SCI-TECH & AGRI

Management of downy mildew in sunflower



Sunflower crop is among the top five commercial oilseed crops grown all over India.

Its cultivation is mainly hindered by diseases and pests. Among the diseases downy mildew is a serious obstacle in sunflower cultivation due to its systemic nature of infection.

Typical symptoms occur in seedling stage. Infested seedlings die, but those that survive produce stunted plants with erect, platform heads with no flowers.

Drought stress

If any flowers are produced they remain sterile and bear no seeds. The infested plants serve to perpetuate the fungus in the soil and are more prone to drought stress and lodging.

The disease is initiated by soil borne dormant structures called oospores or infected seeds.

Oospores germinate during spring in wet soils. They can survive in the soil for five to 10 years.

Cool, water-saturated soil during this period greatly favours the infection spread.

Plants become increasingly resistant to infection with age, so systemic infections occurs over a short period (two to three weeks) after germination.

Irrigation water running through an infested field also may carry mildew spores into a previously disease-free field.

Management

— Plant high quality certified seeds free from downy mildew pathogen.

— Practise a five-year or longer crop rotation between sunflower crops with non-hosts such as corn and small grains.

— Eliminate weeds that can serve as alternate hosts of downy mildew.

— Avoid reuse of irrigation water from sunflower fields and provide adequate but not excessive irrigation, especially early in the season.

— Seed treatment with metalaxyl 6gm/kg seed will reduce the infection during the seedling stage. Spraying of rydomil MZ 3gm/lit or metalaxyl 3gm/lit water helps in controlling foliar infection.

— Using resistant varieties. is a good practice.

Mallikarjun Y, Kenganal, Hemavati, Ranebennur & Byadgi, A. S.

Department of Plant Pathology

University of Agricultural Sciences,

Dharwad, Karnataka



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