Dr.Banarsi Lal, Dr. Shahid Ahmad
Wheat is the major staple food in India and is a leading source of protein (13%) in human food. India is the second largest producer of wheat in the world after China. The wheat yield in India can be enhanced by minimizing the yield losses due to diseases. In recent years yellow rust of wheat has emerged as the major threat to the wheat crop. Efforts are needed to minimize the losses caused by the yellow rust of wheat and to develop the new varieties that can resist this disease. The stripe or yellow rust of wheat is the most important fungal disease in wheat crop. This disease affects the yield and quality of wheat crop. Yellow rust disease of wheat severely affects the entire Jammu regions viz. Reasi, Udhampur, Jammu, Kathua, Samba districts of J&K.KVKs of Jammu region are making strenuous efforts to manage this disease through awareness camps, farmers’ trainings, Kissan Gosthis, campaigns. Krishi Vigyan Kendras (KVKs) use electronic and print media to create more and more awareness on yellow rust of wheat. Severe infections can cause yield losses, mainly by reducing the number of kernels per spike, test weights and kernel quality.
Yellow rust of wheat is caused by the fungus namely Puccinia striiformis sp. tritici. Symptoms appear as small, bright yellow pustules (uredia) closely arranged in rows, parallel to veins appear on upper surface of leaves and leaf sheaths. The yellow pustules are also developed on heads including awns. The causal agent infects the green tissue of the wheat plant and the infection can take place at one leaf stage to a mature plant. The fungus usually forms long and narrow stripes, appearing as yellow to orange between veins and on leaf sheaths. This fungus is an excellent air traveller and can travel to long distances under favourable climatic conditions. Among the three rusts in wheat this fungus is the most damaging one in reducing the grain yield in wheat crop. The arrangements of pustules in stripe (resembling sewing machine stitches) are the prominent visual symptoms distinguishing it from other two rusts of wheat. On maturity, the pustules break- open, releasing a yellow orange mass of uredospores. In severe conditions, the serial arrangement seems to have lost due to over-crowded pustules. As the plant approaches maturity, dull black telia (bearing teliospores) often develop on lower surface of the leaves. The telia remains covered by the host epidermis as a black flat crust.
Wheat is the only known host of P.strifformis sp. tritici. Since, only uredospores and teliospores are known to occur, it seems to be hemiform rust. The pathogen perpetuates through uredispores on volunteer self sown wheat at high altitudes. In India, the pathogen survives in Himalayan foothills in J&K., Punjab, H.P. and western U.P from there; the uredospores are blown to comparatively lower altitudes and finally reach to plains in the month of December-January to cause primary infection. Of the three rusts of wheat it appears earliest in the Indian plains. Low night temperature and presence of dew are favourable for this disease. Under such conditions, new generations of uredpspores (repeating spores) can be produced at every 8-10 days causing fast secondary spread of the disease. If crop maturity is delayed due to extended winter, it is likely that the crop may face terminal severity of the rust. Yellow rust can be easily identified by rubbing fingers over the leaf blade and looking of yellowish powder. Yellow rust should not be confused with any discolouration on wheat leaves.
Management
The yellow rust of wheat is best managed by use of resistant varieties of wheat. Fortunately, good numbers of rust-resistant varieties are available for different agro- climatic zones. Variety resistance is the most economical method to control yellow rust of wheat. The farmers are adviced to spray the following 3 fungicides i) Tebuconazole 250EC (Folicur) @ 0.1% (1 ml/litre) ii) Propiconazole (Tilt) 25 EC @ 0.1 % (1 ml / litre)
iii) Triademefon (Bayleton 25WP) @ 0.1%. At the initial appearance of yellow rust one ml of chemical should be mixed in one litre water and thus 200 ml of fungicide mixed with 200 L of water should be sprayed in one acre wheat crop. If need, farmers are advised to repeat the spray. Spary should be done when weather is clear i. e. no rain, no fog / dew etc. It is recommended 2-3 sprays of Tilt (Propiconazole) at fortnightly intervals to protect the wheat crop from this disease which causes a severe loss to the wheat crop. In organic fields this disease can be protected by the spray of fermented butter milk. Mentha (pudina) leaf dust can also be used to control this disease. This disease appears in circles in the field. The farmers should apply the recommended doses of chemicals in the field to avoid this disease. Farmers should regularly visit their wheat fields so that disease infestation can be managed in the beginning. It is also advisable to refrain from monoculture of single variety as the chances of an individual variety to become prone to a specific strain is more than growing number of resistant varieties on different fields.
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