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 20, 2019Diseases

Almond Shaker Damage

Shaker damage is commonly observed across orchard operations. This damage occurs when the force of the shaker is greater than the strength of the bark, causing it to tear away from the tree. The obvious damage not only impacts tree vigor, but also provides an opportunity for infection by wood canker fungi which can kill the tree. If the shake is properly timed and executed, shaker damage can be greatly reduced (and even eliminated) within an orchard. A common misconception is that trees that are kept too wet during the harvest period will be damaged by the harvesting process. Interestingly, this has never been supported in research nor found to be consistently true across operations. Research in the mid 90’s by Gurusinghe and Shackel found that withholding irrigation during July through harvest did not reduce bark damage of the trees. To further elaborate, they found no difference in bark strength with respect to shaker damage for almond trees grown under various irrigation treatments. Irrigation treatments included a wet treatment and dry treatment, in which mid-day stem water potential (SWP) was maintained at -9 bar and -20 bar, respectively, through the month of July/August. Despite this range in tree water status, both treatments exhibited the same gradual increase in bark strength through July and August. Based on this, the researchers concluded that water stress did not influence the timing or rate of tree bark strengthening. Based on the lack of direct effect of moisture status on tree bark strength, it is thought that the damage observed in wet areas of the orchards is most likely due to the delays in ripening. Research has found that decreased water stress (Goldhamer and colleagues, 2006) and high nitrogen status (Saa and colleagues, 2016) both  delay ripening. These trees, when shaken at the same time

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David Doll2 CommentsJuly 30, 2019Horticulture

Shaking Almond Trees: When to Start

The start of shaking almond trees will soon begin in California, as well as the rest of the northern hemisphere. This process utilizes a piece of equipment which clamps to the tree and applies a vibrational force. This energy is transferred to the nut. The vibration moves the nut, which causes the tissues to disconnect at the abscission layer. Nuts then fall to the ground to finish the drying process. As the nut matures, a few physiological changes occur. Maximum nut weight for ‘Nonpareil’ occurs sometime around the first week of August. Prior to this point, kernel weight is accumulating as the sugars are turning into fats and proteins within the kernel. This conversion is what gives the kernel weight after drying. As this is happening, the abscission layer forms between the nut and the peduncle (also known as the separation zone). As the nut continues to mature, moisture within the hull will decrease and the abscission layer will become more apparent. Generally, nuts become easier to shake as they mature, but this isn’t always the case. Increased fertility and irrigation rates have increased the variability of ripening. Also, certain varieties (‘Independence,’ ‘Padre,’ ‘Wood Colony,’ ‘Price’ and ‘Monterey’ to name a few) are difficult to shake due to the incomplete formation of the abscission layer or the structure of the tree’s canopy. Diseases or toxicities (e.g. Hullrot and boron toxicity) may also make it difficult to remove nuts as gumming may cause the nuts to stick to the tree. Lastly, hull-tights, or nuts in which the hull has completely dried may not be easily removed due to the lack of weight during the shaking process. These factors will increase the mummy counts within the trees, requiring poling or a second harvest, or a more effective sanitation program. Due to these

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Franz Niederholzer0 commentsAugust 8, 2016Horticulture

Catch frame shaker sets in almonds?

Almonds are typically shaken to the ground by a side mount or boom shaker, allowed to dry where they fall for several days to weeks — depending on drying conditions and ant pressure – and then windrowed and picked up.  Once nuts are on the ground, no water should be applied to the orchard to avoid wetting nuts on the ground.  Depending on local conditions – how dry the soil was ahead of harvest as well as weather after shaking, if irrigation is applied between harvests of different varieties, etc.  – traditional harvest practices can result in water stress in the orchard, leading to measurable yield reduction in future years. Recently, some growers have moved to shaking and sweeping within 24 hours. The windrows are then conditioned (picked up, leaves and dirt blown out and dropped back on the orchard floor in a wide, shallow windrow) and left to dry out in the orchard middles.  Growers with micro- irrigation can irrigate (at least a little) once the windrows are down, reducing water stress in the orchard compared to a traditional shake-dry-windrow-pickup harvest.  This practice can reduce the time between shaking and pickup by 48 hours. Another alternative to traditional almond harvest is the use of catch frame shaker sets instead of shake-to-the-ground (no catch) machines (see photo).   Catch frame shaker sets (two machines; a shaker side and a receiver side) are used to harvest prunes and pistachios up and down the state.  Recently I watched a stock prune/pistachio catch frame set harvest almonds in a mature (10th leaf) orchard on Lovell rootstock on Class 2-3 soil at the Nickels Soil Lab near Arbuckle.   This orchard recently had the buried drip hose replaced and the orchard floor surface was rough under the trees.  A catch frame harvest was used to get

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Franz Niederholzer0 commentsAugust 10, 2014Horticulture

Odd weather at harvest, so far

Written by Franz Niederholzer, UCCE Farm Advisor, Colusa/Sutter/Yuba Counties So far, the weather in the Sacramento Valley has been unusually moist early in the 2014 harvest season.  Higher humidity and rain last week (Aug 4-5 = 0.1-0.6”) slowed nut drying just as the season began.  A chance of thundershowers is forecast for the coming week (Aug 11-15), so we won’t spring right back to the usual August weather – hot and dry.  Growers anxious to get nuts up and out of the orchard will have to wait longer than expected to deliver a dry, quality crop.  Wet nuts are more vulnerable to damage (chipped, broken and embedded shell), which can reduce return to grower.

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Franz Niederholzer0 commentsJuly 30, 2013Diseases

The Wetness Within: Managing Moisture at Harvest and within Stockpiles

Delivering a quality crop to the huller requires attention to detail in many areas including field drying, stockpile layout and materials used for tarping stockpiles.   Recent research by Drs. Bruce Lampinen (Extension Specialist, UC Davis Plant Sciences Department) and Themis Michailides  (Professor, UC Davis Plant Pathology Department) provides important guidelines for post-shake handling, pickup and stockpiling of nuts. The following are a few take-home points from their recent research report.  Some are no-brainers, others are not so obvious:

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David Doll0 commentsAugust 24, 2010Insects

Collecting a Harvest Sample – Is It Worth It?

Taking a harvest sample is simple, but time consuming. Never-the-less, it should be done because damage is hidden by the handling that occurs during sweeping, pickup, and processing. In some cases, we have found 4% more damage in harvest samples than what was indicated in the grower’s processor report.  In other words, when we found an estimated 5% damage/reject level in the harvest sample, the processor indicated a 1% rejection level. The 4% discrepency is most likely due to damaged nuts lost during the steps of harvest. Another reason for performing a harvest sample is to account for the damage that does occur in the field. Often times processors lump all worm damage together, not separating out NOW, PTB, OFM, or other worms. Ant damage often does not show up because the chewed out pellicles are blown out the back of the pick-up machine. Gummy nuts due to deficiencies, feeding, or other conditions are all lumped together. Collecting a harvest sample is easy. In each block of concern, collect 500 nuts from the ground after shaking but before pickup and place them in a paper bag. Two samples of 250, or 4 samples of 125 nuts from differing areas of the block can also be collected, but try to keep the total number of nuts per block at 500. Store the bags in a freezer until they can be cracked out. Once able to crack out the almonds, check for signs of pests and disease. Pictures of damaged nuts can seen in a previous post or at the UC IPM website. A hand-sheller can be helpful in processing many samples. It can take 60-90 minutes for each sample depending on size. 500 nuts split into 4 125 nut samples should suffice for a 40 acre block. So, is a harvest

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