California Almonds – Adjusting For Heavy Rains, Heavy Crop – AgFax Tree Crops

    Almond orchard. ©Sara Savary, AgFax Media

    • Here is this week’s issue of AgFax Tree Crops.
    • Our thanks to BASF and its California team for sponsoring this coverage.
    • Got questions or comments? Let us know.
    Owen Taylor, Editor
    Jenny Holtermann, Contributing Editor


    Warm temperatures are in the forecast at least into early next week.

    Spider mites tend to build as temperatures increase, so scout closely for them and any predators that might be in the mix.

    Leaffooted bug has turned up, with numbers in places maybe running slightly more than average. While it’s rarely a widespread pest, leaffooted bug can inflict crop damage where populations build.

    Navel orangeworm counts have increased in parts of our coverage area, with warmer weather likely prompting more activity.

    A large crop still seems likely. Our contacts have been telling us that for several weeks, which continues to be the prevailing sentiment.

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    Franz Niederholzer, UC Farm Advisor, Colusa, Sutter and Yuba Counties

    “The talk of rain last weekend didn’t materialize significantly across the Sacramento Valley. No signs of disease pressure seemed to develop following the previous storms. With higher temperatures, trap counts are increasing, too.

    “High temperatures have run in the mid-80s across most of the Sacramento Valley this week, and the north wind brought along a warmer and drier atmosphere. The forecast calls for warm temperatures approaching the mid-90s until Tuesday next week, but the forecast says to expect a cooldown after that.

    “Warm spring weather accelerates mite activity. However, when cool temperatures follow warm temperatures – which happens often in the spring – that shift helps with biocontrol. With cooler temperatures, spider mite population grow more slowly, and beneficials feast on spider mites enough to provide control.

    “Generally, the orchards appear to be carrying a good crop. The question lingers: how large will it eventually be?

    “Monitor closely for leaffooted plant bug. They are a spotty problem but cause substantial damage when present.

    “Going into May, sample leaves. We need that nutrient analysis to plan fertilizer programs. Also, track soil moisture to avoid over-irrigating trees.

    “In walnuts, we’re approaching the start of our nitrogen fertility programs, and 25% of the annual nitrogen budget should be applied each month for the next four months – May through August. Chandlers and Howards are not entirely leafed out yet and are still working on leaf expansion. Warmer weather will help move that along.

    “As expected, we aren’t seeing a uniform prune set. Prunes are more susceptible to warm weather during bloom, and we went through several days with highs above 80 degrees. That appears to have hurt the crop set this year. Where orchards bloomed before warm temperatures developed, the set looks okay.”


    Dan Prentice, Prentice Ag Consulting, Bakersfield

    “We are finding diseases in almonds that we haven’t seen much of in a couple of decades. That list includes shot hole, botrytis, rust and alternaria. You can find symptoms of several of these diseases in multiple areas. However, the magnitude isn’t terrible just yet.

    “Growers did apply a fungicide after the big 4-inch rainstorm a couple of weeks ago and are gearing up for another application next week.

    “This appears to be a more substantial almond crop then initially thought, which could be adding to the increase in disease pressure. We are seeing high disease rates in dense clusters of nuts and also in places where the flower parts and jackets didn’t fall off. The clusters, combined with debris left in the trees, serves as a starting point for infection when coupled with high moisture from the rains.

    “In areas where the crop is more spread out across the tree, less disease pressure seems to have developed. Botrytis and shot hole will most likely be less of a concern into the summer. Alternaria and rust are showing up earlier than usual, which will be the primary concern as we progress into the growing season. The stagnant air and increasing temperatures create an ideal environment for disease.

    “We’ve sprayed for mites as we found increasing populations, and that seems to be working well. Leaffooted bug is spotty in areas, slightly more than normal. We are finding pressure in historical areas but also in places where the insect hasn’t turned up in the past. In most orchards, populations aren’t high enough to justify applications, but monitoring will be essential.

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    “Navel orangeworm egg counts are slightly below average for this point. We will continue assessing things as the weather warms up over the next 3 to 4 weeks. Typically, we don’t see high populations in wet and cool weather.

    “In pistachios, navel orangeworm counts were running high initially, then they leveled off. The rain came early enough that we do not see botrytis or other leaf diseases.

    “We are monitoring for plant bug past bloom as shells start to size.”


    Aaron Heinrich, Independent Crop Advisor, AgriWest Inc., Escalon

    “We deployed egg, pheromone and kairomone traps in almonds and have seen a sharp increase in navel orangeworm over the last week as temperatures increased. Several growers will apply a mummy spray over the last two weeks of April. We detected a large overwintering flight, so knocking down populations now will be essential for pest management at hull split.

    “Almond growers will be making their second or third applications of fertilizer over the next few weeks. Mostly, those are going out through irrigation, with a few using dry materials or liquid nitrogen followed with irrigation. 

    “We have found a few mites. Mostly, we are monitoring for leaffooted plant bug. Although we have not seen large numbers of leaffooted bugs yet, we know they are out there, and we will treat if necessary.

    “Almonds are shaping up like a mega crop and, so far, most orchards look very clean. Most growers made at least two or more fungicide sprays during bloom, along with a later treatment to protect against tissue disease.

    “In walnuts, the first flight of codling moth is increasing, and that trend will likely continue because the forecast for the Ripon area calls for highs into the 90-degree range into next week. We are 180-degree days from the biofix for codling moth in Modesto. Treatment for the first flight will be at 300-degree days, which will be the last week of April and into the first week of May.

    “We are finding fruit tree leafrollers in moderate levels across Stanislaus and San Joaquin Counties. Depending on treatment time, we may be able to combine applications to control first generation codling moth when we spray for leafrollers. Walnuts can generally sustain damage, but when levels rise above moderate and high amounts, the leafroller can feed on nutlets and cause a problem that justifies a treatment.

    “Frosted scale has shown up, with heavy populations in a couple of walnut blocks that were treated during delayed dormant timing. We are monitoring them closely with sticky tape for crawler emergence to determine if a follow up treatment will be necessary.

    “Growers are starting to fertilize walnuts, and irrigation will begin as temperatures continue to remain high. Growers have a variety of tools available for irrigation monitoring, like pressure bombs, soil moisture readers and tensiometers.”

    Nathan Stewart, PCA, AgVantage Consulting, Inc., Visalia

    “We’re into our May spray in almonds and are including a fungicide where we have seen alternaria in the past or in locations with historic pressure. Plus, we’re monitoring areas with dense canopies, low winds and standing water.

    “Sunday night through Monday (4/20), we received roughly half an inch of rain in the Corcoran and Tipton areas. Going from cold weather and rain showers to 85 degrees this week creates perfect condition for alternaria. Growers are being extra cautious and are keeping an eye out.

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    “We are starting to see leaffooted plant bug and stick bug. Navel orangeworm also has started increasing. How much navel orangeworms are building depends on mummy removal and orchard sanitization practices. Treatments are going out where necessary. Early rains appear to have slowed mite development.

    “Fields are drying out now and growers are carefully assessing irrigation needs. They are maintaining irrigation sets to ensure adequate soil moisture.

    “People are trying to catch up on fertilizer applications. Because of rain over the last few weeks, they weren’t irrigating, so that reduced the amount of opportunities to apply fertilizer. Now, growers are getting into an irrigation rotation. We try to finish all fertilizer applications by the last week of May to help subside any hull rot.

    “Pistachios on the west side are in bloom and we are starting to see a decent set. Overall, the pistachio crop appears very consistent and uniform from top to bottom throughout the valley. Potentially, this could be an outstanding crop.

    “Growers are starting to fertilize pistachios as they assess the crop in the next few weeks. Nutrition sprays are underway for bloom.

    “Treatments are going out for plant bugs where needed. We’re detecting sporadic stings in places, plus plant bug activity is increasing where growers are mowing.

    “In walnuts, growers with Tulares have completed their ReTain applications. Tulare is still progressing in bloom and Chandlers are beginning to open up. In a few Ivanhoe orchards, we’ve applied up to three blight sprays due to spring rains.

    “Growers are cautious about not over-irrigating at this stage in walnuts. However, irrigation sets have started in certain areas.”


    Kris E. Tollerup, IPM Cooperative Extension Advisor, Kearney AREC, Parlier

    “Start monitoring for ants and make sure that pest species are present before treating. Approximately ten ant species commonly occur in almond orchards, but only two of them are economically important pest species – southern fire ant and pavement ant.

    “Also, begin monitoring for spider mites. It’s best to follow the UCIPM guidelines and avoid applying a miticide strictly as a preventive spray. We understand why growers use a preventive strategy when they have a lot of ground to cover. However, studies show preventive sprays are not necessarily effective. Ideally, use yellow sticky cards to monitor for both spider mites and sixspotted thrips, which are a spider mite predator. Treat only when necessary.”

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