Field Evaluation of Almond Varieties

Project No.: Hort2-3rd

Project Leader: Phoebe Gordon (UCCE Madera and Merced Counties); Roger Duncan (UCCE Stanislaus County); and Luke Milliron (UCCE Butte, Glenn, and Tehama Counties); Jocelyn Alvarez Arredondo (UCCE Glenn, Butte, Tehama); Karla Caldera (CSU Chico); Becky Wheeler-Dykes (UCCE Glenn, Tehama, Colusa); Jaime Ott (UCCE Tehama,Butte, Glenn, Shasta); Bruce Lampinen, Dept. of Plant Sciences, University of California, Davis, and Ramandeep Kaur Brar, (UC Davis)

Project Cooperators and Personnel: Tom Gradziel, Sam Metcalf, Maria Contador, Sabrina Marchand, Misha Marchand (UC Davis), Joe Connell (UCCE Butte County), Chico State University, Salida School District, and Creekside Farming Company.

Sections
A. Summary
B. Objectives
C. Annual Results and Discussion
D. Outreach Activities
E. Materials and Methods
F. Publications that emerged from this work
Tables and Figures

A. Summary

The third generation of regional almond variety trials, planted in the winter of 2014, includes 30 varieties, however 9 are no longer being followed due to poor yields, poor harvestability, or other major flaws. This trial is replicated over three locations in Butte, Stanislaus, and Madera Counties. At all locations, Nonpareil has been planted as the standard variety to compare test varieties to. Rootstocks differ at each location and were selected based on commonly planted rootstocks in the area; Krymsk 86, Nemaguard, and Hansen 536 in Butte, Stanislaus, and Madera respectively. Each test variety is replicated four times at each location. Due to an unusually cold winter and spring, bloom and harvest dates were two to three weeks later in 2023 than in previous years. Bloom and hullsplit evaluations ceased in 2022, as the average date for each site changed very little during the last several years of evaluation. The final average bloom date and hullsplit initiation and length for each location are included in this report. Yields in 2023 were less than in previous years at Stanislaus and Madera, possibly due to poor bloom weather. Despite the weather, bloom density and yields were excellent at Butte in 2023 following an off-year from freeze in 2022. Navel orangeworm damage was severe this year at the southern two sites, particularly at the Madera location.

B. Objectives

To compare new almond varieties and advanced selections against industry standards, under commercial production practices. Traits under evaluation are yield, bloom and hullsplit timing and duration, and any notable diseases or other issues that occur.

C. Annual Results and Discussion

Butte – Weather conditions were cold or cold and wet for much of the 2023 bloom. However, there was a key period from February 17 through 21st (21st was approximately full bloom in Nonpareil) where there was no rainfall and highs were between 62 and 74 allowing for bee activity. Bloom density was very strong in 2023 following a severe freeze during bloom in 2022 that reduced yields. Despite rainfall – there were no reported spring diseases in the trial. Spring and summer growing conditions were good. Harvest started approximately a month late for Nonpareil (September 19) and the 12 earliest harvested varieties (September 21). The harvest of the remaining varieties was delayed until October 9 because of a 2-inch rain event that fell after those varieties were already shaken. Due in part to the protracted hullsplit – there was extensive hull rot in the trial. Moderate to severe hull rot was noted in Nonpareil, Eddie, Capitola, Yorizane, and UCD 7-159. Despite the challenging bloom weather – yields were excellent, due in-part to the strong bloom density following an off-year. 2023 and cumulative yields, 2023 major defects, and yields over-time can be found in Tables 4, 8, and Figure 1, resepectively.

Bloom, hullsplit, yield, and nut quality

Bloom and hullsplit observations ended after 2022. Final average full bloom, relative to Nonpareil, can be found in Table 2, and final average hullsplit can be found in Table 3.

Stanislaus – Weather conditions were abnormally cold and wet during bloom at the Stanislaus regional variety trial in 2023. Between 0.30 and 0.48 inches of rain occurred each day during the week of the heaviest Nonpareil bloom, with maximum air temperatures between 46 – 50 F, with few windows suitable for bee activity. In addition, the use of high bicarbonate irrigation water continues to moderate yield in this test orchard, which is on Nemaguard rootstock. Trees in this trial exhibited yellow leaves with interveinal chlorosis well into May before soil temperatures and increased root growth improved. As a result, yield of most varieties was below 2500 pounds per acre, including Nonpareil (1652 pounds per acre). The Kester variety on Hansen rootstock averaged 3510 pounds per acre while the same variety on Nemaguard yielded only 2163 in comparison. In 2023, all varieties other than Nonpareil were harvested on October 19, at least one month later than many varieties were ready. As a result, some varieties, including Eddie and Bennett-Hickman, had high levels of NOW feeding injury. For the second year in a row, Yorizane and Jennette exhibited fairly high levels of pellicle staining from an unknown cause. Despite the very wet spring, no notable outbreaks of spring or summer foliar diseases were apparent. However, UCD 1-232, Supareil, Folsom, Kester on Hansen, Eddie, Winters, Sterling, and Nonpareil had moderate to severe hull rot at harvest. Yields, light interception, and major defects can be found in Tables 5, 10, and Figure 2.

Madera – As with the two other locations, bloom and harvest was approximately two weeks later than in previous years due to cooler than average temperatures in February and March. Temperatures were generally favorable during almond bloom, however rain likely reduced bee hours. Yields for many varieties, notably Nonpareil, were lower in 2023 than in 2022. Navel orangeworm damage was extraordinarily bad this year, a common problem in the region. Cultivars with the worst damage tended to be cultivars with thin shells and/or open sutures. Eddie in particular has a thin shell that adheres strongly to the hull, and the shell will split open during hullsplit. As a result, NOW damage was almost 30%. Damage was worse in the first Almond Board of California - 3 - 2023.2024 Annual Research Report cultivar shake than the second, likely due to a long wait between when they were ready to shake and when they were harvested due to the site manger becoming sick. Probable Carpophilus truncatus damage was observed at low rates in many cultivars. No notable diseases were observed, however an extremely severe spider mite outbreak caused significant defoliation after the second harvest. Yields, light interception, and major defects can be found in Tables 6, 9, and Figure 3.

Navel orangeworm damage was severe this year, particularly at the Madera site. Navel orangeworm damage was bad statewide in 2023, likely due to a combination of abandoned orchards and low rates of winter sanitation due to heavy rains/cost saving measures. Doubles continue to be high for some cultivars, notably UCD18-20, UCD8-201, UCD8-160, and Booth.

D. Outreach Activities

Presentation: Included as part of “Key Management Lessons in Almond and Walnut” by L. Milliron at North Valley Nut Conference – January 19, 2023. Approximately 200 attendees. Presentation: “Almond Rootstock and Variety Selection in the Northern Sacramento Valley” by L. Milliron at Butte County Grower Day – November 29, 2023. Approximately 150 attendees. Additionally, all advisors on this project have fielded many calls and emails from growers on the variety trial results. These primarily have been to get experiences and opinions with Yorizane, and a few have been on when Y117-91-03 may be released.

E. Materials and Methods:

This third generation of Regional Almond Variety Trials consists of three nearly identical field trials located in important almond growing regions of the Central Valley; Butte County (California State University, Chico), Stanislaus County (Salida School District), and Madera County (Creekside Farming Company). Table 1 contains the complete list of varieties and selections, 14 of which are partially or fully self fertile. The rootstocks used differ by location and reflect commonly used rootstocks in each region: Krymsk 86 at the Butte location, Nemaguard at the Stanislaus location, and Hansen 536 at the Madera site. The tree spacing is 18’ x 22’ (110 trees/acre), 16’ x 21’ (130 trees/acre) and 12’ x 21’ (173 trees/acre), respectively.

Bloom initiation is recorded when approximately 1% of flowers are open, full bloom is recorded when 80% of flowers are open, and the end of bloom is marked when almost all flowers have lost their petals. Bloom data was recorded three days a week. Hullsplit was considered initiated when 1% of non-blank fruit had reached stage 2c (the hull suture had opened), and completed when 100% of the fruit had reached stage 2c. Hullsplit was collected 1-2x a week, depending on the site and the speed of hullsplit progression. Bloom and hullsplit observations ended after 2022. Final average full bloom, relative to Nonpareil, can be found in Table 2, and final average hullsplit can be found in Table 3.

F. Publications that emerged from this work

Key Takeaways from Ongoing Regional Almond Variety Trials. R. Duncan, B. Lampinen, P. Gordon, L. Milliron, R. Brar, and C. Reyes. West Coast Nut. May 2023. Ppg 8-13.

Be Careful with Almond Variety-Rootstock Selection. L. Milliron, F. Niederholzer, K. Jarvis-Shean, C. Reyes, and E. Smith. Sacramento Valley Almond News. September 2023.
 

Tables and Figures

*Kester was planted at all three sites on the usual rootstock for each site. In addition, Kester was planted on Hansen 536 rootstock at the Butte and Stanislaus sites.
**Y116-161-99 was released as Yorizane in 2020.
*** Nine of the varieties were dropped from the data collection at all three sites as of 2022
 

*Bloom data for the Madera site is through 2021 only due to lost data in 2022.
 

*The average length of hullsplit was only calculated using data from 2016 to 2021; severe water stress prevented the cultivars from completing hullsplit in 2021, and for UCD18-20, hullsplit was never initiated.
 

¹Percent crackout is the percent kernel weight of the in-shell product.
 

¹Percent crackout is the percent kernel weight of the in-shell product.
 

¹Percent crackout is the percent kernel weight of the in-shell product.
²Three of the four replicates for Folsom have incomplete yields from 2016-2023, and were not included in the cumulative yield analysis. Because of this, Tukey-HSD cannot be completed, so this cultivar was excluded from the cumulative yield analysis
 

¹Brown spot/bug damage is over-estimated. Early in the quality grading process kernels with small brown spots that should have been assigned to stain/discolor (i.e. not from bug damage) were erroneously assigned to brown spot/ bug damage.
 

Figure 1: Average kernel yields kernel yields at the Butte site from 2016 to 2023. The results are averaged by year, therefore replicates with missing data are not automatically excluded from other years. Cumulative yield data may differ from Table 5.

Figure 2: Average kernel yields at the Stanislaus site from 2016 to 2023. The results are averaged by year, therefore replicates with missing data are not automatically excluded from other years. Cumulative yield data may differ from Table 5.

Figure 3: Average kernel yields at the Madera site from 2016 to 2023. The results are averaged by year, therefore replicates with missing data are not automatically excluded from other years. Cumulative yield data may differ from Table 5.

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