Survey for and Chemical Control of Leafy Mistletoe (Phoradendron tomentosum subsp. macrophyllum) on Shade Trees in Davis, California. Themis J. Michailides, Postdoctoral Research Associate VI, Department of Plant Pathology, University of California, Davis 95616. Joseph M. Ogawa, John R. Parmeter, Jr., and Shig Yoshimine. Professor, Department of Plant Pathology, University of California, Davis 95616; Professor, Department of Plant Pathology, University of California, Berkeley 94720; and Parks and Grounds Superintendent, Davis, CA 95616. Plant Dis. 71:533-536. Accepted for publication 20 January 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0533.

In a survey at Davis, CA, leafy mistletoe (Phoradendron tomentosum subsp. macrophyllum) was found on 15 species of shade trees: Modesto ash (Fraxinus velutina var. glabra ‘Modesto’), Arizona ash (F. velutina ‘Arizona’), chinese hackberry (Celtis sinensis), black walnut (Juglans hindsii), locust (Gleditsia triacanthos), Moraine ash (Fraxinus ‘Moraine’ = F. holotricha × F. pallisae), an alder species (Alnus sp.), white alder (A. rhombifolia), pagoda (Sophora japonica), acacia (Acacia melanoxylon), English walnut (Juglans regia), boxelder (Acer negundo), elm (Ulmus carpinifolia), maple (A. saccharinum), and zelkova (Zelkova serrata). Among these, Modesto ash and hackberry trees were the most frequently infected. A mixture of the herbicides 2,4-D and dicamba and the citrus abscission agent cycloheximide significantly reduced new growth of leafy mistletoe in Modesto ash, chinese hackberry, white alder, and Moraine ash trees for at least 1.5 yr after application. Posttreatment dissection of limb samples from a Modesto ash with both treated and untreated clumps of mistletoe revealed live and dead endophytic systems.