01594nas a2200145   4500008004100000245008900041210006900130260002900199520105400228100002701282700002501309700002001334700002301354856007101377       2009                        eng d00aCollar rot on Italian alder trees in California caused by Phytophthora siskiyouensis0 aCollar rot on Italian alder trees in California caused by Phytop  bPlant Management Network3 a<p>In November 2006, trees of Italian alder (<em>Alnus cordata</em>) were observed declining in association with bleeding trunk cankers in a commercial landscape in Foster City, CA. A species of <em>Phytophthora</em> was isolated on PARP selective medium from the leading edge of the cankers. The <em>Phytophthora</em> species was homothallic with primarily paragynous antheridia and had oospores that were mostly globose and aplerotic. Sporangia were produced from mycelia on plugs of carrot piece agar in soil extraction solution and were semi-papillate and ovoid to ellipsoid in shape. The intergenic transcribed spacer region of rDNA from an alder isolate matched with 100% identity to isolates in GenBank of <em>Phytophthora siskiyouensis</em>, a recently described species associated with tanoak and found in the soil and waterways of coastal Oregon. Pathogenicity was tested on young alder trees growing in pots. Pathogenicity was confirmed on Italian alder trees and potential pathogenicity was demonstrated on red and white alder trees.</p>1 aRooney-Latham, Suzanne1 aBlomquist, Cheryl, L1 aPastalka, Tomas1 aCostello, Laurence  uhttp://www.plantmanagementnetwork.org/sub/php/research/2009/alder/