Collar Rot on Italian Alder Trees in California Caused by <i>Phytophthora siskiyouensis</i>

Fig. 1. Phytophthora collar rot on Italian alder trees: (C) bleeding canker at the base of a tree and a sprinkler emitter (arrow) adjacent to the trunk.



Image from Plant Health Progress article:
Collar Rot on Italian Alder Trees in California Caused by Phytophthora siskiyouensis