All about potatoes.pdf - Vegetableipmasia.org
All about potatoes.pdf - Vegetableipmasia.org
All about potatoes.pdf - Vegetableipmasia.org
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10.<br />
MAJOR POTATO DISEASES<br />
Symptoms<br />
Leaf surfaces become uneven and brittle, leaves shrink and their ribs turn yellow. In<br />
mild infections, plants often show no signs of disease at all.<br />
Source and Vector<br />
Although the virus can spread with infected seed tubers and mechanical transmission<br />
through tools and plant/tuber handling, PVY is mostly transmitted by aphids who act<br />
as vector spreading the disease from one field to another. Aphids can acquire the<br />
virus within seconds after starting to feed on infected leaves, can transmit the virus<br />
immediately, in a non-persistent manner and usually retain the virus for only several<br />
hours without continued feeding on infected leave material.<br />
Observation methodology<br />
These are the same as for leafroll virus.<br />
10.3.3 Mosaic virus<br />
Symptoms<br />
Yellowy-green stripes appear on leaves infected by the Potato Mosaic Virus (PVM).<br />
Yield can diminish by up to 40%. In mild infections, affected plants display no<br />
symptoms.<br />
Source and Vector<br />
Like other viruses, PVM is caused by using contaminated seed, can be mechanically<br />
transmitted through tools and plant/tuber handling or is carried from other plants by<br />
aphids.<br />
Observation methodology<br />
These are the same as for leafroll virus.<br />
10.4 Diseases caused by nematodes<br />
10.4.1 Root-knot nematode<br />
Root-knot nematodes damage the parts of plants found under the ground, i.e. roots<br />
and tubers. Although this disease is found in many potato producing regions, farmers<br />
do not consider it too economically damaging and consequently pay it little attention.<br />
Nevertheless, these nematodes can reduce tuber quality and can make them more<br />
vulnerable to other diseases. Lesions caused by nematodes facilitate secondary<br />
infections by other diseases in the soil such as tuber rot and scab to get in.<br />
Symptoms<br />
Diseases caused by nematodes vary, but common symptoms of these are:<br />
• Swelling of roots – Nematodes damage and live in the roots of potato plants,<br />
causing them to swell. Swollen roots cannot function normally and affect growth of<br />
the plant above them. In hot conditions, plants damaged by nematodes will wilt.<br />
• Irregular tuber shape – Tubers change shape and lumps appear on their surfaces.<br />
Source and spread<br />
Sources of these diseases are soil and contaminated seed. Nematodes can move<br />
around in the soil with the help of water.<br />
A HANDBOOK TO THE ECOLOGY AND INTEGRATED MANAGEMENT OF POTATO 69