All about potatoes.pdf - Vegetableipmasia.org

10.
MAJOR POTATO DISEASES
Viral diseases have developed from one generation to the next primarily due to
farmers’ habit of basing their seed potato selection on the size of the potatoes alone.
Generally, viral diseases lead to smaller potato tubers being produced.
Consequently, when tubers are sorted and selected for seed, the majority of seed
potatoes chosen are those already infected with viral diseases.
A key factor when obtaining seed from your own field is selecting healthy plants for
parent stock.
Despite variations, management principles are nearly the same for all viral diseases.
Viruses can be controlled by:
• Using virus free seed: It is very risky to select seed potatoes based on size alone,
as plants infected with viral diseases generally produce smaller tubers. Strict
sorting and selection is highly recommended when a part of the harvest will be
used for seed.
• Destroying plants infected with viral diseases: Plants displaying symptoms of viral
diseases must be pulled up, collected and destroyed. Viruses can spread from
one plant to another through vectors, so removing infected plants will also remove
the source of disease for other plants.
• Controlling insects that can spread viral diseases: Generally, sucking insects such
as aphids, thrips, mites and whiteflies can spread viruses. Therefore,
management of these insects can reduce the spread of viral diseases.
• Using plant resistant varieties: This can only be done if available in sufficient
quantities.
• Not using pesticides: Viruses cannot be controlled by any form of pesticide.
10.3.1 Leafroll virus
Potato leafroll virus (PLRV) is an important disease in potato plants, and can cause
reduced yields of up to 90%.
Symptoms
Leaves curl upward and turn pale yellow. If you press them they feel brittle and
fragile. In advanced infections, plant growth becomes stunted, leaf stems stand
upright, leaves curl, tighten and turn pale green. Severe infections cause potato
plants to produce tiny tubers, or prevent them from producing any tubers at all.
Source and Vector
PLRV can be introduced into a potato field by infected seed tubers or by aphids who
act as vector spreading the disease from one field to another.
Observation methodology
Symptoms appear during the early stages of potato growth, so observations should
begin at that time. Make observations by walking along the raised seedbeds and
looking for plants showing symptoms of the disease.
10.3.2 Potato Y virus
Potato Y virus (PVY) is the second most important virus. It can be passed on through
infected tubers or by insects and can reduce yield by up to 80%.
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ALL ABOUT POTATOES