Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
serious proportion during 2008-2009 in different districts of Sindh and Punjab. Farmers in Sindh
were celebrating the spring festival in March 2009 anticipating a rich wheat harvest from their
fields due to ideal environmental conditions. But after the harvest, the situation for many changed
and their happiness turned into gloom when they found that the yield was contrary to their
expectations. The yield reduced from 6.0 tons/ha to a mere yield of 1.6 to 2.2 tons/ha from their
potential lands.
Several bacterial diseases are well established in seed stocks. Few examples are:
bacterial blight in rice (Xanthomonas oryzae); common bacterial blight of bean (X. phaseoli ); black
rot of crucifers (X. campestris pv. campestris); and Black arm in cotton (X. malvacearum); These
diseases caused major menace to the respective crop production.
Bacterial blight of paddy was 1st observed in Mahrashtra (formerly Bombay) State in 1951,
when it was reported in Kolaba District but it was not until 1963 that an outbreak of disease
occurred accounting for total crop failure as happened in Punjab, Haryana and Western Uttar
Pradesh States of India in 1979 and 1980. In India, the disease has accounted for more than 20%
rice crop loss, periodically. Most Seed borne viruses are asymptomatic and transmit efficiently
through infected seed and further disseminated by a number of vectors. The losses are attributed
to the environmental conditions and the prevalence of the vector population in that area. For
example, one infected plant will produce 100% infected seed (soybean mosaic virus) such seed
will be viable and germinate well, but the resulting plants will be infected and yields will be
significantly reduced. All these examples exemplify the significance of seed borne pathogens and
their effect on seed production.
New Challenges
With the new dimensions in Indian agriculture, which is not only confined to the varietal
developments by conventional breeding for crop improvement in yield and quality traits but for
value addition and for food biosecurity, new tools are being used for crop improvement,
(transgenics, or BT crops) by way of biotechnology. This may change the scenario of the
pathogens and plant diseases in agriculture. Thus, a threat form exotic destructive pests is
foremost importance in the era of liberalized import under WTO. However, the changing conditions
the indigenous pests already existing but having the lower damage level in India are changing their
habit and gaining importance over the years.
Resurgence of seed-borne diseases: cropping system
With the change in cropping system there is resurgence of diseases. Examples are
necrosis in sunflower and ground nut that can not be neglected for crop production and food
security. Apart from the threat posed by resurgence, a large number of diseases are endemic and
continue to cause losses in given area ,example is Karnal Bunt of Wheat.
Resurgence of seed-borne diseases: Chemical pesticides
With the excessive use of chemical pesticides, number of resistant strains of pests have
evolved which are the constant threat and need improved measures for disease management
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