Iris Yellow Spot Virus(IYSV) disease : Infected flower stalk
Pathogen: Tomato Spotted Wilt Virus (Tospo virus group)
Symptoms
First appear as straw-coloured, dry, tan, spindle or diamond-shaped lesions, with or without distinct green centers with yellow or tan borders on leaves. The symptoms are more pronounced on flower stalks. Infected leaves and stalks lodge during the latter part of the growing season.
Disease development
Onion thrips (Thrips tabaci) transmit IYSV in a persistent manner. Disease severity is positively correlated with thrips populations in the field. This virus is not seed transmitted. Over-wintering onions, volunteers from prior productions, infected transplants and alternate hosts can all serve as sources of both vector and virus.
Disease management
The disease is transmitted by thrips (Thrips tabaci) which is a major pest of onion. Uproot the virus infected plants and destroy by burning. The insect vector can be control by spraying of insecticides Fipronil 5 % SC @ 0.15 %, Deltamethrin 2.8 % EC @ 0.1 % before flowering and spinosad 2.5 % SC @ 0.1 % or neem oil @ 0.4 % and Beauveria bassiana @ 0.4 % in onion seed crop.
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