Home' Grower : November 2009 Contents The South Australian Grower -- November 2009
Pest and disease
Capsicums infected with the tobacco mosaic virus can be reduced in size and show mottling and
colour changes when ripening.
Capsicum virus threat
needs grower action
By TONY BURFIELD
SARDI Sustainable Systems -- Entomology
UnitSEVERAL growers have recently
sought assistance for unfamiliar
plant symptoms advancing
through their crops.
At first, the disease was thought to be
pepper mild mottle virus, but it has been
identified as a well-known virus in the
tobacco mosaic group that can occasionally
affect capsicums. It has caused significant
yield loss on several farms and the problem
The good news is that this disease has
only affected a few farms, is not new to
Australia and not spread by insects.
However, it can be easily spread by
humans and persists for a long time in crop
waste. It can also be seed borne.
The history of this disease in capsicums
in Virginia seems to have only involved
three or four farms during the past four
years, and neighbours' crops of the same
variety have not been infected.
This means, meaning commercial seed
is unlikely to have been the source of
The viruses are spread by mechanical
transmission or through old plant debris in
the soil which can re-infect new crops.
In greenhouses the closely packed plants
and frequent handling of the crop can lead
to a rapid spread of the virus once it is
introduced into the system.
The virus enters the plant through
microscopic leaf and stem wounds or
abrasions from contact with a
contaminated source like another infected
plant, plant waste, hands, tools and
clothing. Root damage from other diseases
may also provide a means of entry.
Leaves may become lighter in colour and
show some scarring, without becoming
Infected plants may not be noticed until
fruit symptoms are evident, raising the risk
of spread to other plants.
Infected fruit can be reduced in size
and show mottling and colour changes
In Virginia, growers are noticing
significant distortion in young and
developing fruit, with bubbly, rough skin
and some leaf yellowing.
There are no control methods once the
plant is infected, just like tomato spotted
Once an outbreak occurs, infected plants,
workers, tools and production areas must
be managed through total hygiene to avoid
Sick plants and their immediate
neighbours should be covered with a
plastic bag, pulled out and disposed of off
farm or underground.
Workers and visitors must maintain strict
contact hygiene at all times to avoid
spreading the disease across the crop or to
At the end of a crop all plants and crop
waste must be removed -- not ploughed in
-- to prevent the disease persisting in plant
debris in the soil and reinfecting the next
Support for growers can be obtained
through SARDI or the Horticulture
Australia Limited Integrated Viral Disease
A partnership program between SARDI
and the New South Wales Department of
Primary Industries, 'Keep it clean', can also
assist growers address persistent pest
problems and threats.
Details: Tony Burfield 0401 120 857,
Early symptoms difficult to notice
Disease remains in crop waste
Farm hygiene critical
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