Plant Disease Management Handbook

Cause There are many different organisms that can cause leaf spots on penstemon. Puccinia palmeri and Puccinia pentstemonis are rust fungi that has been reported on penstemon throughout the PNW. A few other Puccinia species have also been reported from WA. Ramularia nivosa is common on penstemon species and reported throughout the PNW as well.

Photinia-Crown Gall

The University of Idaho Department of Entomology, Plant Pathology and Nematology offers diagnostic services for plants at the Parma and Idaho Falls research and extension centers. We have state of the art labs offering a range of diagnostic tests from culturing to molecular diagnostics. We will also investigate the cause of various plant problems on a range of hosts and provide advice for disease management. Both labs are part of the National Plant Diagnostics Network (NPDN) and adhere to the procedures and reporting requirements required of member labs.

By C. M. Ocamb

By C. M. Ocamb

Note Several nursery plants with stem cankers have been sent into the OSU Plant Clinic. It is suspected that most are due to cold injury followed by secondary invasion by various fungi (such as Fusarium lateritium or Phomopsis sp.), oomycetes (mainly Phytophthora spp.) or the bacterium Pseudomonas.

Cause The only fungus reported on sweet gum in the PNW is a leaf spot caused by Cladosporium sp. from Oregon. The OSU Plant Clinic has gotten many leaf spot samples on sweet gum in June which are likely seen earlier in May.

Note: There are almost no reported fungi on sweet gums in the PNW. The OSU Plant Clinic has found a few fungi that tend to be opportunistic on injured shoots and branches. Injuries may be due to such events as winter injury. These fungi include Cytospora and Nectria. The Botryosphaeria canker found in eastern and southern states has not been found in the PNW.