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

Fig. 4. Symptoms on stems of three alder species that were wounded and inoculated with P. siskiyouensis (in carrot piece agar plugs) or not inoculated: (AAlnus rhombifolia, inoculated (left) and not inoculated (right).



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