New EFB strains infecting resistant hazelnut varieties
By now you likely have heard about the new eastern filbert blight (EFB) situation. Several hazelnut orchards with the single dominant Gasaway gene for resistance have been found with extensive EFB cankers. We have seen small, poorly developed cankers on resistance trees before but not like this. Genetic analysis indicates these are new strains of the fungus that have developed here in the PNW. Research by Oregon State University faculty is ongoing but until we have more information ALL hazelnut growers need to take action this winter and spring.
New Research
The Oregon Hazelnut Commission has continuously supported and funded EFB research at OSU for many decades. Recent genetic testing has shown that the strains of the EFB fungus from orchards near Woodburn and Silverton are distinctly different from strains found in the eastern United States. They are more similar to the original strain that was introduced into the PNW than anything, for example, found in New Jersey. More concerning is that although the Woodburn and Silverton strains are closely related, they are different. Researchers believe that multiple strains of this fungus can and likely will emerge in different areas of the PNW.
These new fungal strains have been found on many hazelnut cultivars with the Gasaway gene for resistance. These trees include Dorris, Jefferson, McDonald, PollyO, Theta, Wepster and Yamhill. The infected orchards are located near Amity, Gaston, Silverton, St. Paul as well as Woodburn. Also, new strains appear to be occurring near Chehalis and Salkum, Washington. Images of cankers on resistant trees from British Columbia also look just like what has been found in Oregon.
Note: You can’t make good management decisions if you do not know how extensive the problem is in your orchard. This disease is notorious at popping up where we least expected it. The history lesson to learn is that it was always one step ahead of us. We were bad at predicting where it would go next. The point is that ALL hazelnut growers should be scouting for this disease no matter where you are; British Columbia to Eugene Oregon to Yakama Washington. Everyone is at risk. The earlier you find it the easier it will be to manage.
If you find EFB in your orchard of resistant trees, please prune off 5 to 10 cankers and send them in to OSU for testing. Please include contact information, location (GPS best), variety, age of planting, and estimated percentage of trees infected. We are specifically focused on EFB symptoms on resistant varieties that are showing black stromata, possible flagging of leaves, and evidence of aggressive canker growth. The more samples we get the better we can access the situation. Send samples to: Nik Wiman, OSU Extension Orchard Specialist, Jay Pscheidt, OSU Extension Plant Pathologist, or Colleen Nihen, Executive Director, Hazelnut Industry Office.
The Woodburn strains found on Jefferson trees have been inoculated onto other trees. This research is still continuing but it appears that McDonald (with the Gasaway gene) and Sacajawea (with quantitative resistance) are highly susceptible. Stay tuned as there is likely more information to come from this aspect of the research.
A new area of fungicide research has been focused on drenching the ground instead of spraying the canopy. Initial results with the FRAC 3 chemical (Rhyme or Topguard) have been encouraging. Right now the chemical is labeled for foliar applications as well as through a drip or microsprinkler system. This research can be found here: http://sites.science.oregonstate.edu/bpp/Plant_Clinic/Fungicidebooklet/2024/index.htm
The OSU hazelnut breeding program is still quite active. A major emphasis of crosses in 2025 will be focused on quantitative resistance. Quantitative resistance generally results in fewer and smaller cankers. Different sources of resistance will be “pyramided” (bread) into new varieties. Trials with these other resistance sources are underway. New promising selections are close to development but many still rely on the Gasaway gene.
Summary
Bottom line: We know what it takes to manage EFB, a combination of scouting, pruning and fungicides. It has been fantastic to use resistant cultivars and not have to manage this disease as hard but that time has passed. The new cultivars already in the ground still have other useful horticultural characteristics, new ones are on the way and optimism still resides for the future of this industry.
Acknowledgement
The research discussed is ongoing and from many different laboratories including those led by Dr. Nik Wiman, Kameron Kilday (Dr. Ken Johnson), Dr. Alexandra Weisberg, Dr. Jared LaBoldus, Dr. Alex Zaccaron, Dr. Tom Molnar and Dr. Shawn Mehlenbacher.
Please note the following resources that can help you understand the biology of this unique disease and give management recommendations: