Iris Yellow Spot Virus(IYSV) disease : Necrotic diamond-shaped lesion on leaves
Pathogen: Tomato Spotted Wilt Virus (Tospo virus group)
Symptoms
Appearance of necrotic diamond-shaped lesion. These lesions can be small to very large. Larger lesions are not obviously diamond-shaped but tend to be longer, along the length of the leaf, than wider.
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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