Significance

• The ash flower gall mite, known as an Eriophyid gall mite, begins to feed on male ash trees in the spring before their buds begin to fully bloom. These microscopic mites are able to squeeze into the flower structure before it appears fully open to the human eye. They produce green galls that eventually tun brown and begin to stand out in August and September. The ash flower gall can remain hidden on the tree for as long as two years.
  
  

Building the Gall

• The ash flower gall mite (Eriophyes fraxinivorus) overwinters beneath flower buds and begins feeding and laying eggs in the early spring. No more than 1/50 inch in size, the mite stimulates the new flower to form a mutated growth of tissue -- the gall -- that becomes both a protective shelter and a feeding center for the mite. The first symptoms of gall growth display as round, green globs about 1 inch in size that form on the flowers.
  
  

Damage

• At least two generations of ash flower gall mites occur each season. Aside from some loss of aesthetic value, the galls and mites do little harm to the tree. In extreme cases, the weight of larger galls may cause branches and twigs to droop. While this may be of concern to homeowners and gardeners, the galls may also be considered to be a unique and interesting touch to the tree and landscape, especially as the design and color of a gall is specific to each species of gall mite.
  
  

Management

• The fact that the gall mite moves into the flower before it begins to open makes control extremely difficult. In addition, since this process occurs in early April, most gardeners have yet to begin thinking about or practicing pest management. Some control of the ash flower gall mite is feasible if the buds are sprayed with dormant oil approximately one week before they begin to bloom.