Iris Yellow Spot Virus(IYSV) disease : Green island tissue appearance
Pathogen : Tomato Spotted Wilt Virus (Tospo virus group)
Symptoms
Green islands of tissue can appear within a necrotic IYSV lesion. These types of lesions are less frequent than the tan, completely necrotic, lesions.
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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