Background
Pepino (Solanum muicatum) is an edible fruit known
as pear melon, a South American crop. In 1974, a mosaic virus, called
pepino mosaic (PepMV) was detected in Peru. This virus was of little concern
until it was discovered outside of South America in 1999, not on pepino,
but on greenhouse tomatoes in the Netherlands. Since then, this virus
has spread to greenhouse tomato production facilities in the UK, France,
Spain, and Germany. PepMv was first reported in Canada and the United
States in July of 2001. Colorado appears to be an area where this disease
is present. According to a report in Plant Disease by French, et.al.,
tomato fruits originating from the United States were collected during
border inspections by the Canadian Food Inspection Agency and tested for
PepMv by ELISA antisera. Samples testing positive, were from Colorado,
Arizona, and Texas.
An extensive research program was initiated in the Netherlands to try
and understand this virus, including what its' risk potential is and possible
management strategies. Some experts from the European Community (EC) have
suggested that this disease be placed on the EPPO (European and Mediterranean
Plant Protection Organization) Alert list. The purpose of this list is
to draw the attention of EPPO member countries to certain pests that may
present a risk to them and to offer an early warning for new plant pests.
This is NOT a Quarantine List, however, there is discussion going on about
what measures need to be taken for trade of plant material and phytosanitation.
What is known about PepMV
Damage
The virus appears to spread rapidly, and can cause significant crop losses,
if not detected early. Growers have reported losses ranging from 5% -
16%.
Transmission/Spread
PepMV belongs to the potexviruses, a group of viruses that are usually
transmitted by mechanical means. PepMV appears to be very contagious,
spread easily by contaminated tools, shoes, clothing, hands and plant-to-plant
contact. It has been reported that crop workers can transmit the virus
simply by brushing against affected plants. The virus is thought to remain
viable (able to cause infection) in dry plant material for as long as
3 months. Clothing worn in an infected crop is reported to remain infectious
for at least 14 days.
Bumbleblees have been associated with the spread of PepMV, however, the
risk of spreading the virus appears to be much greater by hand pollination.
The virus can also be transmitted by grafting or taking cuttings from
mother plants. Several possibilities exist for spread of the virus over
long distances, these include sap in fruits and contaminated seed material.
It doesn't appear that the virus is seed-borne, rather its possible that
the virus may be a contaminant on seeds.
Symptoms
Symptoms are variable and more commonly seen in the fall and winter months.
They include:
- Yellow mottled leaves, with "bubbles" that are a slightly
darker green color.
- Stunting , distortion or curling of the growing point, resembling
hormonal herbicide damage.
- Bright yellow spots or patches on leaves.
- Brown spots on older leaves or leaves close to the growing point.
- Brown corky streaks on stems.
- On fruit: red spots on orange fruits. More severe on large fruit varieties.
Browning of flowering sets and stem close to growing
point.
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Bright yellow patches on fully expanded leaves.
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Stunted growth of "head" or growing point
of tomato plant.
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Browning and abortion of flowers.
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Management
Prevention:
- Prevent the introduction of this disease by using disease-free seed
and plant material.
- Disinfest seeds before planting
- Keep all entry doors locked.
- Allow only necessary visitors by appointment.
- Wash hands with warm water and soap before and after visiting the
greenhouse.
- A foot-bath (filled with a solution of potassium hydroxide or sodium
hydroxide) located at the entrance of the greenhouse must be used by
all persons upon entering and exiting.
- All workers and visitors must use coveralls, plastic shoes or boots
and gloves.
- Don't wear bracelets, rings, or other jewelry when working with the
crop.
- Wash coveralls every week in hot water (203F/95C).
- Conduct work routine in only one direction.
- Disinfect recirculating water by using heat, UV or ozone.
- Dip tools and gloved hands in undiluted skim milk or virucidal disinfectatant
between every plant. The skim milk should contain at least 3.5% protein,
and as soon as the milk starts to sour, or curdles replace with fresh
milk.
- Remove all plant debris. Do not leave trash piles in, or near the
greenhouse.
- Check the crop regularly.
- Mark suspicious plants and check development every day.
Control
- Stop all work on rows where an infection is suspected, unitl the
cause is verified by testing.
- Remove infected plants. Preferably the whole row should be removed.
At the least remove 20 plants on either side of diseased plants.
- Make sure there is no contact between infected plants and healthy
plants.
- If replanting, use new slabs, drippers and plastic items.
- Do not share carts, crates, boxes, etc. with other operations.
- Powerwash, clean, and disinfect all carts and crates at the end of
each day.
Based on the information at hand this does appear to be a disease to
take quite seriously. It is most important to prevent the introduction
of this contagious virus into the greenhouse. Only through strict hygiene
at all stages during crop production and thorough cleanup procedures between
crops can the spread of this disease be minimized.
References:
De Ruiter Seeds - Holland. LTO Groeiservice Bulletin, Jan. 2000
http://www.deruiterusa.com/pepino.htm
Ferguson, G. 'Management of Pepino Moaic Virus in Greenhouse Tomatoes'.
Ministry of Agriculture, Food and Rural Affairs. Ontario, Canada. http://www.gov.on.ca/OMAFRA/english/crops/facts/01-017.htm.
French, C.J., Bouthillier, M. Bernardy M., Ferguson, G, Sabourin, M.,
Johnson, R.C., Masters, C., Godkin, S. and Mumford, R. 'First Report of
Pepino Mosaic Virus in Canada and the United States. Plant Dis. 85:1121
Jagers op Akkerhuis, F. and Stijger, I. 'Pepino Mosaic Virus, A New Disease
in Greenhouse Tomatoes' in Practical Hydopronics & Greenhouses, May/June
2001.
Laura
Pottorff
Regional Greenhouse Crops Specialist
CSU
Cooperative Extension - Adams County
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