Plant diseases in India and their control.

The concept of development is reviewed in terms of sustainability. Food production in India driven by pressure from an increasing human population uses 90,000 t per year of technical-grade pesticide: 12% of this is fungicide and a good part is insecticide for the control of vectors of plant viruses. A change in the cropping pattern and irrigation have provided a summer 'green bridge' along Tamil Nadu/Andhra Pradesh border areas for the tungro virus that affects rice and its vector. Epidemics occur along the coramandal coast, if the weather is suitable. Red rot disease of sugarcane is promoted by poor drainage, river widening, ratooning, contaminated planting material and variation in the pathogen throughout the Indo-Gangetic plain. Apple production uses large amounts of fungicide. For every 1000 t of apples produced 1t of fungicide is sprayed 8-10 times sequentially. Systemic application of fungicides has led to pesticide resistance and resurgence of other diseases. 70-80% of the Nagpur Mandrin produce reaches the market by trucks that have to traverse 1000 km. 10.6% of fruits are lost to post-harvest diseases; culling, sunburn and injuries account for another 11.6%. In the control of leaf rust of wheat in North India, the use of varietal mosaics, resistance genes and extra-late wheat sowings that do not coincide with favourable weather have all collectively contributed to loss reduction. The drop in the production of exportable crops such as peppers and coconuts because of diseases needs attention. The traditional wisdom on crop mixtures, organic manuring, shifting sowings, etc, needs scientific re-evaluation.