Management of Turnip
Mosaic Virus (TuMV) in Cabbages
Turnip
Mosaic Virus
symptoms on cabbage leaves
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Order/Family:
Potyviridae:
Potyvirus
Type:
disease
(viral)
Common
names:
cabbage
A virus mosaic / Cabbage black-ringspot virus
Host
plants:
Cabbage/Kale,
Brassicas Crucifers (Black mustard, cauliflower, broccoli,
radish) / Beets / Tobacco
|
General Information on Disease and Damage
Geographical
distribution
 |
|
Geographical
Distribution of the Turnip Mosaic Virus in Africa (shaded
areas)
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Damage
Infected plants are
stunted, with leaves coarsely mottled and distorted. Black spots
develop on leaves which prematurely drop. Early infection of cabbage
by this virus in the seedbed or soon after transplanting
can reduce yield by 75%, whereas late-season infection has little or
no effect on yield. It also reduces seed yield.
Host range
Turnip mosaic virus
(TuMV) has a very wide host range infecting at least 318 species in
156 genera of 43 families. TuMV infects most cruciferous plants, but
is most damaging in Chinese cabbage, turnip, mustard, and radish. It
also attacks beets, spinach and tobacco.
Symptoms
On cabbage: Mosaic,
black speckling or stippling of cabbage heads at harvest or during
storage can be caused by the TuMV or the cauliflower mosaic virus
occurring singly or together. The latter causes lumpy or warty
growths on the veins on the under surface of leaves and vein
clearing. In stored cabbage, black sunken spots develop on leaves
throughout the head. The spots are considerably larger than those
caused by cauliflower mosaic virus. Its mode of transmission is
similar to TuMV (i.e. aphids and mechanically). However, cauliflower
mosaic virus has a restricted host range. It is infectious only to
members of the cabbage family (brassicas).
Affected plant
stages
Flowering stage,
fruiting stage, seedling stage and vegetative growing stage.
Affected plant
parts
Leaves, seeds, stems
and whole plant.
Symptoms
by affected plant part
Leaves:
lesions; abnormal colours; abnormal patterns; abnormal forms;
yellowed or dead. Seeds:
empty grains; lesions. Stems:
external discolouration; abnormal growth; dieback. Whole
plant:
plant dead; dieback; dwarfing; early senescence.
Biology and Ecology of the Turnip Mosaic Virus
Transmission
TuMV is transmitted
by
aphids notably
green peach aphid (Myzus
pericae)
and cabbage aphid (Brevicoryne
brassicae)
and is readily transmitted mechanically. The virus is transmitted by
aphids in a non-persistent manner (short virus transmission period of
10 to 30 seconds) with no latent period (the time from start of an
acquisition feeding until the vector can infect healthy plants with
the virus). It can be acquired in less than one minute and can be
inoculated in less than a minute. The transfer of viruses by aphids
usually occurs over short distances (up to a few hundred metres),
particularly down-wind and involves migrating alates (winged aphids).
Weather conditions and temperature influence aphid activity and
migration patterns which in turn affect dissemination of TuMV. Dry
and warm conditions favour aphid reproduction and dissemination and
hence early and increased spread of the virus. Cool, wet and windy
conditions reduce the reproduction and movement of aphids and hence
spread of the virus. Once primary infections are established in
fields, TuMV may spread relatively rapidly from plant to plant if
aphids are not controlled. Seed transmission of the virus has not
been observed.
Sources of
Infection
Primary sources of
TuMV infection are diseased host plants and weeds. Vectors can be
introduced into field crops with infected transplants. Transplants
can become infected during propagation in nursery beds. It is not
seed transmitted.
Pest and disease management:
Cultural
practices
Control of Turnip
Mosaic Virus is quite difficult due to the very wide host range of
the virus, the ineffectiveness of insecticides in controlling the
spread of non-persistently
transmitted viruses, and the lack of immune crop cultivars.
Control options
Locate seedbeds away
from weedy fields. Weeds and volunteer plants should be eliminated
from seedbed areas and preferably from production fields. It may be
helpful to discard plants from outside rows in seedbeds.
Hygiene
A very common method
of transferring the virus from plant to plant is on contaminated
hands and tools. When transplanting
seedlings, wash your hands frequently and thoroughly with soap and
water. Field equipment should be used in new fields first and then in
older fields. Never attempt to transplant a healthy plant into the
soil from which a diseased plant was removed. Roots from diseased
plants will remain in the soil and provide the virus source for the
new transplant. Field sanitation, particularly, weed control is very
important since the virus can infect many weed species.
Resistant
cultivars
In areas where
Turnip Mosaic Virus is serious and endemic,
growing of Danish cabbage varieties should be considered. These
varieties have been reported to have some resistance
to TuMV (Sherf and Macnab, 1986)
Information Source Links
- Dobson H., Cooper J., Manyangarirwa W., Karuma J., and Chiimba W. (2002). Integrated Vegetable Pest Management. Natural Resources Institute (UK). ISBN: 0-85954-536-9
- OISAT: Organisation for Non-Chemical Pest Management in the Tropics. www.oisat.org
- Sherf, A.F. and Macnab, A.A. (1986). Vegetable Diseases and Their Control. John Wiley & Sons, Inc. ISBN: 0 471 05860 2
- Varela, A.M., Seif, A.A., and Löhr, B. (2003). A Guide to IPM in Brassicas Production in Eastern and Southern Africa. ICIPE, Nairobi, Kenya. ISBN: 92 9064 148 7 www.icipe.org
