May 2020, Issue 6
Shelling Out Useful, Real-World Almond Knowledge

The time to start planning is now. Every month brings new needs and new possibilities to your orchard, so we’ve done our best to put together the following advice for your almonds.
COVID-19 Customer Update
Potassium Utilization at Bud Differentiation and its Role in Spur Fruitfulness

Potassium is an essential nutrient and, in almonds, it plays a key role in determining how many fruiting spurs will be produced for the following spring. Practical thinking suggests that post-harvest nutrition should be a driver for a strong bloom next year. While there is a benefit to putting your trees to bed with a strong post-harvest reserve of nutrients, if you wait until then to address potassium deficiencies, then it's too late. Bud differentiation in almonds occurs during August and September and trees have already “decided” which buds become leaves and which will bloom, long before the majority of growers apply post-harvest fertilizer.

Potassium has many essential roles in plants, the most important for bud differentiation is its role in carbohydrate reserves. Potassium is used for energy, movement, and storage, aiding in the transport of carbohydrates from leaves to developing fruit and buds (prior to bud differentiation and during the post-harvest window prior to leaf drop). By assisting in moving carbohydrates/energy into the buds, almond trees move into the dormant period with a full gas tank, ready to set a large crop the next year.
Potassium’s role in spur fruitfulness is well documented. Potassium-deficient trees have been shown to have lower levels of spur fruitfulness and spur survival. In one university research trial, a heavily cropped orchard with low potassium levels had a 10% increase in spur mortality compared to trees within the same orchard given adequate potassium. On top of fewer surviving spurs, the following year the potassium deficient trees had 8% less fruitful spurs; these spurs produced only leaves, no flowers.

These two factors combined for a 15% decrease in yield compared to the potassium sufficient trees. Thus, research has shown conclusively that sufficient in-season potassium fertilization has a major impact on next year's yield. UC guidelines recommend tissue levels above 1.6% potassium in June; 1.6% is an average of the entire orchard, with some areas being deficient and some areas being sufficient. At Wilbur-Ellis, we recommend a tissue level of 1.8-2%, leaving a cushion so that all areas in the orchard are above the 1.6% threshold.

"Potassium deficiency may reduce floral differentiation." "Effects of potassium deficiency are likely to be cumulative, especially pronounced following years of heavy cropping." The sensitivity of Yield Determinants to Potassium Deficiency in 'Nonpareil' Almond. Journal of Horticultural Science and Biotechnology (2004) 79 (6) 906-910.
Justin Burrows, Wilbur-Ellis Agronomist PCA
Potassium Reference Card
TILL-IT REKOIL is formulated to provide soluble potassium and sulfur while providing a net-neutral pH modification to soils when used over time. 

TILL-IT KOMPOUND is a 19% K, 6% S potassium acetate and KTS combination for UAN side-dress, In-furrow, and fertigated markets.

FOLI-GRO KILO is designed for foliar or soil applications that require a soluble, concentrated potassium with low buffering capacity and no soil pH modification, perfect for applications with sensitive plant protection products.             

FOLI-GRO HUMI-K is formulated using the highest soluble potassium source available and PURIC™ superior quality, low sediment humic acid.
Know Your Hull Rot

The term Hull Rot is a comprehensive term for multiple pathogens. It is important to know which pathogen you have to determine the best course of action. Rhizopus, Monilinia, Aspergillus, and Phomopsis are the pathogens known to cause hull rot. Each produces characteristic symptoms that help in properly diagnosing which pathogen is the causative agent in your orchard.
  1. Rhizopus
  2. Monilinia
  3. Aspergillus
  4. Phomopsis
Monilinia causes tan lesions outside of the hull.

Rhizopus causes black fuzzy mold in and around the hull. Both Monilinia and Rhizopus can be limited through good nitrogen and water management practices. Limiting nitrogen use up to May and leveraging water management to decrease humidity in the orchard, especially those outfitted with micro-sprinklers, are recommended practices. Many fungicides in the 3,11 FRAC can help ease infections during May spray to first hull split. MERIVON® is a 7/11 FRAC group fungicide that is currently the only product labeled for all four hull rot complexes and provides 35-54% total control.

Aspergillus is a newer pathogen in the hull rot realm. This pathogen causes a flat-tight black fuzz more compact and deeper in the hull than Rhizopus. A higher occurrence happens past the “Deep V” development stage, as it typically occurs far behind the split (as pictured). Not much is known on Aspergillus treatments. Dr. Themis Michailides has presented AF-36 for use in control on Aspergillus aflatoxin on almonds, seeing a 40% reduction by end of the study. Timing applications of 1-2 weeks before the hulls split has shown the best efficacy. 

Phomopsis hull rot is mostly ambiguous. It can be shown as a greyish mold with shriveled nuts and gumming. Disease is often seen during high rainfall years. Phomopsis hull rot attacks Sonora and Carmel varieties more aggressively. Orchards that use more than 250 pounds of N per year are also at higher risk. Nuts stuck on trees are also a symptom of hull rot infection, which also becomes a breeding ground for overwintering spores as well as overwintering NOW. Mummy nut sanitation is very important for both hull rot and NOW control.
Susceptibility is influenced by variety and vigor. The Non-Pareil variety seems to be more susceptible to hull rot strikes from Aspergillus, Monilinia, and Rhizopus than other varieties.

Brooks Craven, Wilbur-Ellis Agronomist PCA

Merivon® is a registered trademark of BASF.
Pull Your Cards to Identify Damage

As we near hull split, it is important to monitor for NOW activity and plan your hull split sprays. “May sprays” should have been applied around the last week of April to the first week of May. The focus now should be on upcoming hull split sprays.

The beginning of hull split should be declared when about 1% of the earliest variety in your field begin to split. This often means checking nuts on the South or West sides of a field, but also looking high into the top of the tree. It is important to remember that the border rows and tops of trees will split much earlier than nuts set lower on the tree and inside the orchard. Blank nuts will split approximately 1-2 weeks ahead of regular nuts, so keep an eye out for them as well.

Weather, nutrient and water stress all have an impact of hull split timing, so one should never use purely a calendar date to time hull split. Growers and PCA’s should begin looking for signs of hull split in mid-to-late June depending on their area. It is important to identify sandy or stressed areas of a field as those are likely to split first. It is equally important to use your own knowledge and history of your fields. The below photos illustrate the progression of hull split.

Once 1% hull split is determined, sprays should begin. Sprays should be completed in no more than seven days. Second sprays should begin about two weeks later. Coverage is vital for control of Navel Orange Worm and should not be sacrificed for speed. In some cases, this may require hiring a custom applicator to do some or all of your farm. Take a close look at how many spray rigs your operation requires to adequately cover your farm in a timely manner. Consult with your Wilbur Ellis representative to discuss hull split timing, proper insecticides, water volume and equipment requirement

Always remember, it is much better to be too early than to be too late!

Joe O'Gorman, Wilbur-Ellis Agronomist PCA
(Left) Two nuts pulled from the same field show different progression. The almond on the right was pulled from a border tree and is beginning to form a suture. The nut on the left was pulled from inside a field and has not started to form a suture. (Right) Different stages on the same Branch. “Deep V” stage on the bottom nut and hull split on the upper nut.
Ceres Imaging

Wilbur-Ellis has partnered with Ceres Imaging for 2020. From pest management and disease control to irrigation, lab, or nutrient management, we want our growers to use data to achieve their goals. Wilbur-Ellis agronomists can use this data from Ceres to provide timely and strong recommendations to our customers. 
Lindsey Vieira, Wilbur-Ellis Field Technology Specialist
To learn more about which products are right for you, visit, or contact your local Wilbur-Ellis PCA/Agronomist
Stay tuned for next month’s newsletter and remember,
You Can’t Win Them All, But You Can Win Your Almonds
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