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 />
Management<br />
Bacterial wilt cannot be controlled with fungicides, and bactericides are seldom<br />
available to farmers and generally very expensive. Management principles for<br />
bacterial wilt are as follows:<br />
• Remove sources of disease from the field by:<br />
o Planting <strong>potatoes</strong> in soils free from bacterial wilt.<br />
o Using healthy seed not infected with bacterial wilt.<br />
o Rotating potato crops with other non-solanaceous crops. Good practice is to<br />
rotate <strong>potatoes</strong> with corn or sweetpotato. In fields with serious infections, it is<br />
best to plant non-host plants for more than 2 years, as agents of bacterial wilt<br />
can survive in the ground without host for that amount of time.<br />
o Removing infected plant debris before planting and clearing weeds away<br />
before planting, while plants are growing and at harvesting time.<br />
o Using composted <strong>org</strong>anic fertilizer not infected with bacterial wilt.<br />
o On heavily infested soils, apply brassica residue based biofumigants.<br />
• Inhibit the development and spread of bacterial wilt in the field by:<br />
o Putting dolomitic lime on the soil around infected plants as this increases soil<br />
pH, creating a less favorable environment for the pathogen..<br />
o Carefully managing irrigation in the field by digging channels that allow water to<br />
flow freely from the field. Bacterial wilt will spread rapidly in flooded fields. Also<br />
when watering the field, try to make sure water does not flow over the surface<br />
of the field.<br />
o Using water not contaminated with bacterial wilt to irrigate the crop.<br />
o Cleaning the field by destroying (burning or burying) plants and tubers infected<br />
with bacterial wilt throughout the whole season.<br />
o Cleaning farming tools after use.<br />
Observation methodology<br />
You can begin making field observations for bacterial wilt at 35 DAP by looking at<br />
symptoms on affected plants. Identifying an infection as bacterial wilt can be done by<br />
using the following methods:<br />
• Testing plants with vascular flow test – This will determine whether plants with<br />
symptoms of wilting are infected by bacterial (and not fungal) wilt. Cut 2-3 cm<br />
lengths off stems at the base of plants showing signs of infection. Suspend these<br />
pieces vertically in water and leave for a while. If the plant is infected with bacterial<br />
wilt, milky threads of bacterial ooze will flow from the stem pieces into the water.<br />
• Testing tubers – Cut a sample tuber near its base, leave it for a few minutes, or<br />
squeeze it. If it is infected with bacterial wilt, it will exude a thick white fluid.<br />
• Testing soil with bioassay test – Three-week old tomato seedlings grown on BWfree<br />
substrate and several soil samples suspected of infection are used for testing.<br />
Put the soil samples in pots and water them with clean water. Plant five tomato<br />
seedlings in each pot, and tend them for one or two months. Make observations<br />
by looking at symptoms that appear on each of the plants in the pots. When wilting<br />
appears, test the plants with vascular flow tests. Wilting plants that exude a milky<br />
flow in the vascular flow test are proof that their pots contain infected soil. You can<br />
also do this test to determine if manure contains bacterial wilt.<br />
10.1.2 Blackleg or soft rot<br />
Blackleg or soft rot is a widespread disease caused by the bacterium Erwinia spp.,<br />
which affects stems and tubers particularly in warm and humid regions.<br />
60<br />
ALL ABOUT POTATOES