Mechanically Transmitted Tobamovirus
Found worldwide
Symptoms
Foliar symptoms of pepper mild mottle mosaic virus
(PMMV) consist of mottling and yellow/green mosaic,
while fruit may be small, malformed and mottled, with
sunken or raised necrotic spots. Yield loss is
considerable when young plants become infected.
Conditions for Disease Development
PMMV is not transmitted by insects. It can be seedborne,
consequently, the seedlings can be infected by
mechanical contamination from their seed coats during
transplanting or other cultural procedures. This is a
primary source of infection.
The virus is quite stable and highly infectious and is
easily spread from plant to plant during normal crop
maintenance. Also, the virus can persist in the previous
crop in infected pepper debris such as leaves, stems
or roots in soil for several months.
Control
Resistance to PMMV is available in some varieties.
Consult with your extension agent for recommendations.
Use seed from healthy plants. If seed is suspected
of infection with PMMV then do the following: soak
seeds in 10% trisodium phosphate (TSP) for 2.5 hr while
stirring the seeds in the solution. Change the TSP once
after 30 min. Rinse seeds thoroughly in tap water after
the treatment to remove residues of TSP and spread
seeds out to dry. The above procedure will significantly
reduce levels of PMMV in external and internal portions
of the pepper seed. Do not re-contaminate seed by
placing them in used containers.
Use a 1-year rotation to avoid continuous pepper
cultivation. Keep production area and seedbeds free of
volunteer peppers that can serve as over-wintering hosts
for the virus.
If growing seedlings and transplants in a
greenhouse, then use steam-pasteurized soil in which
plant debris has been allowed to thoroughly decompose
since PMMV may be protected in thick pieces of root
and stem refuse.
Avoid touching or handling pepper plants prior to
setting them in the field. Remove diseased pepper
seedlings that show mild mottle or mosaic symptoms
on the foliage. Remove one or two plants adjacent to
those plants that show symptoms. Do not touch other
seedlings while discarding them. Dip hands in milk while
handling plants every 5 minutes (more often if different
lots of plants are handled). Rubber gloves will protect
hands. Do not clip or damage young seedlings since
this increases the possibility of mechanical transmission
of the virus from contaminated tools or hands.
Remove diseased plants from the field as soon as
virus symptoms are noticed. This will reduce the spread
of the virus by direct contact between plants. Work in
diseased portions of fields last, after working in healthy
portions of fields. Cultural practices should be used
that minimize contact with plants by workers and
equipment or tools.
Disinfect tools, stakes, and equipment before moving
from diseased areas to healthy areas. This can be done
by: 1) soaking 10 minutes in a 1:10 dilution of a 5.25%
sodium hypochlorite, do not rinse; or 2) by washing
(enough to clean) in detergent at the concentrations
recommended for washing clothes or dishes. Keep all
solutions fresh.
Hands and tools may be washed with soap or milk.
Work in diseased areas after working in unaffected parts
of a field. Wash clothing that comes into contact with
ToMV/TMV-infected plants with hot water and a
detergent.
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