Black or stem rust of wheat
Causative agent: Puccinia graminis f.sp. Tritici.
Symptoms:
- Uredial pustules(or sori) are oval to spindle shaped and dark reddish brown (rust) in color.
- Uredinials with urediniophore rupture epidermis of leaf, leaf sheath and stem with in one to two week new infection begins releasing spore to initiate the next generation of infection.
- Pycnia appear on upper leaf surface of barberry plant. Generally they are small cluster and release pycnidiospore in sticky honey dew. After 5-10 days later, cup shaped structure filled with orange yellow and powdery aeciospore break from bottom surface leaf.
Etiology:
- teliospores are two celled and thick walled.
- The uredospores are brown, oval shaped, thick walled and marked with thin short spines and borne singly on stalks.
Favorable environment:
- High relative humidity
- Tempr 25C
Survive and spread:
- Heterocious life cycle : complete life cycle in two host.
- Survive: teliospore present on stem of wheat,basidiospore present on alternate host like barbery and mahonia.
- Spread: uredinispore are major spread conidia through wind.
Management:
- Eradication of self-sown wheat plants weed hosts, alternate host.
- Adjust time of sowing.
- Grow resistant varieties like Kalyanasona, Sonalika, Choti Lerma, Lerma Rojo, Safed lerma, NP 700 & 800.
- Avoid late sowing ¾ Balanced application of nitrogenous fertilizers.
- Seed dressing with Plantavax@0.1% followed by two sprays with the same chemical.
- Spray twice or thrice with Zineb@0.25% or Mancozeb@0.25% or Plantavax@0.1% , at 15 days interval.
- Fungicide like azoxystrobin at 200g/l + cyproconazole at 80g/l, tebuconazole + tridimenol and tebuconazole were most effective in reducing stem rust. Epoxiconazole at 125 g/l + carbendazium at 125 g/l were reduction of the disease.
- Potassium carbonate at all concentration ,sodium bicarbonate at 15 ad 20 g/l ,potassium bicarbonate at 10,15 and 20 g/l and ammonium at10,15 and 20 g/l, dipotassium bicarbonate at 20g/l inhibit spore germination by 95-100%. Kcl and Nacl at 10, 15 and 20g/l also inhibit the germination (Azmeraw, Admassu, Abeyo, & Bacha, 2020).