Biology Reference
In-Depth Information
pea, pepper, celery and other vegetables. Orna-
mentals include amaryllis, aster, begonia,
blackberry-lily, calendula, calla, chrysanthe-
mum, dahlia, delphinium, fuchsia, gaillardia,
gloxinia, nasturtium, geranium, primrose, petu-
nia, Rieger begonia, hydrangea, stephanotis,
salvia, stock, verbena and zinnia.
In tomato there are bronze, ringlike secondary
lesions; plants are stunted with some necrosis;
there may be a yellowish mosaic with leaf distor-
tion. Fruits are often marked with concentric
rings of pale red, yellow, or white. Potatoes
have zonate necrotic spots on upper leaves,
streaks on stems, which collapse at the top; plants
are stunted, with small yield. Lettuce is yellowed,
with retarded growth, brown blemishes on central
leaves; affected spots are like parchment but with
brown margins. Peas have purplish necrotic spots
on stems and leaves following mottling, and cir-
cular spots and wavy lines on pods. Spots on
outer stalks of celery are first yellow, then
necrotic with pockets of dead tissue inside peti-
oles; plants are stunted and worthless.
China asters have dead tan areas in leaves,
brown surface blotches on stems. Calla lillies
have whitish, then brown spots and streaks. On
sweet pea, reddish brown to purple streaks may
run full length of the stem. Circular to oval leaf
spots with diffuse margins are followed by
yellowing and death of leaves and stems. Blos-
soms sometimes develop a circular pattern in the
pigment. Delphiniums may have numerous dis-
tinct double rings. The viruses causing oak leaf
and ring spot in dahlia are probably strains of the
spotted wilt virus.
Transmission is by onion and flower thrips.
Only the larvae can become viruliferous by feed-
ing on infected plants, but then there is an incu-
bation period of 5 to 9 days, during which the
insect becomes adult, before the virus can be
transmitted to healthy plants.
Tomato Infectious Chlorosis
Closterovirus
Transmitted by white fly - Trialeurodes
vaporariorum ; caused interveinal yellowing and
necrosis in infected tomato plants.
Tomato Mosaic Tobamovirus
Circular, water-soaked necrotic spots on leaves;
black streaks on veins; concentric sunken rings
on fruit.
Tomato Pseudo Curly Top
Hybrigeminivirus
Spreads among tomato plants in Florida. Virus is
transmitted by treehopper Micrutalis malleifer .
Virion genome consists of circular ssDNA.
Tomato Ring Spot Nepovirus
Curling and extensive necrosis of shoot termi-
nals; brown rings and streaks on leaflets, stems,
fruits, more pronounced at high temperature.
Causes leaf streaks in iris, crumbly fruit of red
raspberry and chlorotic spot of geranium. May
infect chicory, healall, black medic, moth mul-
lein, impatiens, apple, common cinquefoil and
dandelion. Transmission is by dagger nematodes.
Plants that may serve as reservoir plants for
Tomato Ringspot Virus are: chickweed, henbit,
dandelion, woodsorrel, plantain,
strawberry,
sorrel and red clover.
Tomato Spotted Wilt Tospovirus
More serious on the Pacific Coast, but also occur-
ring in Florida, Texas and some central and east-
ern states in greenhouses and sometimes outdoors
on plants such as ragwort, purslane, nightshade,
desert-rose, and puncture vine. Spotted wilt is
common on tomato, potato,
Tomato Streak; Double Streak
Caused by Tobacco Mosaic Tobamovirus plus
Potato X Potexvirus. Leaves are mottled green
with numerous small, grayish brown papery
tobacco,
lettuce,
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