Powdery mildew of wheat is a fungal disease caused by the pathogen Blumeria graminis f. sp. tritici. It is a widespread disease that affects wheat crops worldwide, causing significant yield losses if left untreated.

The systematic position of pathogen

• Causal organism: Blumeria graminis f. sp. tritici (syn. Erysiphe graminis)
• Class: Ascomycetes
• Order: Erysiphales
• Family: Erysiphaceae

Distribution

The powdery mildew of wheat is commonly found in regions with enough moisture during showing time. This disease has no or little importance in the plains of India. This disease is commonly found in the lower hilly tracts of northern India.

Symptoms

The pathogen is an obligate parasite usually found on leaves, young shoots, inflorescences, and other young host plant tissues. The fungus may appear in an isolated white path in the beginning, which may merge with other patches and form big ones on the leaves. Sometimes whole of the leaf is found to be affected. The mycelium on the host is entirely superficial, forming a matted flocculent growth, at first white when the conidia are formed, then changing into a grey or reddish-brown color when cleistothecia are developed.

The leaves become crinkled, twisted, or deformed in severe cases. The top of the shoot droops down, and withers, and ear development is checked to some extent. Later on, at the earing time, small, dot-like, spherical cleistothecia are usually formed in the superficial mycelial weft. From much discoloration and coverage of the host epidermis by the fungus, photosynthesis is less, and there is much chlorosis, which weakens the plant. The development of the infected ears is arrested, and the ears wither. If the disease incidence takes place at the milk stage, the grains are dried and shriveled.

Nature & Recurrence of Powdery mildew of wheat

The disease’s recurrence occurs through the cleistothecia ( the perennating body). The cleistothecia perennate on the straw and plant debris after harvest and provide the necessary inoculum for the next season. Ascospores bring the primary infection, and the secondary infection is from the airborne conidia.

Management of Powdery mildew of wheat

• Resistant varieties: The best control method is to sow the resistant varieties. Much work has been done in the USA and Canada to evolve the resistant varieties.
• Chemical control: Sulpher dusting is effective in managing this disease. But the cost of treatment is prohibitive, and the control is not practical.