David Doll2 CommentsMarch 5, 2023General, Horticulture

Frost damage to almonds

Almonds are susceptible to frost once they begin to flower. As a flower progresses through bloom (i.e. dormant > pink bud > full bloom > petal fall > small fruit), it becomes more susceptible to cold temperatures. Frost killed flowers/small fruits are easy to identify as the color of the tissue changes. Flowers affected by bloom often have wilted petals or blackened pistils. At petal fall and later, the damage often appears as brown or black tissue within the ovary. This can be identified by cutting the flower/nutlet in half. The photo provides a comparison of flowers affected by frost and a healthy flower. Note the darkened, off-color tissue of the three flowers on the right. All of these have been killed by the frost. Flower sensitivity to cold damage has been studies. Additional information on this can be found here.

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David Doll0 commentsApril 25, 2022General

Re-evaluating operational costs for a difficult year

2022 will be a difficult year. Increased input costs, including water, fuel, and fertilizer, and decrease crop pricing will impact the operational expenses and crop revenues significantly. Many operations will struggle to maintain cash flows through the year. Operational costs should be closely evaluated to determine if savings are possible. Some expenses may be reduced on a short-term basis until pricing improves. Others may be eliminated from the current and future budgets due to more efficient management. A list of things to consider in helping reduce costs for the coming year include: Balance nitrogen rates. Typically, nitrogen budgets utilize a nitrogen use efficiency factor of 70%. By integrating more frequent, smaller applications of nitrogen, it is possible to assume a much higher utilization ratio – maybe closer to 85-90%. This could reduce nitrogen needs by 15-30 lbs/acre without impacting tree performance. Mid-summer leaf samples can provide feedback to this process (target range 2.2-2.5%). Test groundwater and accounting for nitrogen content. Groundwater in many parts of the San Joaquin Valley contains nitrate-nitrogen. If groundwater is used to irrigate orchard and it contains nitrate, make sure to account for the nitrogen and reduce the nitrogen budget. Balance potassium applications with any compost usage. The amounts of potassium and phosphorus within compost contribute to the nutrient budget of the orchard. Testing compost and accounting for moisture percentage should provide an estimate of the nutrients applied. This can reduce the need for fertilizers containing potassium and phosphorus (as well as many micronutrients). Review annual soil samples to determine if certain nutrients are not needed to be applied. It is common to see very high phosphorus amounts within CA soil samples and additional P may not be needed. Additionally, many loamy to clay containing soils contain potassium reserves. If the amount of potassium is high

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David Doll4 CommentsMarch 6, 2022General

Considerations for March 2022

March is a month full of surprises. Weather can be highly variable, with rain, risk of frost, and heat waves all being possible. Below are some points to consider as the season progresses. Ongoing frost concerns. Frost conditions can occur through the end of March. Maintain a watchful eye on the weather conditions to reduce the risk of any frost event. Critical temperatures after petal fall are around 28F (-2.2C), and temperatures at or below 28F for an extended period will cause crop loss. Micro-irrigation can increase orchard temperature by a few degrees, with higher flows of water providing a greater warming effect. More on frost mitigation can be found here. With irrigation occurring during multiple frost events, it is common to see trees push slow and with pale green growth. This is due to saturated rootzones that lead to loss of fine feeder roots and low micronutrient uptake. Soil irrigation levels should be monitored, and irrigation withheld until stored soil moisture begins to drop. Furthermore, nitrogen applications should not occur during the period of frost risk as running water for extended periods of time will leach nitrogen out of the rootzone. Crop losses from frost are hard to define in early March. Frost affected flowers will have blackened tissue inside the ovary, or flowers may appear blighted and remain on the tree. Trees will slightly compensate for loss of flowers with a slight increase in fruit set percentage of the remaining flowers as well as greater nut size. Therefore, in areas of minimal damage, the impacts might not be observed. In areas with losses greater than 10%, yield reductions should be expected. If frost damage is suspected, it is important to contact any insurance company as soon as possible and trim the early season fertilizer applications until a better

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David Doll0 commentsNovember 29, 2020General, Horticulture

Factors to Consider when Determining Honeybee Hive Needs for Almond Orchards

Determining the number of hives to rent for an almond orchard can be challenging. With a strong reliance on honeybees for pollination, placing too low of number of hives and bees can reduce crop potential, especially in inclement weather, while placing too many increases operational expenses. To determine the proper hive strength for the almond orchard, the following factors should be considered: Varieties present within the orchard Age of the orchard Strength of the hives contracted Crop insurance requirements Anticipated weather for the orchard’s production area; Presence of other pollinators. Almond Varieties within the orchard. All almond varieties benefit from having pollinators present during bloom. In California and Australia, the primary varieties planted are ‘Nonpareil’ and the selected compatible, pollinating varieties. Since these varieties, as well as others (e.g.’Butte’/’Padre’), require cross-pollination to set a nut, bees are required to maximize orchard yields. Due to the requirement for cross-pollination, the recommendation by the University of California has been to place two 6-8 frame hives per acre (5 hives per ha) to maximize pollination (Micke, 1996). In Europe and more recently in California and Australia, self-pollinating almond varieties are present. These varieties do not require pollen from a compatible variety to fertilize the flower. In these orchards, bees are not required to set a commercial crop, but they have shown to increase yields. In Europe, studies have shown yield increases between 5-20% amongst European varieties. In California, the presence of honeybees has shown to increase yield by 20% or more within ‘Independence’ (Saez, et al, 2020).  These studies indicate that bees should be placed to optimize pollination, but suggest that the number of hives per acre can be fewer. In Europe, 1-1.25 hives/acre (2-3 hives/ha) are common stocking rates within orchards that utilize bees. This may be a reasonable range to consider

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David Doll0 commentsMay 30, 2020General

Field Note: Simple Technique to Shave Down Tree Stakes

Written By Cameron Zuber, Staff Research Associate, UCCE Merced Have some tree stakes that do not fit into your post-pounder or lost the point making it hard to drive into the soil? Try using a shovel to shave down the stake first. Using a shovel is an easy and safer alternative to axes or knives as the cutting motion and blade edge is away from the user. It is also readily available and something people normally are willing to be a bit rough with when using. A proper technique when using a shovel to shave down a stake is: Place the stake on flat ground. Stand on the end you are not shaving down and place your back foot on the stake. Have your other foot planted firmly on the ground to help you balance when shaving the stake. Place your hands comfortably far apart along the handle. One hand should be towards the top of the handle to provide more force when shaving. The other should be place as close to the shovel’s blade to help direct the shovel tip to properly hit the stake. Angle the shovel’s blade at an approximate 20° to 30° angle from the stake. If the stake is rectangular, direct the shovel’s tip at the corners of the stake not the flat edges. Starting away from the cut end of the stake, push the shovel forward working with the grain of the wood. Continue shaving down, working towards the cut end of the stake. If trying to make into a point, angle the shovel’s blade at an approximate 45° angle as you get closer to the cut end of the stake. Otherwise keep the same 20° to 30° angle as you work towards the cut end. Repeat on all corners of rectangular stakes or

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David Doll0 commentsNovember 7, 2019General

Tree Loss Value Calculator

Unexpected tree loss happens. Whether it involves flooding of a field by a broken pipe, an inattentive driver, a natural disaster or some other circumstance, tree loss can occur within an operating orchard. A common question is how to value trees that have been damaged or lost due to various circumstances. Valuing trees is not as straight forward as it may seem. Many would assume that to replace a tree, the expenses are limited to the removal, clean-up and replanting of the tree. Although this is true, this does not represent the full investment of that tree. To fully account for the loss, applied operational expenses and lost yield must be considered.  These values for yield and operational expenses, however, must also take into account that a replanted tree will grow into maturity, and produce similar yield as other trees within the orchard. This would need to value the lost yield for the first 3 years of growth as well as the increasing yields until maturity. This calculation is not so straight forward. Thankfully, there is a tool to help estimate tree loss. A “Tree and Vine Loss Calculator” has been developed by the University of California Agriculture Resource and Economics group at UC Davis. This simple spreadsheet application provides the ability to enter in specific orchard details to determine the value of the tree(s) lost. It considers the operational expenses applied prior to the tree loss, as well as the replanting expenses and yield loss until the new tree begins to crop. Orchard specific characteristics should be entered into the spreadsheet to provide a better estimate. This includes tree removal and replanting expenses, yields and spacing. Operational expenses are based on the cost studies developed by the University. Since the cost studies are regionally developed, the appropriate calculator should

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David Doll6 CommentsFebruary 6, 2019General, Horticulture

2019 Almond Bloom Considerations

Almond bloom is just around the corner. This “start” to the season is an important period for almond production as flowers require reasonable weather conditions for pollination, fertilization, and eventual fruit set to occur. With that in mind, below are a few considerations for this period. Rain or conditions favoring dew can increase the amount of disease. Pathogens affecting almond flowers are ubiquitous in the environment, and therefore the condition that influences infection are periods of leaf wetness. Fungicides should be applied to protect the flowers from rain-splashed spores and subsequent infections. Newer class fungicides can move into the upper cell layers of the flower and kill infections, but this “reach-back” potential only provides about 2-3 days of “cure” after a rain event. Start the spray program with fungicides that are most effective for blossom diseases, but provide limited protection for petal fall and spring-time diseases. This typically includes the FRAC groups 1 and 9. As bloom progresses into petal fall, other fungicides should be considered to manage anthracnose, green fruit rot, shot-hole, and scab. FRAC groups 3, 7, 11 or combinations of these products should be considered. Remember to rotate away from fungicide FRAC groups used in previous sprays. This will help reduce the formation of resistance within pathogens, increasing the “shelf life” of a fungicide. To assist with this, especially if rainy conditions are expected, consider utilizing a broad spectrum material at petal fall or shortly after this period to provide the ability to use strobilurins and DMIs (FRAC 11 and 3) for scab and rust control. Some good rotational, broad spectrum products include chlorothalinil (FRAC M5), Ziram (M3) or Captan (M4). Don’t forget about the bees. Honeybees are brought into the orchard to provide pollination services – a requirement for production for most California type almond varieties

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David Doll34 CommentsNovember 8, 2018General

Job Transition: Departure from UC Cooperative Extension

Dear friends and colleagues, For the past ten years, I have worked within Merced County focusing on tree nut production within California.  Much of  the effort was focused on extending relevant research based practices to industry members within California and conducting research that would help solve problems within the region. Over the years, my research program within the County has been broad – with projects on maximizing water application, managing replant problems within almonds, and a variety of smaller projects within horticultural, disease, and general agronomy. All of these plots were conducted within farmers fields, in which I am grateful for the local collaboration. Recently, I have decided to take a position within farm development and leave my position within extension.  This role will start in mid-November and will be responsible for developing a diversified specialty crop farm from the ground up. My new home base will be Evora, Portugal, which is about an two hours outside of Lisbon. As one could imagine, this was a difficult decision for me -the hardest decision I have made in my life. I have been blessed with wonderful colleagues and farmers, all whom have become friends over the past 10+ years. I will miss the interactions that we had through interactions within the County and at Industry event. With this departure, I still hope to assist the industry. I plan to continue “The Almond Doctor” to provide insight to a variety of aspects of almond production.  I would imagine that topics may have a different tone, and a redesign is planned. Regardless, I look forward to continuing the effort within this platform and hope it will provide assistance for the future. Thank you for you understanding through this period of transition. I look forward to seeing all of you at the various industry

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Cameron Zuber2 CommentsSeptember 16, 2018Field Notes, General, Irrigation

Field Note: Securing Irrigation Tubing

While conducting surveys across Merced County, I have noticed diverse ways growers secure the ends of irrigation tubing.  Many are attached using some type of stake made of wood or PVC in which the tubing is tied. Other orchards have the lines wrapped around a tree and used as an anchor for the line. Finally, some of them are staked directly into the ground. Irrigation tubing moves because of expansion and contraction of the plastic caused by temperature changes, as well as, from the water and air moving through the irrigation system. Securing the tubing creates tension that helps prevent the tubing from moving. These keeps the emitters and microsprinkers in place which helps maintain good irrigation efficiency. There are a few problems with securing the tubes. The first is the added cost and time to first secure the tubing and then maintain how the tubing was secured. Secondly, the lines may contract after fixing, which can pull them off the riser. Finally, the lines, if wrapped too tight, can cut into and girdle the tree. All of these are preventable. If you do choose to secure the end of your irrigation tubing, below are some considerations to take into account: Leave some slack in the tubing: Due to changes in temperature, plastic tubing expands and contracts. When tightly secured tubing contracts, coupling points may become undone (e.g., at the riser) or may cause the plastic in the tubing to stretch, creating weak points that may eventually break. Be wary of using trees to secure tubing: While this may cut down on supply costs, make sure it does not begin to girdle the tree. Do it right: Since you are taking the time (and money) to secure your tubing, be sure to do it right. There is a lot of power

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