Management
of the disease due to some races is by adopting 2-3 years crop rotation. On the
contrary wilt caused by the heterogeneous solanaceous race 1, which is most
prevalent through out the Indian sub-continent, is really difficult to manage.
Avoidance by using healthy seed: The pathogen perpetuates through two distinct ways viz. infected tubers and field soil. Latently infected but looking healthy tubers are the most important carriers of R. solanacearum. High load of inoculum is carried in vascular tissues, on surface and in lenticels and not eradicated by low temperatures in the long period of cold storage. Such infections go unnoticed. Carry over of the pathogen in seed tubers has played very significant role in disease epidemics and its local, continental and intercontinental spread. Therefore introduction of inoculum in the field can be best avoided by use of healthy seeds. Wilt can also be effectively managed by use of healthy seeds in infested soils. Use of healthy seeds alone for planting in infested soil reduces wilt incidence by 44 to 94 %.
Avoidance of congenial conditions for disease development. In North-eastern and North-western hills, wilt does not appear in summer crop before July. Therefore planting potato crop in second week of February and harvested in June reduces wilt incidence to a negligible extent.
Field
inoculum can be brought down considerably by physical and chemical manipulations
and soil amendments.
Exclusion
by physical and chemical means: Raising
the soil temperature to 85 °C
for 15 minutes by steam application effectively eliminated the pathogen from the
soil up to the depth of 30-40cm. Thus wilt incidence was negligible
where Jhum
cultivation is a common practice eg. in north-eastern regions of India.
Raising the soil temperature by covering the field with polythene film has been
found to be effective in reducing the wilt.
Soil disturbance has deleterious effect on survival of the pathogens. One to two deep ploughings of the field during summer in plains and winter ploughing in hills reduces the wilt incidence to an extent of 70%. These ploughings expose the infected root remnants, plant debris, and bacteria glued in soil in the form of pellets to desiccating sunshine.
Use of soil disinfectants and broad-spectrum toxic chemicals such as chloropicrin, DD mixture, ethylene di-bromide, sulphur followed by lime and zinophos have been found to check the disease. Application of bleaching powder @ 12 kg/ha mixed with fertilizer or soil drenching before or after first earthing up reduced the bacterial wilt incidence by 80% and also increased potato yield.
Soil
amendments also help in wilt management. It is a popular perception that acidic
or alkaline soil is not conducive to the bacterial wilt pathogen.
Exclusion by means of crop rotations: Planting non-host rotational crops also brings down incidence of bacterial wilt. It helps in exclusion of the pathogen by way of starving, increasing antagonist activity and reducing multiplication of the pathogen. Successful reduction in wilt incidence has been obtained by following crop rotations with wheat, maize, oat, barley, sun hemp, finger millet and vegetables like cabbage, onion, garlic and others. Among the above rotational crops, roots of finger millet remains free from R. solanacearum. However, all other plants carried root infection as small necrotic lesions without systemic colonisation. Therefore, these crops can help reducing the pathogen buildup without completely eradicating it.