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Willow (Salix spp.)-Marssonina Leaf and Twig Spot March 2023 Cause Marssonina sp. are fungi that have been reported from all states; M. kriegeriana was reported from Washington, and M. rubiginosa has been reported from Idaho. These fungi overwinter on fal ...

Willow (Salix spp.)-Rust March 2023 See: Hemlock (Tsuga spp.)- Rusts Cause Melampsora spp., fungi that overwinter on dead leaves and young infected twigs. Several species have been reported from all states including M. abieti-capraearum (with true fir, Ab ...

Willow (Salix spp.)-Twig Blight (Scab) March 2023 See: Apple (Malus spp.)- Scab Cause Venturia chlorospora has been reported in Oregon and V. saliciperda in Washington. These fungi survive on old willow leaves on the ground and also on infected twigs. Spo ...

Yew (Taxus spp.)-Root Rot See: Cedar, Port Orford (Chamaecyparis lawsoniana)- Root Rot ...

Youngberry Go to: Blackberry (Rubus spp.) Raspberry (Rubus spp.) ...

Yucca-Leaf Spot March 2023 Cause Coniothyrium bartholomaei, a fungus, has been found on yucca in Oregon. Cladosporium herbarum (formerly Mycosphaerella tassiana) and Kellermania yuccifolia have been reported from Washington. Phaeosphaeriopsis obtusispora ...

Zelkova-Phytophthora Stem Canker March 2023 See: Crabapple (Malus spp.)- Stem Rot Note Although it has never been reported, the OSU Plant Clinic has found Phytophthora on samples of zelkova with root rot and stem cankers. Collar rots also seem to occur wh ...

Zinnia-Alternaria Blight March 2023 See: Zinnia- Bacterial Leaf Spot Cause The fungus Alternaria zinniae has been reported on zinnia from Oregon and found many times on samples sent to the OSU Plant Clinic. The fungus overwinters in plant debris in soil o ...

Zinnia-Bacterial Leaf Spot March 2023 See: Zinnia- Alternaria Blight Cause Xanthomonas campestris pv. zinniae, a bacteria that can survive in dried zinnia leaves for as long as a year. They can reside on foliage for several months before initiating diseas ...

Zinnia-Botrytis Blight March 2023 See: Greenhouse Plants, Ornamental- Gray Mold Chemical control Best used with cultural controls. Tank-mix and/or alternate products with different modes of action to prevent building up resistant fungi. Limit the use of a ...