Weekly Tree Nut Report: Crack-Out Audits, Pistachio Blight and Potassium

The Weekly Tree Nut Report from West Coast Nut arrives every Wednesday with field intelligence for California almond, pistachio and walnut growers and their crop consultants. Subscribe free to get it by email.

Research through October 16, 2026 (Pacific). This week’s priority: document what failed, separate look-alike causes and budget corrections by block. The new pistachio shipment report updates the market picture.⁶ The field briefs below apply clearly dated UC guidance to postharvest decisions; they do not report new local outbreaks.

This week in numbers

• 1,000: Nuts per block in UC’s recommended walnut harvest-damage sample¹
• 20%: Rise in irrigation-water EC that should trigger a new lab test for SAR and specific ions⁴
• +40%: September pistachio shipments, 88.42 million lbs, vs. September 2025⁶

For PCAs: Pest and Disease Management

1. Walnuts: turn crack-outs into a timing audit

Seasonal reminder · UCCE, Sept 17, 2017

For California blocks still harvesting, UCCE recommends a representative 1,000-nut sample per block, taken from multiple locations and proportionally at each shake. In windrows, sample through the pile, not just the top layer, because lighter, infested nuts can concentrate on top. Refrigerate samples, remove hulls within a few days of collection, and record any hull infestation or damage.¹

Separate navel orangeworm from codling moth by larval markings: NOW larvae have a dark crescent on either side of the second segment behind the head; codling moth larvae lack them. Heavy webbing supports NOW identification. Black hulls alone do not establish husk fly injury, since disease, sunburn and secondary vinegar-fly larvae complicate diagnosis. Insect developmental stages help reconstruct infestation timing.¹

Next step: Produce a block-by-block damage ledger with the sample denominator, pest identification confidence and photographs. Match larval stages and damage distribution to trap, treatment and harvest dates before changing the 2027 program. For blocks already harvested, record whether retained samples represent the orchard or only a processor lot.

Source: UCCE: harvest damage evaluation for walnuts

2. Pistachios: confirm Botryosphaeria before planning control

Seasonal reminder · UC IPM text updated Oct 2014

In California pistachios with blighted clusters or shoots, inspect retained rachises and cankers; infected rachises can hang on the tree and carry inoculum for three to four years. A quick field check helps separate look-alikes: a finger rubbed on an Alternaria lesion turns black. Late in the season both fungi can be present in the same lesion, and microscopic identification may be needed.²

UC’s BUDMON protocol runs from February to mid-March: randomly collect 100 flower or vegetative buds from each orchard quadrant for laboratory testing. The guideline identifies 4–8% infected buds as moderate risk and advises considering treatment at moderate-to-high risk. Those percentages describe laboratory bud infection, not October visual counts.²

Next step: Deliver a marked-tree sanitation map and a winter laboratory sampling appointment. Confirm ambiguous lesions before assigning disease-specific control. For confirmed disease, document infected-wood removal and keep sprinklers from wetting the canopy. Use disease history and properly timed tests to build the spring timing review, and audit fungicide mode-of-action groups when selecting a program.²

Source: UC IPM: Botryosphaeria in pistachio

3. Orchard weeds: map escapes before changing chemistry

Seasonal reminder · UCCE, Oct 1, 2019; updated July 16, 2021

UCCE’s postharvest scouting guidance calls for separate inspection of treated tree rows, row middles, borders and row ends. Record species, location and infestation severity, and repeat scouting through winter to catch young weeds. Mature weeds are harder to control, and similar-looking species can require different approaches.⁵

Next step: For almond, walnut and pistachio blocks, deliver a georeferenced escape map with growth stage and treatment history. Before assigning resistance, review identification, application coverage and timing, and flag unexplained survivors for further investigation. Use the map to compare localized mechanical, cultural and labeled chemical options, including modes of action. Revisit mapped patches after action and record survival. Treat this audit as a decision record, not a validated resistance test.

Source: UCCE: postharvest weed scouting

For CCAs: Nutrition and Water Management

4. Almonds: budget potassium by variety

Research to apply · UCCE, Oct 3, 2024; updated Oct 4

Sacramento Valley UCCE describes potassium-associated leaf burn that differed among almond varieties, so an orchard-average fertilizer budget can undersupply a heavier-bearing variety. The article uses 95 pounds of K2O per 1,000 pounds of kernel crop to describe crop demand; this is a budgeting input, not a fertilizer prescription.³

Compare variety-specific yield, applied K and leaf-test records, keeping the tissue, collection date and units. UCCE cautions against potassium chloride where rootstocks are chloride-sensitive, such as Lovell and K86 (Krymsk 86), or where a perched water table limits drainage. In-season potassium sulfate should go in the wetted zone of the microsprinklers or drip emitters.³

Next step: Produce a variety-level K balance and placement map before purchasing inputs. Where symptoms and tests disagree, keep the diagnosis open and plan separate variety samples next season. Record rootstock and drainage constraints when comparing K sources, and don’t use the crop-demand figure as this fall’s application rate.

Source: UCCE: playing potassium catch-up

5. Almonds and walnuts: diagnose water quality before leaching

Research to apply · UCCE, Apr 14, 2021; updated Apr 22

UCCE distinguishes salinity, which impedes water uptake, from sodium-related soil dispersion and specific-ion toxicity, so trees can show salt-related water stress even with ample water in the root zone. ECw measures the salinity hazard; sodium (SAR) and specific ions such as chloride and boron need laboratory analysis.⁴

For blocks using marginal water, test soils at several root-zone depths, ideally to at least three feet, to set a baseline, and check for a clay layer or other soil-profile problem that would make leaching difficult. UCCE recommends a new laboratory analysis, including SAR and specific ions, when monitored irrigation-water EC rises 20% or more; that is a retesting trigger, not a crop-injury threshold.⁴

Next step: Prepare a depth-by-depth salinity profile and an irrigation response plan that distinguishes salt accumulation, infiltration limits and uneven delivery. Inspect emitter performance alongside laboratory results. State what additional drainage evidence is needed before committing water; any amendment decision should address the diagnosed limitation.

Source: UCCE: irrigating with lower-quality water

Market snapshot: Shipments in Context

New pistachio report · Almond and walnut figures carried forward

ACP reports September pistachio shipments of 88.42 million pounds, versus 63.08 million a year earlier: a calculated 40.2% increase. Exports rose while domestic shipments declined. September is also the first month of the 2026/27 crop year.⁶

Pistachios September 2026 · new	88.42 million total reported product pounds, versus 63.08 million in September 2025.6
Almonds August–September 2026	422.64 million kernel-weight pounds, versus 355.06 million in the same months of 2025.7
Walnuts September 2026	5,177 inshell short tons versus 2,509; 15,512 kernel short tons versus 9,461, compared with September 2025.8

Almond figures were released October 13 and walnut figures October 8; both are carried forward from last week’s edition. Pistachio totals combine ACP’s reported product categories, not kernel-equivalent pounds, and walnut inshell and kernel figures stay separate.^6–8

Next step: Compare handler movement and quality deductions with your own settlement outlook; shipment growth does not establish a grower return.

Sources: Pistachio shipments (PDF) · Almond position report (PDF) · Walnut shipments (PDF)

From West Coast Nut magazine

What I’m Watching: What Harvest Is Telling You About Next Year’s Crop

By Gary Osteen, PCA, CCA · September 26, 2026

After 45 years walking California fields as an independent PCA and CCA, Gary Osteen’s message to almond, pistachio and walnut growers is that harvest is not the finish line: the weeks right after harvest shape how trees enter dormancy and start next season.

Read the article · Browse the latest issue

What are you seeing?

What is your crop, county and biggest field concern? Email info@jcsmarketinginc.com and tell us.

Editorial note: “Next step” passages are West Coast Nut’s editorial recommendations; the findings before them are attributed to the numbered sources. Orchard-specific judgment, current product labels and applicable requirements govern management. This report does not award CE credit.

Sources

1. Emily Symmes, UCCE Sacramento Valley Orchards, “Harvest Damage Evaluation for Walnuts,” September 17, 2017; sampling and identification.
2. T. J. Michailides, UC Statewide IPM Program, “Botryosphaeria Panicle and Shoot Blight,” Pistachio Pest Management Guidelines, text updated October 2014.
3. Katherine Jarvis-Shean, UCCE Sacramento Valley Orchards, “Playing Potassium Catch-Up?,” October 3, 2024; updated October 4, 2024.
4. Katherine Jarvis-Shean and Allan Fulton, UCCE Sacramento Valley Orchards, “Irrigating with lower quality water? What to consider first.” April 14, 2021; updated April 22, 2021.
5. Adapted by Drew Alonso Wolter, UCCE Sacramento Valley Orchards, “Increase Your Return on Investment with Post-Harvest Weed Scouting,” October 1, 2019; updated July 16, 2021.
6. Administrative Committee for Pistachios, “September 2026 Inventory Shipment Report (Pounds),” October 15, 2026, p. 1.
7. Almond Board of California, “Almond Industry Position Report, September 2026,” October 13, 2026, p. 1.
8. California Walnut Board, “Monthly Shipment Report, September 2026,” October 8, 2026, pp. 1–2.