Amelioration of Purple Blotch Disease in Onion (Allium cepa L.) Seedlings with Organic Soil Amendments

Abstract

Pot experiments with transplanted onion seedlings were evaluated for management of purple blotch disease. Sets of 100,150 and 200g of poultry droppings, cattle dung, neem leaves, rice husk and a mixture of rice husk and poultry droppings (1:1) were incorporated per kilogram of soil. Spore suspension of Alternaria porri (5x105) was also applied to the rhizosphere of the onion seedlings. Common symptoms of purple blotch (elliptical purple lesions, wilting and defoliation) were assessed. Poultry dropping amendment was most effective; reducing lesions to 15± 3.6% from 85± 2.6%, wilting reduced to 20± 4.0% from 70± 3.0% and defoliation to zero from 60± 3.5%. The amendments, especially at the concentration of 150 and 200g/kg soil reduced symptoms severity compared to control. Onion farming should be complemented with application of degradable organic materials, especally poultry droppings and cattle dung, to reduce the incidence and severity of purple blotch disease.