David Doll0 commentsJanuary 4, 2011Horticulture

Some Thoughts on Pruning First Leaf Trees

Growth inclusion and the resulting fungal infection of a five scaffold tree. I often receive questions regarding pruning first leaf trees. Many growers want to know the strategies of pruning trees. Traditionally, three scaffolds are selected, equally spaced on both the vertical and horizontal plane of the tree. This article discusses this pruning style. Currently, many growers are pruning with more than three scaffolds, and in some cases up to eight or more. Which way is better? In many ways, this decision comes down to economics. In determining if three scaffold or a multiple scaffold approach, think about how long you want your orchard to live. Pruning to fewer scaffolds will yield an orchard that has the potential to live longer than an orchard with many scaffolds. Why? Selecting scaffolds that are spaced evenly through the tree will reduce formation of canker diseases within the tree as the trees mature (15+ years). Since the scaffolds are spaced more evenly, it will take longer for growth inclusions to form, and the years of growth, and the corresponding rings of xylem, will form a stronger wood, making the tree more resistant to limb breakage. Since fungal infection of the scaffolds is delayed, orchard productivity can be maintained longer. This type of pruning is recommended for growers who don’t mind the longer wait to high productivity, but want the orchard to last a longer time (20+ years) Pruning to multiple scaffolds (5+ scaffolds) has different benefits.These trees tend to produce larger crops at a younger age. As the tree ages, the branches begin to grow together, growth inclusions form, and trees are lost to fungal infections that weaken and kill scaffolds. There is also an increased risk of wind damage and shaker damage. These trees may have to be tied longer than trees with

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Brent Holtz5 CommentsDecember 27, 2010Horticulture

Proper Almond Tree Planting

When planting a new orchard, precautions should be taken to prevent tree loss. Care should be taken to reduce direct damage to the trees. Trees should be planted as soon as possible once received from the nursery. Always cover bare roots with a tarp when transporting trees on back of a trailer, making sure to keep the roots moist. If the trees are heeled in, fumigated soil or sawdust should be used and excess moisture should be avoided. Cold storage should be avoided if possible. If cold storage is necessary, then trees should be fully dormant and the roots kept moist. Care should be taken to ensure that trees are properly planted. In heavy soils, planting on berms is recommended to help drain water away from the crown of the tree. Berms should be pulled before planting to ensure that the graft union is above the soil. Do not pull a berm after planting as this may cover the graft union. Planting depth after settling should be no deeper than in the nursery and the graft union should always be well above the soil line. Holes should be dug deep enough to accept the root system; no deeper. If a crust or soil glaze occurs, break up or slice to ensure proper root growth. Planting trees high will help reduce losses to the root disease Phytophthora. The only exception is trees grafted to Marianna 2624 plum rootstock; they should be planted at the same depth they were at the nursery to avoid suckering from the roots. When planting, try to follow some of these tips: 1. Dig a hole deep enough so the roots are spread out and not cramped, 2. plant the trees so that the nursery soil line is above the current soil line, 3. plant the highest

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Roger Duncan2 CommentsNovember 30, 2010Horticulture

Rootstocks for California Almond Orchards

Roger Duncan, University of California Cooperative Extension in Stanislaus County Joe Connell, UC Cooperative Extension in Butte County John Edstrom, UC Cooperative Extension in Colusa County Nemaguard has been the main rootstock of the California almond industry for many decades.  It is well adapted to the well-drained, non-calcareous loam and sandy loam soils common throughout the San Joaquin Valley.  Nemaguard is vigorous, immune to rootknot nematode, compatible with all almond varieties, doesn’t sucker much, has decent anchorage, and is easy to grow at the nursery.  Never-the-less, there are many situations in which nemaguard struggles.  Nemaguard, as with most peach rootstocks, is prone to lime induced chlorosis (yellowing / iron deficiency) in high pH soils.   It is also susceptible to salt toxicity (sodium, chloride & boron), “wet feet”, Phytophthora root rot, oak root fungus, crown gall and “heart rot”.  Despite the name “nemaguard”, this rootstock is susceptible to ring and root lesion nematodes.  The susceptibility to ring nematode leads to the danger of bacterial canker in orchards replanted into sandy soil.  Since 1998, UC Cooperative Extension farm advisors in Kern, Stanislaus, San Joaquin, Colusa and Butte Counties have researched several alternative rootstocks for California almond growers.  These include most of the common, commercially available rootstocks in California along with many newly available rootstocks from other countries.  While there is no such thing as the perfect rootstock, there are better choices than nemaguard where many chemical or physical soil problems exist.  Below are some suggestions for specific challenging situations. Heavy soil / poor drainage.  Nemaguard is not adapted to poorly drained soils and can become yellow, stunted or even die from lack of oxygen.  Lovell, another peach seedling rootstock, is not much better.  As a group, plum rootstocks are pretty tolerant to heavy soil.  Marianna 2624 has traditionally been the rootstock of

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David Doll2 CommentsAugust 16, 2010Horticulture

2010 Almond Harvest Around the Corner…

Harvest has started in the Southern San Joaquin Valley, and will be starting in the Northern San Joaquin Valley in the coming week. Here are some points to consider for the upcoming harvest: A few articles posted last year can provide a few tips to help with the decision of harvest timing:1. Preparing for Harvest. 2. Taking a Harvest Sample for an IPM checkup. Keep in mind that earlier harvested nuts may have to dry on the ground for 1-2 weeks, while nuts partially dried on the tree will require less time. Nuts that remain in the tree will have a longer period of susceptibility to NOW, while almonds on the ground are susceptible to ants, mold (due to increased humidity), and rain events. A quick orchard walk through looking for fire ants and pavement ants should provide the information needed for this decision. As soon as the almonds are picked-up, irrigate the trees. Adding a little nitrogen at this point is also advised. It may be possible to water the trees earlier dependent upon the irrigation system. Drip users may be able to irrigate as soon as the trees are shaken, while some micro-sprinklers may have small enough pattern that does not wet wind-rowed nuts. If stockpiling in the field, cover the almonds with a white tarp – or better yet, a two tarp system that includes a black under layer and a white tarp on top. The white tarp or b/w combo has been shown to reduce stockpile temperature and condensation, helping to reduce the environmental conditions favorable for aflatoxin production. Uncover the piles when possible to prevent the accumulation of moisture underneath the plastic. Fumigation of the stockpiles may be necessary. If rain is imminent, keeping the almonds in the tree will increase the dry time of

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David Doll0 commentsJuly 16, 2010Horticulture

Orchard Cover Cropping pt 1

Written by: Jessica Corcorran, Pomology Intern, UCCE Merced County Jessica was selected by a committee to serve in the Summer Pomology Internship Program funded by the Almond Board of California. Being assigned within Merced County, she is working on several research projects, attending farm calls, and getting a feel for what it takes to be an extension agent. It is our hope that her career path will lead to extension work, hopefully serving the almond industry within California. She is entering her Senior Year at Cal Poly. The use of orchard cover crops is not a new practice. The benefits of cover crops have long been recognized and have been widely used in agriculture. In recent years, cover crop use has increased due to a multitude of reasons which include soils health improvement, increased soil fertility, and increased water retention and penetration. In today’s post, I will cover the impacts of cover cropping on soil health. In subsequent posts, I will discuss other benefits of cover cropping, general pros and cons, as well as the practicalities of implementing a cover crop in an orchard.   Cover crops have the ability to greatly improve soil quality and structure. Water penetration is often compromised by soil compaction in orchard soils.  The roots of the cover crop and their ability to move through the soil can help to reduce soil compaction by tillage and harvesting equipment.  Plow pans have even shown to be corrected by the use of cover crops. The fibrous roots of the cover crop also help to stabilize soil aggregates, which improve soil structure and aids in effective water infiltration. The addition of organic matter in the soil invites beneficial microorganisms. During the breakdown of organic matter, indigestible compounds are formed that are resistant to decomposition. These compounds bind soil particles

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David Doll0 commentsMay 25, 2010Horticulture

April/May/June Almond Nut Development – Rationale for Proper Irrigation and Fertilization

The cool spring has brought up a few questions about almond development that I will do my best to answer today. Does the cool weather slow nut development? Yes, it does. By reducing the heating units, almond development is delayed. Similar to peaches, the cooler the weather, the longer it takes to complete the fruit sizing and kernel formation. This usually means that later season events will be delayed – such as hullsplit and harvest.   How can we determine if nut development is complete?  By pulling almonds off of tree and taking cross-sections, it is easy to observe the development of the embryo. As seen in figure 1, the embryo will grow from the tip and eventually fill the entire shell. Preceding embryo development is the endosperm and nucellus which makes up the “jelly” of the almond. The endosperm tends to be a bit more cloudier than the nucellus and proceeds embryo development. Once the embryo is completely developed (i.e. the kernel has filled the shell), weight accumulation will begin in the kernel  This generally tends to happen around early June and continue to hullsplit. Why is knowing when the completion of nut development important? Most of our UC recommended practices regarding irrigation and fertilization are based around nut development. If you are running short on water due to a curtailment, you might have heard that water can be cut back in Mid-June to help stretch your budget. This point in mid-June refers to when the embryo is completely developed and the dry weight accumulation is nearly done. Cutting water sooner than this will lead to reduction of crop weight, shrivels, and in some cases, nut abortion. In a cooler year, this point may be delayed – so if you are planning on deficit irrigating this summer, make sure your kernel development is complete.   This same principle is also the basis of most fertilizer timing recommendations. Fertilizer should

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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 Doll0 commentsFebruary 16, 2010Horticulture

Checking Thermometers to Monitor Frost Temperatures

By: Maxwell Norton (UCCE Merced) During frost season it is important to precisely know how cold it gets in various parts of your orchard or vineyard. Affordable minimum recording thermometers are available through farm stores and are usually pretty accurate but you need to check them yourself every year because they can “drift” up or down over time. The “U” shaped minimum-maximum recording thermometers are usually accurate at one end or the other but rarely both. Don’t use a “freebee” or a decorative thermometer. Fill a plastic bucket up with ice. Add enough cold water to make a slurry. Shake the bucket gently so the slurry stays loose. Insert the thermometers into the ice & water mixture so that about 2/3 of the thermometer is submerged. If it is an electronic sensor and it is waterproof, make sure it is completely submerged. Electronic devices may have a separate procedure for calibrating – check the instructions or their web site. Let the thermometers sit for twenty minutes. Pull the thermometers out one by one and immediately note the temperature. In a mixture of water and ice, the temperature should be 32F. If not, mark a correction factor on the thermometer. If it is more than 2-3 degrees off, you probably should not use it for something as critical as frost management. Thermometers should be placed in the low spots in the field that get the coolest. They should be away from and preferably up-wind from buildings, blacktop, or anything that might radiate heat at night. The thermometer should be about four feet off the ground and not be exposed to the sky – a simple “shelter” consisting of a board to attach the thermometer to with a cover extending 6-8 inches over the top works. Position the thermometer horizontally with the

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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 Doll1 CommentOctober 12, 2009Horticulture

Dealing with rain at harvest

A rain at harvest can be expensive – damage to the crop reduces the quality and premiums received from the huller, increase harvest costs reduce profit, and the use of forced air driers are costly. With rain imminent, it is important to keep in mind that practices should be employed to speed the drying of crop, whether it is in the tree or on the ground. The following guidelines may provide some help during a rain event during harvest. If rain is forecasted, do not shake trees as almonds will dry more quickly when hanging on the tree due to increased air circulation. If nuts are already on the ground, blow them away from trees but not into windrows or piles. Doing this will help prevent the nuts from sticking in the mud within the tree row strip. Once the nuts are stuck in the mud, it is difficult to move them away from the trees. Once the rain event has completed, rake the almonds frequently, turning them until they are thoroughly dry. If they are already windrowed, run them through a pickup machine and let the nuts fall out of the back. This will help turn the windrow nuts, increasing air contact, and will help remove wet debris from the pile. A table developed by Larry Reinhart (North State Hulling Company) is provided below to serve as a further guide – especially if showers or high humidity persists. Table 1: Prescribed actions for almond harvest involving a rain event. Information sourced from Chapter 35 of the Almond Production Manual:Connell, J.H., G.S. Sibbett, J.M. Labavitch, and M.W. Freeman. 1996. Chapter 35: Preparing for Harvest. Almond Production Manual. University of California, Division of Agriculture and Natural Resources. Publication 3364. Oakland, CA.

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