Effects of Benzimidazole Compounds for Dutch Elm Disease Control on Wood Surrounding Elm Injection Sites. M. W. Andrews, Graduate Student, Department of Plant Pathology, University of Minnesota, St. Paul 55108. R. A. Blanchette, Assistant Professor, and D. W. French, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 66:495-498. Accepted for publication 4 September 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-495.

Two benzimidazole compounds, thiabendazole hypophosphite (Arbotect 20-S) and methyl 2-benzimidazolecarbamate phosphate (Lignasan BLP), were injected into elms (Ulmus americana) at ground level or in root flares to control Dutch elm disease caused by Ceratocystis ulmi. Trees harvested 9 mo after injection had significantly more discoloration around Arbotect 20-S injection sites than around Lignasan BLP or water injection sites and noninjected wounds. Scanning electron microscopy demonstrated the lack of tyloses in vessels immediately surrounding the Arbotect 20-S and Lignasan BLP injection wounds. Benzimidazoles appear to alter the normal defense response of the tree and change the sequence of microorganisms that colonize elm wood after wounding. Procedures to minimize internal injury are presented.

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