David Doll4 CommentsSeptember 28, 2020Horticulture

Should California consider European Almond Cultivars?

Over the past few years, I have visited several almond orchards across Spain and Portugal that are producing European cultivars of almonds. These orchards are of all shapes and planting methods, including super high density, modern high densities (115-180 trees/acre), trees with an upright, bushy, or semi-upright structure, and various pruning methods. Cultivars planted included releases from the 1970’s through releases from the past ten years. These varieties are characterized by their hard-shell/low kernel turnouts, self-fertility, later blooming, and higher fat content. Production in these orchards is highly varied. Production within most plantings is less than what is expected in California (i.e. 2000 lbs/acre is a good yield), with ranges observed from 1000-3000 lbs/acre. It is hard to determine the reason for such a wide range in yields because of the number of variables involved. Many plantings are grown in water-limited environments (~60-80% of full irrigation), have varying development practices, as well as shorter growing seasons. Furthermore, nearly all the European cultivars have a lower crack out (~30-40% in comparison to 45-60% for California varieties), which impacts yield. Unfortunately, direct comparisons to “California” cultivars are few. This prevents direct comparisons of bloom timing, production potential, and production operational expense. European cultivars, however, may have some characteristics that would be useful within California production systems. These characteristics include: Self-fertility. Due to the ability for the pollen to pollinate and fertilize flowers on the same tree, these cultivars provide several advantages to most CA type orchards. This includes the planting of solid blocks, reduced bee requirements, and easier irrigation management during critical times. Beehives do seem to provide a yield response, and it is estimated that 0.5-1 hive/acre would be needed to maximize yield. The release if the California cultivars ‘Independence,’ ‘Shasta,’ and other soft-shell, self-fertile almond cultivars provide these similar benefits.

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David Doll0 commentsAugust 31, 2020Horticulture

Stuck Nuts: Varietal Influences

Nuts can be hard to remove during harvest for a number of reasons. They include hull rot, boron toxicity, inconsistencies in ripening, and poor irrigation practices. Causes for each of these issues have strategies that can be implemented to reduce the problem and have been highlighted in previous posts. When discussing challenges in nut removal, one major factor that is often overlooked is nut variety.  Due to differing growth habits of each variety, good nut removal may be difficult to achieve at varying points of orchard establishment. For example, Aldrich, Independence, and Wood Colony can be difficult to shake during the establishment years, while Padre is a challenge at maturity. These differences are due to tree architecture and the location of the developing nut. Tree architecture impacts nut removal because the process requires the transfer of energy from the shaker. Trees that are tall, upright, and tend to bear at the end of the limb have a lower amount of energy that is transferred during shaking. Due to the height and proximity of the limbs to the central axis, these trees often require different shake patterns or procedures to achieve the optimal removal of >99% of the nuts within the tree. Pruning to minimize height may reduce the problem for a year or two, but once the wood regrows, often redeveloping with a very vertical structure, the shaking difficulties will return and increase. It is best to try and develop these trees with a wider structure at orchard establishment. Cultivars that fall within this category include ‘Padre’ and ‘Aldrich.’ Positioning of the nut also impacts shake efficiency. Young trees that tend to bear a lot of nuts on the primary wood are very difficult to shake. This effect is two-fold: the closeness to the central access prevents energy transfer, while

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David Doll4 CommentsAugust 22, 2014Irrigation

Water Stress and Varietal Differences

A few visits and emails have highlighted differences in leaf drop patterns observed across varieties within an orchard. Full rows of trees will have yellow leaves that drop in time, characteristic of water stress while other varieties appear unaffected. These “in-field” observations suggest that almond varieties respond differently to the amount of water applied. For example, the variety ‘Monterey’ and ‘Aldrich’ have been observed to show signs of stress before ‘Nonpareil’ trees even though crop load is similar. In these cases, these trees may undergo severe leaf drop while ‘Nonpareil’ appears unaffected.

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Franz Niederholzer3 CommentsDecember 21, 2012Horticulture, Insects, Weeds

What did I learn at the Almond Board’s annual conference?

The Almond Board of California’s annual conference is a chance to connect with others in the almond industry, listen to world class researchers talk about their work, and check out a huge almond-focused trade show all at one event. The 2012 meeting was last week (Dec 11-13).  Here is a quick review of some of the things I picked up from researchers and informed industry members at that meeting…

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David Doll29 CommentsJune 30, 2012Horticulture

Independence Almond – Some Observations

Many farmers are preparing their tree orders for next year’s planting. In that regard, I have received a few questions on Independence, a self compatible variety. What does it mean to be self compatible? Traditionally, almonds require cross pollination in order to ensure profitable harvests. In other words, pollen from one variety needs to move to the flower of another variety in order for the flower to be fertilized and set a nut. This is why we have multiple varieties of differing pollen groups planted within almond orchards. The newly released variety ‘Independence,’ however, is a self pollinating variety, meaning that pollen from an Independence tree can pollinate and fertilize a flower from another Independence tree. A single variety orchard has advantages over traditional 2-3 variety plantings. The obvious benefits come from the single bloom, hullsplit, and harvest timing. This provides savings in time as it may reduce the passes through the block, and even more so for growers relying on custom spraying, harvesting. These reasons where why Butte/Padre plantings were so popular. How does the tree look? At this point, although possibly premature, with observations of the oldest block that I know – 9th leaf – and a few younger plantings, it looks good. Yields have been up and down in the oldest block, but this has been due to frost events that have occurred in the late spring. In the younger blocks, the tree seems to bear well, and appears to have a good yielding potential based upon field observations.  The trees appear to be a little smaller than Nonpareil and a little more upright. Bloom time seems to overlap well with Nonpareil, if not a day or so earlier. Any obvious disease problems? The past few years I have walked the a few blocks looking for symptoms of various

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David Doll0 commentsMarch 2, 2012Horticulture

Varietal Bloom Issues

Weak bloom experienced in an orchard:Nonpareil and Monterrey shown. I have received more calls about weak bloom on almond pollinators. These trees have low counts of fruit bud, and the vegetative buds have pushed giving the tree a green instead of white appearance. The reports have been coming in from orchards of “juvenile orchards” (7-10 years of age), which typically have yielded quite heavy for their age. Nonpareil is affected, but the later harvested varieties, which include Monterrey and Fritz, are affected more severely.   In being in these orchards, it is clear that the period of fruit bud development was affected sometime last year. Fruit bud development/floral initiation varies among varieties. Studies have shown that ‘Nonpareil’s’ fruit bud differentiates about 7-14 days after harvest, while other varieties, such as ‘Carmel’, the majority of fruit buds differentiate prior to ‘Carmel’ harvest. This timing will be delayed in cool, mild years. Tree stressed imposed during this period will reduce fruit bud set, and the buds will remain vegetative (leaf buds). Very fruit bud are found on the trees,the majority of the buds are vegetative (leaf). In regards to the weak bloom, working with the farmers, we were able to identify some of the possible stressors that may have occurred during the period of fruit bud differentiation. Although we are unsure of the exact problem(s), the ones we are considering include:1. Holding back of irrigation in order to “force” hull-split or harvest,2. Excessive foliar disease, including rust or scab, that caused defoliation,3. Improper nutrient management – usually very low potassium and boron, and 4. heavy yields that reduced the vigor of the tree, impacting growth and the number of fruiting spurs available for future crops. In many cases, more than one of these issues could have affected the orchard. In orchards that experienced defoliation to foliar disease, many

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David Doll4 CommentsFebruary 24, 2012Horticulture

Some Thoughts on 2012 Bloom

To date, the weather has been very warm, with conditions favoring bee flight and pollination, but not the various bloom time diseases. The bloom looks strong across the county. In other words – so far, so good. I have received a few calls from a variety of topics, and will post some thoughts on these topics. Next week, there looks to be a few showers moving into the area, so fungicide coverage may be needed to prevent various diseases – especially if a fungicide application hasn’t been made. If an application has been made, it should provide protection for 10-14 days, dependent upon the amount of rain received. Delayed Varietal Bloom, Weak Bloom.I have received several calls regarding delayed bloom of Monterrey and Fritz. Although these thoughts are conjecture, discussions with a few advisors concluded that post-harvest tree conditions/ practices may be the cause for these issues. Tree conditions include defoliation of trees last fall from scab and rust, water stressed from a delayed harvest, and inadequate rainfall during the dormant period. Practices that may have encouraged this separation include delayed application of nitrogen and water during the post-harvest period, and missed pre-irrigations this past winter due to lack of water. Also consider that these trees have had high yields over the past few years – with two years of delayed harvests (mid-Sep-Oct) with Fritz/Monterrey. Many people have asked about inadequate chilling being a possible cause, but ample chilling has been received. More importantly, if it was a weather effect, we would expect to see the variations in bloom time occurring across a wide area – not just in a single orchard. For example, one orchard has had an issue with the delayed bloom, while the neighboring orchard with the same varieties is blooming as expected. Birds Eating Blossoms?Catching me a bit

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David Doll2 CommentsOctober 28, 2011Insects

Late Season Varieties and NOW Infestation

I am getting several reports from consultants, growers, and processors of high percentages of Navel Orange Worm (NOW) damage on the late harvested almond varieties. These reports have varied, but in all cases, damage has exceeded the targeted rejection rate of 2%. This has caught many people off guard. So, why did this occur? The cooler spring weather experienced meant a delayed hullsplit and harvest. This delay was most pronounced within Monterey and Fritz, which were about two to three weeks behind the “normal” harvesting time.  Harvest was delayed further by the early-October rain event. This increased “hang time” of the almonds within the tree provided the opportunity for more NOW damage. These varieties were exposed to the 2nd flight (during hullsplit), the 3rd flight (during harvest and drying), and 4th flight (during drying) of NOW which led to a greater rate of infestation. Since most growers applied a single NOW spray timed at 5% of Nonpareil hullsplit, these varieties were not only exposed to high populations of NOW, but were left without any type of chemical protection. A second NOW spray timed for the hullsplit of the Monterey and Fritz would have provided effective NOW control.  Egg trap monitoring would have indicated the need to spray at this time. Keep in mind that NOW develops more quickly on new crop than on mummies. It is also important to note that almonds are still susceptible to NOW infestation even after shaking. Increased time on the ground from poor drying conditions have also played a part in increasing the levels of infestation. Shook almonds were also exposed to the 3rd flight of NOW as well as a partially emerged 4th flight, and may partly explain the high number of young larvae within the hulls and kernels. Earlier this year, Walt Bentley, UC

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David Doll7 CommentsAugust 3, 2009Insects, Irrigation

Shothole borer damage on Almond – Varietal Differences in Response to Water Stress

The water crisis on the West side of the valley has presented opportunities to see problems not typically observed in almond production. Many of these issues tend to be directly related to tree stress caused by lack of water, failure of salt leaching due to decreased winter rains, and chronic water stress from prolonged drought. Typical observations of drought stressed trees range include yellowing leaves and leaf drop in mild cases, wilted new growth during moderate stress periods, and poor crop set, thinned canopy, and scaffold die back in chronic cases. A visit was made to an Aldrich-Monterrey-Nonpareil orchard located near Los Banos, CA. All varieties were on Nemaguard rootstock. This orchard has been under moderate drought stress for the past two years as determined by the use of a pressure bomb. This year, the grower was again short on water and had to water at about 80% evapotranspiration rate for the season. The grower was concerned about clear gumming coming from multiple wounds on his trees. Orchard observations included those listed above for orchards suffering from chronic drought stress: poor vigor, thinned canopies, and reduced crop load. On the affected trees, gumming was seen extending form the graft union up to the scaffolds. The issue was predominantly found on Aldrich trees, with some strikes on the Nonpareil, and very few, if any, strikes on the Monterrey. Upon seeing the damage (Picture 1), it was very clear that it was shothole borer, Scolytus rugulosus, an insect that invades and lays eggs in the branches/trunks of stressed trees. Borer insects are able to push their eggs through the bark and into the tree. A tree that is healthy enough to elicit a response then gums profusely in order to flush the egg out of the tree’s tissue (Picture 2). This gum

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