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Plant diseases

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Description:

Several statewide and regional programs are in place to help with your plant diseases. The OSU Plant Clinic can help you diagnose the problem while the PNW Plant Disease Management Handbook can help with solutions. Several OSU faculty are located throughout the state to also assist with plant problems.

PNW Plant Disease Management Handbook

A comprehensive guide to plant disease management in the Pacific Northwest.

Includes materials and tactics suitable for organic production and homeowner use as well as for commercial production.

Search the handbook

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Featured resources

How to collect a plant specimen for disease diagnosis

Wonder what's wrong with your plant or lawn? The Oregon State University Extension Service can help. Learn how to submit plant samples to a county Extension office for diagnosis of diseases.

Melodie Putnam, Carol Savonen | Aug 2024 | OSU Extension Catalog Peer reviewed (Gray level)

What's wrong with my potato tubers?

Learn how to identify common causes of potato tuber damage, including insect pests, plant diseases and physiological disorders.

Lane Selman, Nick Andrews, Alexandra Stone, Al Mosley | Dec 2025 | OSU Extension Catalog Peer reviewed (Orange level)

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Latest News

Wider spacing helps Oregon nurseries slow boxwood blight

Simple spacing and watering changes can protect nursery crops.

May 2026 | Impact story

OSU pruning research helps hazelnut growers cut losses

Study shows some disease management costs do not improve returns.

Jay W. Pscheidt | Apr 2026 | Impact story

OSU Extension helps lead X-disease response in cherries

Research and outreach help growers spot threats early and act fast.

Ashley Thompson, Niall Millar | Mar 2026 | Impact story

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Controlling root and crown diseases of small grain cereals

Learn strategies for managing root and crown diseases in wheat and barley.

The resource covers disease management strategies including crop rotation, proper residue handling, seed treatments and controlling volunteer cereals and grass weeds to prevent pathogen spread.

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Credit: Richard Smiley, © Oregon State University (Cropped from original)

Latest resources

Pest management guide for tree fruits: Hood River, The Dalles, White Salmon, Rogue Valley, Umatilla County

This annual guide provides tree fruit growers with the latest information on pesticides and herbicides for fruit trees. People who grow apples, pears and cherries can learn application rates and recommendations for each stage of tree growth.

Ashley Thompson, Achala KC, Jay W. Pscheidt, Nik Wiman, Christopher Adams, Andony Melathopoulos, Niall Millar, Robert Orpet | Mar 2026 | OSU Extension Catalog Peer reviewed (Orange level)

Pest management guide for wine grapes in Oregon

Learn the most effective techniques for controlling insects, weeds and disease on wine grapes in Oregon. Study strategies for controlling powdery mildew, botrytis bunch rot and spider mites.

Patricia A. Skinkis, Jay W. Pscheidt, Achala KC, Marcelo Moretti, Vaughn Walton | Mar 2026 | OSU Extension Catalog Peer reviewed (Orange level)

Why is fungus growing on my lilac, and can the tree be saved?

Q: We have several older lilacs and have been gradually pruning them back over the past few years. One of the multi-trunked trees developed a fungus on one trunk, which we removed at the base. Is this lilac tree salvageable? ...

A: View answer | View all featured questions

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Specific plant diseases

Detecting and controlling eastern filbert blight

Learn the signs and symptoms of eastern filbert blight (Anisogramma anomala), from initial detection through death of tree branches.

Jay W. Pscheidt | Feb 2023 | OSU Extension Catalog Peer reviewed (Orange level)

Hop latent viroid in hemp

Hop latent viroid is an emerging threat to Oregon hemp, causing stunted growth, brittle stems and yield loss. Learn how to prevent its spread with clean planting stock, sanitation and regular testing.

Cynthia M. Ocamb | Aug 2024 | OSU Extension Catalog Peer reviewed (Gray level)

How to protect vineyards from grapevine red blotch disease (GRBD)

Learn more about what Grapevine Red Blotch Disease is, how to prevent it, and how to test grapevines for the disease.

Patricia A. Skinkis, Justin Litwin | Feb 2025 | OSU Extension Catalog Peer reviewed (Gray level)

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Meet Our Experts

Jay W. Pscheidt
Professor and Statewide Extension Plant Pathology Specialist
Luisa Santamaria
Nursery Pathology Specialist, Bilingual Educator
Christina Hagerty
Cereal Pathology
Kenneth Frost
Plant Pathologist
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Why is fungus growing on my lilac, and can the tree be saved?

Q: We have several older lilacs and have been gradually pruning them back over the past few years. One of the multi-trunked trees developed a fungus on one trunk, which we removed at the base. Is this lilac tree salvageable? ...

A: View answer | View all featured questions

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