Symptoms of witches’ broom disease are manifest as dense clusters of short, flexible, thornless branches with stunted leaves, and branch dieback ...

Although viral causality has not been demonstrated, the first discovery of an emaravirus-like genome in symptomatic blue palo verde trees heavily infested by the previously suspected eriophyid mite vector [Aculus cercidi (Keifer et al. 1982), which "reached high population densities in symptomatic palo verde trees" but was hard to find in asymptomatic trees], and the absence of virus-mite complexes in asymptomatic trees, provide a robust association of an emaravirus with witches’ broom disease of blue palo verde, herein proposed as blue palo verde broom virus.

- M. Ilyas, S. Avelar, U. K. Schuch, and J. K. Brown: (2018) First Report of an Emaravirus Associated with Witches’ Broom Disease and Eriophyid Mite Infestations of the Blue Palo Verde Tree in Arizona^©