CSU Coop Extension Pest Alert Bulletin - Vol. The disease is associated with severe growth reduction and dieback of the crown in areas east of the Great Plains.
Green ash are more tolerant of the disease whereas white ash are killed.
A survey of green ash to detect the ash yellows casual agent was conducted in 1996 and 1997 throughout Colorado, North and South Dakota, Nebraska, Kansas, Wyoming, Manitoba, and Saskatchewan. Fifteen sites representing urban landscapes, wind breaks, and natural plantings were sampled in each state or province. Ten to fifteen trees were sampled at each site and small roots collected and assayed by immunofluorescence with a monoclonal antibody specific for the ash yellows phytoplasma. Ash yellows phytoplasma was present at every site sampled in each state and province. We were surprised to find some trees in all areas of the state that we surveyed to have the phytoplasma.