David Doll2 CommentsNovember 28, 2017General

Observations from a Trip Down Under – The Australian Almond Industry

During the first two weeks of November, I was able to attend the once-every-four-years International Research Congress on Pistachios and Almonds. This meeting was held in Adelaide, Australia in which almond and pistachio researchers (as well as some growers) attended to discuss recent research within these crops. Prior to the conference, I toured some orchard operations in the Mildura area. These orchards had the look and “feel” of California orchards and  yields in the 2700-3000 lbs/acre. Through the visits and discussions with my various hosts, issues that many of the operations were trying to manage were similar but different to what we experience within California. Below are a selection that I found interesting and thought I would share. Good water management can compensate for limiting soils. Across all of the properties I visited, the soil profile was very shallow with  18-24″ of sand before hitting a limiting layer of clay. To make matters worse, the layer of clay often had a very high pH (>9) and boron (>3.0 ppm) – which would kill almond trees. These conditions reduced the rootzone to the sand profile which has limited water and nutrient holding capacity. To compensate for these “shallow soils,” most orchards are planted on a raised bed and irrigated daily with double drip systems to match the tree’s water demand for that day. The water applied does not exceed the holding capacity of the 24″ of soil to prevent root movement into the deeper toxic soil. This practice also prevents excess water from running off or creating a perched water table. This was an “eye-opening” experience for me. We generally have the luxury of deep soils within California in which we can irrigate deeply, less frequently. These irrigation practices, however, produced tree growth and yields which were comparable to California orchards.

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David Doll5 CommentsMarch 9, 2010Horticulture

Orchard tasks to help prevent frost damage

A light frost event is predicted for Tuesday and Wednesday night. Last year, an unexpected frost event caused a lot of damage to almonds throughout the San Joaquin Valley. Today’s entry will focus on frost protection. Types of frost. There are two major types of frost events that occur throughout California. An advection frost occurs when a cold front moves into the region, displacing the warm air. These events are rare and will have temperatures dropping below freezing even though the it may windy. They are very difficult to protect against due to the rapid displacement of heat from the orchard. Radiation frosts are more common. They are characterized by clear skies, calm winds, and temperature inversions. These frost events occur due to the gradual loss of heat from the orchard. Almond Susceptibility to Frost. Generally speaking, the further the tree advances out of dormancy, the more sensitive to frost it becomes. A dormant tree is very tolerant to cold temperatures, while small nutlets are very sensitive to frost damage. At this point of the growing season – petal fall to early nutlet development – temperatures below 26F will cause significant to total loss of the almond crop, while temperatures above 28F will cause minimal damage to the crop. The small difference of 2F makes the difference, and is why frost prevention strategies can be used to reduce crop loss. Frost damage prevention.Assuming that the orchard has already been planted (Further information regarding site selection for frost prevention can be found in the UC Almond Production Manual), Growers can manage their soil moisture and ground cover to help reduce frost damage from a radiation frost event. Moisture within the soil retains heat. This heat is then radiated up into the trees during a cold night. Dry or cultivated soil usually

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David Doll4 CommentsDecember 28, 2009Weeds

Managing Resistant Weed Populations

Over the next couple of weeks, I will be presenting information regarding weed control in an orchard system. Since herbicide resistant weeds are becoming more prevalent in the San Joaquin Valley (think Hairy Fleabane, Horseweed/marestail), it is becoming more important for growers to utilize practices that reduce the chance of herbicide resistance. Herbicide resistance is defined as the inherited ability of a plant to survive and reproduce following an exposure to a dose of herbicide that would normally kill the wild type (Think: “We used to get good control of this weed with this herbicide…”). This is different than herbicide tolerance, which is the ability of a species to survive and reproduce a herbicide treatment with no implied selection or genetic manipulation that would make the plant tolerant (Think: “We’ve never gotten dependable control of this weed with this herbicide…”). Since 1980, cases of herbicide resistant weeds within California has increased from 0 to 21 reported cases. This is mainly due to the change in tillage and herbicide use practices within agriculture. In perennial crops, growers have shifted away from orchard tillage and have become more reliant on herbicide “burn downs” to control weeds in the tree rows. Glyphosate is one of the most widely used herbicides for this practice, and, until recently, has provided good control. The formation of herbicide resistant weeds is an evolutionary process that occurs due to the application of herbicides. Since most herbicides are reliant upon a single site mode of action, it only takes a minor mutation within the plants genome to become resistant. Furthermore, the high genetic diversity of weed populations provides the opportunity for weeds to contain a mutation, thus yielding an “escape.” Once the weed is unable to be controlled by the herbicide, it produces progeny that is also resistant. These

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David Doll5 CommentsDecember 7, 2009Nutrient

Potassium Applications in Almonds

Having a major role in many plant processes, potassium promotes root growth, increases kernel/fruit size, and provides key metabolic features that include the formation of starch, translocation of sugars, stomata regulation, and the formation of xylem vessels. In general, plants deficient in potassium tend to have slow growth, with small, pale leaves. Trees that are severely deficient may have necrotic tips and margins. In many cases, the leaf tip curls upwards in a common symptom that is named the “Vikings Prow” (Figure 1). Since Potassium plays a large role in tree health, it is important to maintain proper levels of the nutrient within the tree. A critical leaf value of 1.4% has been established by the University of California and current research has suggested that levels above this value do not increase yields. Recent field studies by Roger Duncan (UCCE Stanislaus) have demonstrated that leaf potassium levels in excess of the 1.4-1.6% range did not increase yield. Through the study, leaf levels between 1.4-1.6% gave the best yield results, with yield decreasing when potassium levels were below this level. Leaf potassium levels higher than this range did not increase yield, and may actually reduce yields if applied in excess. Potassium usage by the almond crop is high. Upon harvesting the hulls and kernals, potassium is removed from the orchard. Studies by Dr. Patrick Brown (UC Davis), have shown that 76 pounds of potassium (92 lbs of K2O) are removed from the orchard for every 1000 pounds of kernals harvested. From nutrient analysis of the fruit parts, 70-80% of the potassium removed by the harvest is within the hull, while the rest is within the shell and kernel. Even though a large amount of potassium is used by the almond crop, it doesn’t always mean that large applications of potassium are needed

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Brent Holtz10 CommentsNovember 23, 2009Horticulture

Pruning First and Second Leaf Almonds

Written By Brent Holtz, UCCE Madera County Farm AdvisorPruning after the first growing season is critical in determining the shape and performance of an almond tree. At this time you should select three permanent primary scaffolds that will form the framework of the tree. I have seen quite a few first year trees pruned improperly in Madera County, resulting in premature loss of tree vigor, increased susceptibility to disease, and in some extreme cases the eventual removal of orchards; all because these trees were pruned improperly their first dormant season. The primary goal of the first dormant pruning is to select three primary branches with as much space as possible between them (fig. 1-A). Wide spacing ensures the best chance of a strong branch attachment that will not split as the tree matures. The three primary scaffolds should be oriented 120 degrees apart when viewed from above (fig. 1-B). Such an arrangement reduces the chance of splitting branches, leaning trunks, and crossing limbs. If possible, one of the three primary scaffolds, preferably the strongest, should grow into the prevailing wind, usually northwest. A strong, vigorous limb on the north side helps keep the tree from being dominated by growth on the sunny south side of the tree. Pruners should also pay attention to the angle of the primary limbs when selecting them; for the scaffold angle determines whether bark will become embedded between limb and trunk. The ideal primary scaffold grows 45 degrees from the vertical and the horizontal (fig. 1-C). If the ideal limb is not present try to find limbs at least 30 degrees from the vertical or at least 30 degrees from the horizontal. Limbs that grow at too flat an angle tend to lose their vigor and upright orientation. Limbs where the bark becomes embedded will

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David Doll2 CommentsOctober 27, 2009Diseases

Almond Tree Blow-Over Problems

Written by Bill Krueger, UCCE Glenn County Periodically fall winter or spring storms with associated high winds and saturated soil conditions result in high tree losses. As an example, a March 1995 a storm brought 6 inches of rain and wind gusts up to 100 mph to the Sacramento Valley and resulted in an estimated loss of 15,000 acres of almonds worth $210 million. More recently a storm in January of 2008 with wind gusts in up to 70 mph resulted in tree losses of greater than 30% in some orchards. When trees fall over their failure can usually be classified as windthrows or wood decay related. Windthrow is when trees with sound healthy roots are uprooted as a result of strong winds and wet soil conditions. Wood decay related failures are the result of infection from wood decay fungi, which consume the lignin in the cell walls of the heartwood. Eventually these trees fall, often in wind storms. Wood decay fungi are secondary pathogens and are not capable of penetrating intact plant membranes and must rely on some type of injury to gain access. Survey work conducted by Joe Connell, Butte County Farm Advisor and Jim Adaskaveg, UC Plant Pathologist following the March 1995 storm revealed the following. Generally, as trees aged tree losses increased. Windthrow was an important factor in young orchards (Fig.1). As orchards matured wood decay became more dominant. Wood decay accounted for approximately 90 % of the tree loss in mature orchards. Of 394 downed trees evaluated: 77% had wood decay and 81% had crown gall. Crown galls function as sites of entry for wood decay fungi.Generally almonds on Marianna 2624 suffered lower losses than peach rooted trees. The exceptions included orchards in flooded areas with softened soil and unpruned orchards with dense canopies. Generally

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David Doll0 commentsAugust 24, 2009Diseases

Nematodes and Tree Growth

A grower made a request for a visit to his orchard due to poor growth by his replanted first leaf trees. The trees were replacing trees that were lost to heavy winds from the previous summer. Within the orchard, there were several different pollinators, and all of the trees were planted on Lovell rootstock. This orchard was located in a sand/loamy sand soil series, irrigated with solid-set sprinklers, with trees ranging from 1rst-15th leaf throughout the block. Often with replanted trees in an established orchard, it is very difficult to obtain vigorous growth. The trees usually are partially shaded out, receive either too much or too little water and fertilizer, and generally struggle with soil problems involved with replanting. The replants throughout the orchard were showing signs of low vigor, which include poor shoot growth, thinned canopy, and a general weak appearance (Pictures 1 and 2). The trees showed no other signs of disease on the scaffolds or trunk. Upon root excavation, a poorly developed root system was observed. There were no signs of fungal root infection or any other aggressive pathogens, vertebrate pests, or insects. Picture 1: A first leaf almond tree severely stunted by high nematode populations. Picture 2: A first leaf almond tree moderately stunted by high nematode populations. At this point, I decided to sample for plant parasitic nematodes. Sampling for nematodes is relatively easy: Remove the top 6″ of soil from the sampling locations, and use a soil sampling tube* to remove soil from the depth of 6″-18″ and place the soil in a bucket. Do this from 4-5 locations and mix the soil thoroughly within the bucket. Pull out 2-3 pounds of soil, place it in a labeled plastic bag, and place in a cooler or refrigerator until the sample can be sent to

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David Doll0 commentsAugust 18, 2009General

Almond Production Cost and Return Studies

Ever wondered what it costs to establish an orchard? Cost studies by the Agricultural Economics Department at UC Davis are available for the following regions:Conventional Micro-sprinkler Orchard in Northern San Joaquin Valley;Conventional Flood Irrigated Orchard in Northern San Joaquin Valley;Organic Sprinkler Irrigated Orchard in Northern San Joaquin Valley;Conventional Micro-sprinkler Orchard in Southern San Joaquin Valley;and Conventional Low Volume-sprinkler Orchard in Sacramento Valley.

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David Doll0 commentsAugust 11, 2009Horticulture

Preparing for Harvest

It looks as if harvesting will be underway for Merced County within the next week to 10 days, with the date occurring earlier for growers on the West and South Sides of the county. With harvest, there are many preparations that must be taken into consideration. Water Management:In order to determine the last pre-harvest irrigation, a target harvest date must be set. Approximately two weeks after the last irrigation are required to “dry down” the trees enough to minimize bark damage from shaking. This time period does vary upon soil textures, with sand and clay requiring less and more time, respectively. This depletion of soil moisture tightens the bark to the trunk and prevents damage from the shaker attachment. Also, as the season progresses, the bark adheres tighter to the trunk. Therefore, with an earlier harvest, the chances of shaker damage are increased. In soils of low water holding capacity (i.e. sand) it may be necessary to irrigate between the harvesting of the varieties. Proper water management between varieties is just as critical as water management before harvest because during this period the tree is developing the fruit bud for the coming season. Any moderate to severe water stress during this period will reduce the formation of fruit bud. Timing of Harvest:Harvest timing should be considered using the following criteria: – The need to avoid naval orange worm damage to nuts on the tree and ant damage once nuts are on the ground; – The ability to achieve maximal nut removal; – The ability to maintain yield and quantity; – Minimization of tree injury; – Availability of harvest equipment; – weather conditions that may cause crop loss or damage (i.e. rain). A few of these points are highlighted below: Damage caused by Navel Orange Worm and Ants:Early harvest prevents the

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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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