Submitted by Vinod Kumar on
Wheat Crops Rusts Disease and their management
Rusts are caused by three different species of the fungi, Puccinia. Brown and yellow rusts are particularly important in the north-western India. Black rust appears quite late in these areas and normally do not cause substantial damage except in wheat fields sown very late. However, black rust appears in severe form in southern, central and eastern India and cause significant damage.
- Leaf Rust./Brown-Rust: The small, round-oval spots (called pustules) of brown rust (caused by Puccinia recondita tritici) develop mainly on the leaves but under severe attack, appear on sheath and stem as well. Bright orange spots appear either in small clusters or irregularly scattered spreads very fast on susceptible varieties during warm and humid environmental conditions. In case of severe attack, plants mature early with poor root development and produce light and shriveled grains. This rust is most widespread in the country and generally the most damaging in many areas.
- Stripe Rust /Yellow Rust: This rust is caused by the fungus, Puccinia strciformis. Yellow spots develop mainly on the leaves, but in case of severe attack, spots can also appear on leaf sheaths, stalks and glumes. The spots are oval in shape and lemon-yellow in colour and are formed in long streaks or rows, and smaller than those of brown rust. Appearance of lemon-yellow pustules in rows is characteristic feature of yellow rust. Under severe attack, these rows are not distinct, and large part of the plant gets covered with crowded pustules. Yellow rust is predominant in hills, foot-hills and north-western part of the country where the temperatures are low. In plains it does not cause much damage.
- Stem Rust. /Black Rust: Black rust of wheat is caused by Puccinia graminis tritici. The spots occur on stem, leaf sheath, leaves and ear-heads but the stem is often most severely affected. The spots are reddish-brown in colour and elongated in shape. It spreads fast under relatively warmer and humid climate. As the crop matures, dark, black, elongated spots are formed. Black rust, though prevalent all over the country, appears in epidemic forms in the southern, central and eastern India, which are characterized by high temperatures in the wheat growing season.
Management of rusts -Most effective method for control of rust, is to grow rust-resistant varieties. Biodiversity among wheat cultivars can also effectively check the rust problem. Use 3-4 wheat varieties at a time on each farm. Avoid late sowing or late maturing varieties. To protect the crop from rust infection, spray 5 liters of sour buttermilk mixed with 200 liter of water. Amaranth (chaulai or lal bhaji – a common green leaf vegetable) or Mentha (Pudina) leaf dust can also be used as fine spray (25- 30 gm dry leaf powder per lit of water) to prevent the infection of rusts. Foliar spray of dry leaf extract of Hibiscus rosa-sinensis (China rose) can also prevent the rust infection.