Every year, hungry hives are placed in orchards before the dawn of almond bloom. In growers’ experience, hives that forage on cover crops early (before bloom) are stronger in the second week of February, when almond bloom usually occurs. What’s more, cover crops planted in orchards provide bees with nutrients, allowing growers to boost their pollination potential.

In addition to providing better bee health, cover crops improve soil health in the orchard. Orchards will have better water infiltration, earlier field access, reduced compaction and better nitrogen contribution if the right mix is used. All cover crops excel at increasing organic matter, an important, yet often overlooked, aspect of soil health. Organic matter holds 18-20 times its weight in water. In fact, a 1% increase of organic matter in soil can hold up to 19,000 gallons of water per acre!

Here at Project Apis m. (PAm), understanding cover crop impact on orchards is part of our persistent tracking and funding of honey-bee-related research. Located at the nexus of two complimentary industries – almond production and pollination – PAm develops programs, such as Seeds for Bees, that fit the needs of both beekeepers and growers.

Launched by our experts in 2013, Seeds for Bees is a free bee forage cover crop program that almond growers with orchards of all sizes use to take advantage of the many mentioned benefits of cover crops. Demand for Seeds for Bees has grown steadily. Last year, the program provided 6,200 acres of cover crops to California growers, up significantly from 2,100 acres the first year. Each grower may receive a set amount of seed via Seeds for Bees funding. However, many growers with large acreage will buy additional seed outside the program to supplement coverage of their entire orchard.

Planting Cover Crops

With the aim of ensuring an early bloom, the ideal time to plant PAm cover crops is by October 5, before the first winter rains. However, some orchards with late harvesting varieties may not be ready by then. Cover crops planted after October 5 will still germinate, though the hive-strengthening aspects will be diminished. Synchronizing cover crop bloom with the bees’ arrival is the best way to take full advantage of the Seeds for Bees program.

There are three Seeds for Bees options from which to choose:

  1. PAm Mustard Mix is a mixture of Canola, ‘Bracco’ White Mustard, ‘Nemfix’ Mustard, Common Yellow Mustard and Daikon Radish. This mixture is great for adding organic matter and alleviating soil compaction in the orchard and requires the least amount of water among the three options.
  2. PAm Clover Mix is a mixture of six different species including Crimson Clover, ‘Hykon’ Rose Clover, Nitro Persian Clover, Frontier Balansa Clover, Berseem Clover and Annual Medic. Unlike the rapid fall growth of the Mustard Mix, this mix grows slowly over the winter. Clovers are nitrogen fixing plants, adding up to 84 lbs. N/acre.
  3. ‘Lana’ Woollypod Vetch is not a mixture, but a single species. Vetch, like clover, has nitrogen-fixation properties and should be planted early.

The best method for planting is direct seeding with drill equipment. We recommend an orchard/compact drill, equipment sold by companies such as Schmeiser or Great Plains. If broadcast seeding is the only option, a fine seed bed is desirable, since most of the seeds are small, like alfalfa. Ideally, the soil should be disked, cultipacked with a ring roller, planted and rolled a second time. The cover crop can be mowed or disked any time after almond bloom. If reseeding is desired, leaving plants intact until June may be necessary, however, this date will vary depending on the planting date and local climate. Reseeding of the PAm Clover Mix and ‘Lana’ Woollypod Vetch is encouraged, but the PAm Mustard Mix can be aggressive and is not a good candidate for reseeding.

A new item has been posted at "The Almond Doctor" titled "Almond Postharvest Management: Nitrogen considerations." This article highlights our understanding and some of the research regarding nitrogen management practices within almond. An excerpt:

"Interestingly, recent research suggests that late postharvest fertilization (October) can be skipped if mid-July leaf nitrogen levels are adequate (over 2.5% nitrogen). This work by Franz Niederholzer conducted at the Nickels Soil Lab in Colusa County has found no negative impact on yields when skipping postharvest nitrogen applications within orchards over the past two years..."

A link to the article can be found here:   David


A transformed image of an almond orchard using the normalized difference vegetation index.

From The Almond Doctor

Aerial imaging can provide real-time information to growers regarding water usage and crop health. Within agriculture, these tools provide a valuable service for identifying problematic areas within fields, thereby increasing efficiencies for both small and large scale producers. Currently, most aerial imaging is conducted by flights with mid-elevation aircraft or satellites. These flights and corresponding images are usually conducted by a service company and provided on a weekly or monthly basis.

Autonomous or Unmanned Aerial Vehicles (UAVs) may provide a format in which more regular flight data can be obtained. Most discussions within agricultural settings have been focused around large fixed wing drones. However, smaller, less sophisticated and less autonomous UAVs could provide a useful platform for California farmers. These smaller UAVs would be less expensive to construct, may require less regulatory permitting, and provide a mobile platform that can be quickly deployed within a field setting. In these settings, small UAVs would have the ability to quickly monitor crops for water stress, nutrient management, and pest and disease epidemics.

Almond BloomAs forecasted, the weather for bloom 2017 looks wet. This will impact the number of fungicide applications, how we apply the material, orchard access, and bee concerns. This article is a follow up to what was written last week

Periods of leaf wetness favor fungal pathogen development. Although there are no specific models for blossom pathogens, I general suggest applying a fungicide prior to a rain event in which leaf wetness exceeds 24 hours. This suggests that short, passing storms may not need a fungicide spray, but multi-day storms or multiple passing showers would. With the impending week of wet weather, fungicide applications to reduce the occurrence of disease is strongly encouraged. More on fungicide selection can be found here at the UC IPM website.

Aggregation of leaffooted by on walnut in early October of 2016. The aggregation is comprised mostly of fifth instar.

For a few seasons now, I have been interested in understanding more and ultimately finding better monitoring tools for Leaffooted bug, Leptoglossus spp.  Most growers and PCAs have a  good working knowledge of this bug and likely have attended one or more of my talks covering the subject.  We know that leaffooted bug overwinters in aggregations consisting of just a few to several hundred individuals.  The aggregations tend to occur on citrus, palm frowns, Cyprus trees, pomegranate, walnut (Fig. 1), olive, and on/in non-plant substrates like pump houses, farm equipment, and wood piles.  The list is extensive.  The reason why aggregations can occur on such a diversity of substrates is that they are not necessary interested in feeding but more so in seeking a protected area to survive winter.  An  interesting behavior that I have made is that aggregations typically occur where the group can best collect heat from the sun during peak solar radiation periods. 

2014 12 09 12.57.032Field fumigation should be considered when replanting almond orchards.

It is the time of the year when many operations begin the process of replanting almond orchards. Orchard removal and eventual replacement is one of the more critical times of farm operations. The decision to remove a block varies by farmer. Some remove blocks based on a cycle of redevelopment, meaning that blocks are removed on a schedule based on age to assist with cash-flow. Some are removed due to expensive or inadequate resources (e.g. water). Many are removed when production drops below a certain profitability level.

Removing a block on profitability can be tricky. Blocks tend to alternate bear. An off year may trigger removal, but it could be coming into an on year. Prices also fluctuate. Therefore, this may not be the best way to decide on removing a block. Another consideration should be determining the the stand of trees remaining in the orchard and the rate of tree loss over the past few years. Commonly, in old orchards, trees are lost to heart rot decay fungi and corresponding wind throw. These losses tend to increase as the orchard ages. If this rate is increasing and the orchard stand is below 75%, removal and replanting should be considered. This is a conservative estimate, and should be evaluated with production records and tree stand for your own operations (This estimate is based on an 80% canopy coverage at maturity with minimal tree losses).


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