virescence of flowers. Asters
have a stiff yellow growth with many secondary
shoots; are stunted, with short internodes; flowers
are greenish, dwarfed, or none. The chief vector
is the six-spotted leafhopper ( Macrosteles
fascifrons ). The virus multiplies in the insect,
and there is a delay of 10 days or more after the
insect feeds on a diseased plant before it can
infect a healthy specimen. There is no transmis-
sion through insect eggs or aster seeds.
Celery petioles are upright, somewhat elon-
gated, with inner petioles
short, chlorotic,
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