Mycoplasmalike Organisms, Cause of Lilac Witches’-Broom. C. R. Hibben, Brooklyn Botanic Garden Research Center, Ossining, NY 10562. C. A. Lewis, The Morton Arboretum, Lisle, IL 60532; and J. D. Castello, Department of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry, Syracuse 13210. Plant Dis. 70:342-345. Accepted for publication 3 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-342.

Witches’-brooms developed in Syringa × josiflexa, S. × prestoniae, S. sweginzowii, and S. villosa × sweginzowii in the lilac collection at The Morton Arboretum, Lisle, IL. Associated symptoms included proliferation of axillary shoots, shortened internodes, and stunted leaves. Mycoplasmalike organisms (MLO) were detected in phloem sieve tubes of leaves by Dienes’ stain and transmission electron microscopy. MLO were also detected in lilacs with symptoms limited to premature growth of buds. Witches’-brooms developed in a lilac infected with MLO by graft transmission.