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Arboriculture & Urban Forestry Online
Volume 44, Issue 3 — May 2018

Drippy Blight, a Disease of Red Oaks in Colorado, U.S., Produced from the Combined Effect of the Scale Insect Allokermes galliformis and the Bacterium Lonsdalea quercina subsp. quercina

Rachael A. Sitz, Marcelo M. Zerillo, Jacob Snelling, Jorge Ibarra Caballero, Kathleen Alexander, Kendra Nash, Ned A. Tisserat, Whitney S. Cranshaw, and Jane E. Stewart

Abstract: Drippy blight is an emergent disease of red oaks, caused by the interaction between a kermes scale insect (Allokermes galliformis) and a bacterium (Lonsdalea quercina subsp. quercina). Multi-locus sequence analysis was used to confirm the bacterial pathogenís identity and its relationship to other phylogenetically related Enterobacteriaceae species. Further, Kochís postulates were performed on sapling red oaks. Prior to the discovery of drippy blight disease in Colorado, in the United States, the bacterium was reported on oak trees in California but was limited to acorn infections. The scale insect, A. galliformis, was previously known to occur on pin oak in the eastern United States but was not previously associated with either this bacterium or the production of significant branch dieback associated with drippy blight. In addition to a description of this new disease, this research documents a host range expansion of L. quercina subsp. quercina to northern red oak (Quercus rubra), Shumard oak (Q. shumardii), and pin oak (Q. palustris) and extends the reported host range of A. galliformis to include northern red and Shumard oaks.


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