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Ministry of Agriculture, Food and Rural Affairs


Gray fly about half the size of a house fly

Is this disease...?


That’s Right!


This is a picture of iris yellow spot virus. In seed onions and onions grown from transplants the lesions are irregular and can easily be mistaken for botrytis leaf blight. In onion sets or garlic, symptoms are more easily identified by yellow lesions surrounding an area of green tissue. Iris yellow spot virus is a disease vectored and trasmitted by onion thrips. It is often observed at the end of July into August. Botrytis leaf blight is a fungal disease that is weather dependant and occurs from June on. Another diagnostic is that lesions caused by Botrytis often have a halo around the lesion, there aren't any halos associated with iris yellow spot virus.

Iris yellow spot virus Botrytis leaf blight

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