Alan
McNab
Professor of Plant Pathology |
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Viruses that may occur
on peppers include i) tobacco mosaic (TMV), ii) potato virus
X (PVX), iii) cucumber mosiac (CMV), iv) tobacco etch (TEV),
v) potato virus Y (PVY), and vi) alfalfa mosaic (AMV). Symptoms
vary, depending on the virus or strain, the plant, time of year,
and environmental conditions. The range of virus symptoms may
include leaf mottling, puckering, or curling; stem and petiole
streaking; rough, deformed, or spotted fruit; stunted plants;
and blossom and fruit drop.
Cucumber Mosaic Virus
Tobacco Mosaic Virus
Potato Virus X
Tobacco Etch Virus
Potato Virus Y
Alfalfa Mosaic Virus
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Viruses:
Cucumber Mosaic Virus (CMV) causes severe mosaic on pepper
foliage; older leaves somtimes exhibit large dead rings. Fruit
may be malformed, and conspicuous yellow concentric rings and/or
spots are frequently observed on infected green fruit. Limited
spread may occur in the field through handling plants. By far
the most efficient and widespread vector is the green peach
aphid; other aphids also may spread CMV. The virus overwinters
in susceptable perennial plants such as catnip, chickweed,
jimson weed, mallow, nightshade, pokeweed, wild lettuce, and
others. CMV may persist in a very small percentage of seed
from infected chickweed. |
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Tobacco
Mosaic Virus (TMV), on some pepper cultivars, causes very pronounced
mosaic symptoms on the foliage, accompanied by leaf puckering
and reduction in leaf size. Vein clearing of the young leaves
becomes extremely pronounced. OPlder leaves fall prematurely.
Yieldis reduced because fewer fruit set and those that do set
are small and misshapen. Many bell-shaped peppers are resistant
to TMV. TMV commonly is transmitted by mechanical means--during
handling, on tools, through infected debris in soil, and by seeds.
TMV, the most persistant and highly infections of all plant firuses,
withstands head and retains its infective capacity in a dry condition
for many years. |
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Potato
Virus X (PVX) causes a mild mosaic symptom with mild leaf puckering.
Leaf size may be slightly reduced. The virus is spread by contact
between diseased and healthy plants, during handling, and by
chewing insects. PVX carries over in infected potato tubers;
it can infect many different kinds of plants belonging to the
potato-tomato family. |
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Tobacco
Etch Virus (TEV) causes a very mild chlorotic mottle, with some
foliar distortion. Large concentric rings and line patternsmay
be produced on leaves and on fruit. Fruit often becomes misshapen.
Root necrosis occurs, causing some wilting. Wilted plants recover,
but usually are stunted and bushy. Stems on old plants sometimes
have reddish brown spots and are streaked. Bud drop may occur.
TEV overwinters in weeds belonging to the potato-tomato family
and is spread mostly by green peach aphids and occasionally by
potato aphids. |
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Potato Virus Y (PVY) causes mild
to severe mottling, depending on the particular virus strain
involved. The virus is not seed-transmitted, but is spread by
several aphid species; the green peach aphid probably is the
most efficient vector. |
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Peppers: Viruses: Alfalfa
Mosaic Virus (AMV) symptoms depend on the virus strain and the environmental
conditions under which the crop grows. Yellow blotches or sometimes
mosaic mottling, yellowish rings, spots, and other patterns appear
on infected leaves. Severe leaf death also may occur. AMV overwinters
in alfalfa plants; it is transmitted most commonly by the green
peach aphid. |
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