Pacific Nut Producer Magazine

Tag: Hullsplit

  • Top 5 Things to Consider at Almond Hullsplit

    Hullsplit is a time when growers’ various orchard practices – proper irrigation, nutrient management, pest control and orchard monitoring – come together in an effort to maximize almond quality and yield. To assist during this busy season, we’ve pulled together a list of the top five things you should consider before hullsplit.

    1. Measuring Hullsplit Progress

    Proper detection is the first step in effectively managing the potential for myriad pest and rot issues that may occur following hullsplit.

     

    • Hullsplit typically begins in early July, starting in the early growing regions and spreading to later growing regions accordingly. The splitting of blank nuts (as much as 3–5% of the almonds) will occur about a week ahead of hullsplit and serve as a “heads up” that split will soon occur.

    • Tip: A key to identifying hullsplit is to look for an initial split in the upper and outer portions of the canopy, particularly the southwest quadrant. Once the fruit splits, hullsplit has begun.

     

    2. Spraying to Target Navel Orangeworm (NOW)

    The most effective time to spray for NOW is during its second flight, which often coincides with the initiation of hullsplit. As a confirmation that flight activity is coincident with the beginning of hullsplit, check to see that eggs are being laid on egg or pheromone traps (note: mating disruption may affect trapping). Then, when spraying, make your application no later than at 1% hullsplit. Find out more about mating disruption for NOW.

    If your orchard experiences high NOW populations, a second insecticide application may be needed two-to-three weeks after the initiation of hullsplit, and a rotating of chemistries is advised to reduce resistance development pressure. As noted in the University of California (UC) Integrated Pest Management (IPM) guidelines, be sure to consider the following before conducting a second application:

    • varieties in the orchard, particularly late harvested varieties

    • anticipated harvest dates

    • pest pressure noted from egg and pheromone traps

    • overwintering mummy load

    • proximity to an external NOW source, such as neighboring pistachio or almond orchards managed by a different entity

    As indicated in the UC IPM guidelines, Intrepid (methoxyfenozide) and Altacor (chlorantraniliprole), are preferred materials for hullsplit sprays. Pyrethriods have been used in the past, but their use should be considered with caution as NOW resistance to these materials has emerged, and pyrethriods are toxic to beneficials. If pyrethroids are used, they should be applied only be once per season. It’s imperative that you also make sure your sprayer(s) are well calibrated to improve spray efficacy and minimize drift.

    3. Manage Hull Rot from Day One

    Almond hulls are susceptible to several hull rot fungi from the beginning of hullsplit until the hulls dry, typically a month-long period of time. This period may vary, however, depending on fertilization and irrigation. Successful hull rot control is based upon effective strategic deficit irrigation and nitrogen management.

    Strategic Deficit Irrigation (SDI) 

    SDI, also known as regulated deficit irrigation or RDI, is the practice of mildly drought-stressing almond trees at hullsplit. By managing SDI, growers can reduce hull rot by 60–90% and experience a more uniform hullsplit and timely harvest. These factors may contribute to less crop damage from weather and late-season NOW flights, leading to less aflatoxin contamination, as well. What’s more, SDI reduces water use for 2-3 weeks without impacting crop productivity.

    The target period of when growers should stress trees is from the start of hullsplit through 90% hullsplit, a period of about three weeks. The most accurate way to practice SDI is to use a pressure chamber to track and maintain slight tree water stress levels, between -14 bars and -18 bars, depending on the weather. Information about the pressure chamber is available on the UC Davis Fruit and Nut Research and Information webpage.

    Growers who do not rely on pressure chambers, particularly those with a history of hull rot and a visual baseline from which plant stress can be observed, may achieve similar results by irrigating at 50% of normal tree demand, using crop evapotranspiration (ETc) calculations during hullsplit.

    The onset of hullsplit will vary according to orchard conditions; stress levels vary with soil type and other factors. In shallow soils where trees may dry quickly, growers should initiate stress when blanks start to split, usually about a week before the onset of hullsplit. On deeper, well-drained soils, it can take up to 20-to-30 days to reach mild-to-moderate stress levels. In this case, growers may want to reference UC Agriculture and Natural Resources Publication 8515 to determine when to initiate water stress.

    Nitrogen Management 

    Almond Board-funded research has found that excessive nitrogen increases incidences of hull rot. It is critical that a proper nitrogen budgeting plan, which is a function of crop load, is in place for the growing season to ensure that only the necessary amount of nitrogen is applied. Growers should also follow their nitrogen budgeting plans throughout the whole season and update their plans as actual yields become more evident. Regular updating will also allow growers to focus their nitrogen applications to the key times of nitrogen demand in almonds: For instance, application(s) during kernel fill should typically occur the during end of May through early June.

    You can find more information on nitrogen budgeting and management at Almonds.com/Nutrients.

    4. If Applying AF36 Prevail, Aim for One-to-Two Weeks Before Hullsplit

    Recently approved for use in almond orchards, the Aspergillus flavus biocontrol agent AF36 Prevail offers a supplementary approach to reducing aflatoxin contamination in the orchard.

    If you plan to apply AF36 Prevail this season, plan to do so around early July and make the application on or close to the berms so that following irrigations can wet the Aspergillus-carrying seed. Learn more about AF36 Prevail and how it should be applied in this article from the Almond Board: “AF36, Biocontrol Agent for Aflatoxins, Now Approved for Almonds.”

    5. Aim for Timely Harvest

    Growers should keep in mind that a third-generation NOW flight poses one of the greatest threats to the orchard around harvest time, so almonds should be harvested as soon as possible. Timely harvest is when there is 95–100% hullsplit at eye level in the canopy and will avoid NOW infestations and subsequent aflatoxin contamination. Early-harvested varieties, such as Nonpareil, are much less likely to attract egg laying once they’re on the ground, reducing the risk to later harvest varieties remaining in the trees.

    Click here to learn more about NOW control and management strategies. More details on SDI and other irrigation best practices may be found in the Almond Board’s Almond Irrigation Improvement Continuum. You can download a free copy of the Continuum at Almonds.com/Irrigation.  — By the Almond Board of California

  • YOU KNOW WHAT HULLSPLIT MEANS: IT’S TIME TO SPRAY

    Almond experts say there is only one proven way to know when hullsplit begins: inspect your trees from the top down, starting in the southwest corner of the canopy.
    The importance of knowing precisely when hullsplit occurs is critical because it signals the proper timing for treatments to control Navel Orangeworm (NOW). Whether growers use a ladder, climb into a pruning tower or lop off a few high branches with extension pruners, the goal is to understand what’s happening in the top of the tree, where nuts mature at a faster rate.

    Simply looking up into a tree’s canopy from the orchard floor is a sure way to miss the advent of hullsplit. When hulls split, a scent is released into the air, attracting female NOW moths to lay their eggs on the suture of the splitting hull. As the hull splits, fungal spores also can enter and spawn hull rot infections.

    Missing the beginning of hullsplit and allowing NOW or pathogens to gain a toehold in an orchard can wreck a grower’s entire season and reduce the value of the crop, costing growers in returns if nuts are rejected after harvest..

    Summer split invites unwanted guests 

    Growers can determine if hullsplit has occurred – and if it’s time to spray – if, when they squeeze the end of the hull, the entire suture opens up, exposing the shell within.

    Almond hulls split as the fruit ripens, and timing varies based on weather conditions and variety. For instance, the variety Nonpariel typically splits in early- to- mid-July, earlier than some other varieties.

    In addition, Director of Member Services for Blue Diamond Growers Mel Machado advises growers to look for blank nuts – those without a kernel inside – as those hulls are the first to split, several days ahead of the “sound” nuts (those with a full kernel).

    “The blanks are like the warning shot, signaling the start of hullsplit,” he said. “When full hullsplit does occur, the nuts at the top of the canopy will open up first.”

    Experts say growers also should pay attention to trees on the edge of their orchards as they often ripen more quickly.

    ‘Better to be too early than late’ 

    Once growers identify hullsplit in their orchard, their next step should be to initiate timely treatment. Experts warn that waiting too long to begin spraying will cost growers, as will performing a poor spray job.

    Machado advised, “It’s better to be a bit on the early side than late” when spraying. Once hullsplit begins, he recommended the entire orchard be sprayed in five days or less. “If it takes 10 or 15 days, that’s too long,” he said.

    Planning ahead – especially for smaller growers who rely on custom applicators – is essential.

    “Watch your fields closely and be in contact with your operator early on,” Machado advised.

    In larger orchards, Machado advises growers consider starting with aerial sprays, recognizing that ground-based sprays don’t always provide complete coverage at the tops of the trees.

    “We’re seeing growers effectively incorporate aerial applications into their treatment programs for the first application in order to cover the acreage in a timely manner,” Machado said.

    The best time to spray is early in the morning or at dusk.

    “Do not spray in the heat of the day – your application will evaporate into thin air and you won’t get the material where it needs to go. That’s a waste of time and money, as you’re not only wasting spray material but you also won’t achieve the coverage necessary to combat crop damage,” Machado said.

    Finally, growers should ensure their ground-based sprayers are properly calibrated, the nozzles are unplugged and that air flow isn’t restricted. Once it’s time to spray, growers should remind applicators to drive no more than two mph through orchards to ensure optimum coverage and to drive down each row to ensure the trees are equally covered.

    “There are some guys who spray every other row, and that’s not a good idea,” Machado said. “There are two sides to the tree; you need to spray both of them.”

    Machado reinforced that hullsplit sprays offer the final chance to manage NOW populations before harvest. Still, these applications are only part of a coordinated, year-round, integrated pest management plan to combat NOW that also must include winter sanitation and mating disruption, both of which are performed earlier in the crop year. — By the Almond Board of California

  • Successful Hullsplit Requires Thoughtful Irrigation, Nutrient Management

    While the onset of hullsplit signals that harvest season is near, it also marks the start of an unwelcomed orchard guest: hull rot. Almond hulls are susceptible to hull rot fungi from the beginning of hullsplit until the hulls dry, which is typically a month long, though the period may vary depending on fertilization and irrigation. Successful hull rot control is based upon effective strategic deficit irrigation and nitrogen management.

    Strategic Deficit Irrigation

    Strategic Deficit Irrigation (SDI) is the practice of stressing almond trees at specific crop stages to reduce water use without impacting crop productivity. By managing SDI, growers can reduce hull rot by 60–90% and experience a more uniform hullsplit and earlier harvest. These factors may contribute to less crop damage from weather, late-season NOW flights and aflatoxin contamination.

    The target period for stressing trees is from the start of hullsplit through 90% hullsplit, a period of about two weeks. The most accurate way to implement SDI is to use a pressure chamber to track and maintain slight tree water stress levels, between -14 bars and -18 bars, depending on the weather. Watch a short video from the Almond Board of California (ABC) about how to use a pressure chamber here.

    Growers who do not rely on pressure chambers, particularly those with a history of hull rot and a visual baseline from which plant stress can be observed, may achieve similar results by irrigating at 50% of normal tree demand, using crop evapotranspiration (ETc) calculations during hullsplit. More information about this strategy is available at the UC Almond Doctor’s website.

    Hullsplit typically occurs at the beginning of July in the early growing seasons and spreads to later growing seasons accordingly. However, onset of hullsplit can vary according to orchard conditions, with stress levels varying based on soil type and other factors. In shallow soils where trees may dry quickly, growers should initiate stress when blanks start to split, usually about a week before the onset of hullsplit. On deeper, well-drained soils, it can take up to 20-to-30 days to reach mild-to-moderate stress levels. In this case, growers may want to use the UC Almond Hull Split Prediction Modelto determine when to initiate water stress. More information about the fundamentals of strategic deficit irrigation are explained in this short ABC video here.

    Nitrogen Management

    Almond Board-funded research has found that excessive nitrogen increases incidences of hull rot. It is critical that a proper nitrogen budgeting plan is in place for the growing season to ensure that only the necessary amount of nitrogen is applied. It is important to follow the nitrogen budgeting plan throughout the growing season, which is a function of crop load.