Walnut Winter Management UCCE Resources

Jaime Ott, UCCE Tehama, Shasta, Glenn, and Butte Counties
Luke Milliron, UCCE Butte, Glenn, and Tehama Counties
Kat Jarvis-Shean, UCCE Sacramento, Solano, and Yolo Counties
Janine Hasey (Emerita), Sutter, Yuba, Colusa Counties

Take a hard look at your orchard operation: take some time to Stop, Think, Observe, and Plan.

Pre-Season Airblast Sprayer Calibration: If you’re paying to spray, make those sprays as effective as possible. Take the time now to maintain and calibrate your airblast sprayers. A properly calibrated sprayer is needed for good pest and disease control. Full coverage is especially necessary for walnut blight– if it’s not covered, it’s not protected! Check your sprayer for worn or broken parts (nozzles, strainers, pressure gauge(s), etc.). Calibrate the sprayer by measuring ground speed and spray flow. The general rule is at least 2/3rd of the spray volume (gallons per minute) through the top half of open nozzles.

Sanitation is the best insurance program against NOW; you must decide what level of this “insurance” you want to buy to help protect your 2024 crop. Your economics may not allow for shaking/hand poling, blowing berms, and then flail mowing mummies prior to next season, but remember that any sanitation is better than none.

Codling Moth Mating Disruption: If you use mating disruption for codling moth, stay the course. Mating disruption is proven effective for reducing codling moth populations and damage, with return on investment maximized over multiple years of use. Good codling moth management can also mitigate NOW infestation. If using mating disruption, order mating disruptants and hang before typical spring biofix in your orchards. Remember that you will need to use monitoring approaches that evaluate female activity as well as male activity in mating disruption orchards. BE KIND to your neighbors and let them know if you are using mating disruption, as traps in nearby orchards can be impacted.

Scale Pests: Delayed-dormant is one of the effective pesticide application timings for managing scale pests. If an insect growth regulator insecticide was used for scale within the last two years, monitoring may indicate that a spray is not needed this year.

Replanting Missing Tree Spots: Make sure you’re evaluating the chances of replant survival and follow the replanting best practices. In addition, if much more than half of the replant spot is shaded at midday, a replant is unlikely to succeed.

Irrigation System Maintenance: With the cost of water and pumping rising, dialing in your irrigation is critical. An important first step is to perform system maintenance before you start things up in the spring. Contact your local Resource Conservation District Mobile Irrigation Lab for free system evaluations:

Tehama, Butte, Glenn, or Shasta Counties- Kevin Greer, 530-727-1297 or kevin@tehamacountyrcd.org

Yolo County- Conor Higgins, higgins@yolorcd.org
Solano County- Kevin Young-Lai, kevin.young-lai@solanorcd.org or 707-678-1655 ext. 123
Sutter-Yuba-Colusa- Karandave Kang, scrcdoffice@gmail.com.

Don’t fly blind with your Irrigation Management: The cost to integrate a pressure chamber into orchard management ranges from about $10 to $20 per acre annually, with potential savings in water and electricity more than triple that cost. Careful pressure chamber use can benefit walnut orchard health, as well as achieve water and energy savings. If you are interested in the pressure chamber, you can ask your local farm advisor to come out and do a spot check on your trees ahead of an irrigation.

Looking for Cost Savings Season-Long: For 2024, there are other cultural and pest management options to improving your profit margin. We have articles that focus on labor and cost cutting considerations appropriate to each season, while discussing which operations you should not scrimp on.


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