Field library

Stemphylium Blight

A fungus disease of the leaves. It begins as small yellow or light brown spots, usually on the side of the leaf facing the wind, and the spots then join up, turn dark brown to black and look sooty. The leaf dries off from the tip downward and dies early. When the leaves die before time the bulb stays small and the crop weighs much less at harvest.

How to scout

Go into the field early in the morning while the leaves are still wet with dew, and turn over the middle and older leaves of ten or fifteen plants, looking for small pale spots with a darker centre and for leaf tips that are drying back.