Witch and stunt Deformed leaves and canes can have many causes, including herbicide injury, witches broom, gall wasps, blueberry stunt disease and viruses . A rust fungus called witches' broom causes unusual growth. The alternate host for this fungus is white fir. Blueberry stem gall wasps cause swellings on canes. Severe stunting could be caused by a mycoplasm called blueberry stunt .
Leaves are small and tend to be cupped downwards.
The organism is transmitted by the sharp-nosed leafhopper. First of 5 instars of sharp-nosed leafhopper. To control spread of stunt, the leafhoppers must be controlled.