Lavender Diseases
Lavender has few pests and diseases. It is often promoted as a sustainable crop because growers do not commonly need to apply pesticides and fertilizers in its production. However, recently growers have been reporting plants with symptoms of Phytophthora root and crown rot (PRCR).
On this webpage, we aim to share information about PRCR of lavender and provide resources for managing the disease.
Phytophthora Root and Crown Rot
Phytophthora Diseases
Phytophthora species are microscopic organisms that cause disease in plants. Many species have been identified as the primary causes of root and crown rot of their host plants. Much of our research is focused on this group of microbes.
Resources about the Best Management Practices for managing Phytophthora in ornamental plant nurseries. Most of these management practices can be applied to control or limit the effects of Phytophthora in any system.
Resources
Presentations and Publications
Presentations
Click on the image above to view or download a presentation (pdf) we prepared for the Washington Lavender Association Meeting in Ellensburg, WA (March 24, 2017) .
Publications
- Phytophthora Root and Crown Rot of Lavender: New Host-Pathogen RelationshipsInvolving Six Species of Phytophthora and Three Species of Lavandula. (pdf) Daniel M. Dlugos, William C. Bridges, and Steven N. Jeffers. Clemson University, South Carolina
- Root rot of lavender caused by Phytophthora nicotianae, (pdf) M. Putnam, 1991. British Society for Plant Pathology. https://doi.org/10.1111/j.1365-3059.1991.tb02408.x
Contact us for a copy of the research publications.
Websites and Other Links
Phytophthora Root and Crown Rot
- Phytophthora root rot of lavender identified in Ontario (website)
- Root Rot of Lavender: Scouting is the Key to Prevention (article)
- Be on the Lookout for Phytophthora on Lavender (article)
- Pacific Northwest Plant Disease Management Handbook – Lavender-Root Rot (website)
Disease Control
Soil Preparation
- Soil Preparation for Lavender – from the USLGA website
Other Diseases and Pests of Lavender
- Managing Phytophthora Root and Crown Rot on English Lavender in the Greenhouse with Fungicides – HortScience research article https://doi.org/10.21273/HORTSCI18302-24
Diagnostics
Have a Lavender Disease Concern?
Diagnostic services are available from the WSU Plant and Insect Diagnostic Laboratory. Contact Jenny Glass for more information about WSU’s diagnostic services.
We have also prepared a guide for a technique to test your own samples for PRCR. You can view or download it by clicking the document image on the right.
Join our mailing list!
If you are interested in participating in our lavender root rot research project and/or would like to subscribe to an email mailing list about this subject, fill out the form on the right.
Lavender growers information
WSU Puyallup Research & Extension Center
2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated 9/24/2025