It is considered to be the oldest known disease. It is the potential cause of economic loss in all wheat growing areas. It is of three types:
i)Black Stem Rust
Causative agent of this disease is Puccinia graminis tritici.This problem is high in the hills and mountains where local varities are cultivated. Due to the use of improved varities in Terai, this disease is not seen. Pustules are found on stem elongated and long brownish to black coloured. It may appear on leaves under severe condition.
ii) Brown Leaf Rust
This disease is caused by fungus Puccinia recondite. Pustules are brown in colour and scattered all over the leaves. Pustules are spherical rarely seen on leaves.
iii)Yellow Striped Rust
Causative agent of this disease is Puccinia striiformis. Pustules are yellow in color confined along in between veins. Pustules are elongated appear in linear fashion. It may also appear on leaf sheath in severe codition.
- Use resistant varieties like WK1204, Pasang Lhamu
- Use fungicides like Dithane M45 75% WP at the rate of 1.5-2 kg in 750 litres of water per hectare
- Short duration varieties of wheat should be recommended
- Cultivating susceptible varieties of wheat in high hills and resistant varieties in mid hills helps in controlling disease in main fields of Terai
This is seen particularly in those areas where local varieties are cultivated. So this is serious in hilly areas. Causative agent of this disease is Ustilago tritici .The infected plants are slightly taller than healthy plants and develop chlorotic leaves. All the spikelets of affected pants are transformed into black powdery mass of spores. There is no grain formation. Before emergence, the smutted spikelets are covered by a thin membrane which is silvery but it breaks while emerging out the earheads. These are loosely attached and can be blown up easily.
- Seed treatment with systemic fungicides like vitavax at the rate of 2gm per kg is effective
- Solar Heat Treatment: Seeds are soaked in cold water for 4-6 hrs, dormant mycelium becomes active and seeds are spread on cemented floor on direct sunlight for 4-6 hrs
- Hot water treatment at 550C for 10-15 mins.
- Development and use of resistant varieties
LEAF BLOTCH OR TANSPOT:
It is very common disease found throughout the Terai, Inner Terai, as well as in Hills. There is involvement of 2-3 pathogens in this disease namely Pyrenophora tritici-repentis, Bipolaris sorokiniana, Alternaria triticina. Spots appear as tan brown flecks which expand into the lens shaped and have yellowish halo around the spots. These tan blotches expand upto few mm long often with chlorotic or yellow borders. Such leisons may coalesce and become more dark brown in color.
- Development and use of resistant varieties: Chinese variety ‘Chiria’ is used for crossing to transfer resistant gene to other variety
- Chemicals like Tilt, Horizon can be used to spray. Just 2 spray can control the disease upto 95%.
- Early planting can escape severity of infection and Use of short duration varieties