Jaime Ott, UCCE Tehama, Shasta, Glenn, and Butte Counties

With walnut prices modestly up, this is a good time to look at your orchard operation, grade sheets, and pest/disease challenges in the last few years and make a plan for 2025 and beyond. Consider how the 5% rule might apply, where small improvements across multiple aspects of an operation can yield large returns.

Chill accumulation has been low-to-moderate so far this winter, depending on how you count and where you grow. If you’re worried about inadequate chill in your orchard, this could be a year to explore dormancy breaking treatments. See more in this newsletter for the latest research.

Mating disruption is an effective method for reducing codling moth damage, which also helps to reduce NOW infestations. If you opt to use mating disruption, hang mating disruptants before the typical spring biofix in your orchard. Remember that these products can affect trap catches in pheromone traps in nearby orchards, so be kind to your neighbors and let them know that you are using mating disruption.

Any sanitation is better than none for NOW control. If you situation doesn’t justify the Cadillac treatment (shaking/hand poling, blowing berms, and destroying mummies by flail mowing), consider doing what you can to protect your 2025 crop.

Delayed-dormant is a good time to spray for scale pests If you have used an insect growth regulator in the last two years, monitor to see if you can skip a scale spray this year.

Take the time 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.

Perform irrigation 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, and Shasta Counties- Kevin Greer, kevin@tehamacountyrcd.org or 530-727-1297
• Yolo, Colusa, Sutter, and Yuba Counties- Conor Higgins, higgins@yolorcd.org or 530-661-1688 ext. 4
• Solano County- Kevin Young-Lai, kevin.young-lai@solanorcd.org or 707-678-1655 ext. 123
• Sacramento County- Chris Timmer, chris@sloughhousercd.org

Consider using a pressure chamber to inform irrigation start timing this spring. Careful pressure chamber use can benefit walnut orchard health, as well as achieve water and energy savings.

Follow these best practices for replanting. If more than half of the replant spot is shaded at midday, a replant is unlikely to succeed.

Look for cost savings throughout the year with these articles focusing on labor and cost cutting considerations appropriate to each season.

Check out your regional UCCE meeting this winter for the latest production research and best practices. See the calendar in this newsletter or visit the Events page on SacValleyOrchards.com.

Updated fungicide and bactericide efficacies and timing for 2025 are available now at UC IPM. Walnut-specific tables are included in this newsletter.