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Arboriculture & Urban Forestry Online
Volume 2, Issue 6 — June 1976
https://www.isa-arbor.com/Publications/Arboriculture-Urban-Forestry

Update on Phloem Necrosis of Elms    (View PDF)

W.A. Sinclair, E.J. Braun, and A.O. Larsen

Abstract: Phloem necrosis (PN), caused by a submicroscopic mycoplasmalike organism, is lethal in five elm (U/mus) species native to North America. All American elms, including those resistant to Dutch elm disease, are highly susceptible. The causal organism, which has never been cultured apart from plant or insect hosts, spreads within infected trees only within phloem sieve tubes. Infected red (slippery) elm, less susceptible than American elm, develops witches' brooms before dying. Elms of European and Asiatic origin seem resistant. The causal agent was graft transmitted to clones of two European species, U. carpinifolia and U. hollandica, in which only witches' brooms developed, while no symptoms have yet been induced in Scotch {U. glabra) or Siberian [U. pumila) elms. The PN agent is naturally transmitted by adults of the white banded elm leafhopper, Scaphoideus luteolus, and possibly by other leafhoppers or planthoppers that feed on elm. PN epidemics are usually localized. In northern areas the disease is unknown where average minimum winter temperature is lower than -15 deg. F (-26 deg. C). Remissions of PN symptoms have occurred after trunk injections with tetracycline solutions in Mississippi and New York; but in northern areas death occurs so soon after first display of symptoms that therapy of infected trees may prove impractical on account of the low success rate. Protective antibiotic treatments have not been tested. No elm population has yet been preserved in the simultaneous presence of PN and Dutch elm disease.

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https://doi.org/10.48044/jauf.1976.025


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