California Almonds: Nut Drop Underway As Trees Adjust For Big Crop – AgFax

    Naval orange worm trap in an almond orchard. Photo: Sara Savary, AgFax Media

    • Here is this week’s issue of AgFax Tree Crops.
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    Owen Taylor, Editor
    Jenny Holtermann, Contributing Editor


    Warmer weather equals more insect and spider mite activity. As we slip into May, that is the trend across much of our coverage area.

    May sprays are cranking up or are in the planning stage.

    Almond nut drop has become more obvious. Trees are balancing their loads now, mostly shedding smaller nuts, our contacts tell us. Trees generally are still carrying a nice crop after the drop.

    Leaffooted plant bug is showing up at various infestation levels in places across our coverage area.

    Delayed leafout in some walnut orchards has caught the attention of PCAs and Extension personnel. The crop size still looks good.

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    Nick Groenenberg, Independent PCA, Hanford

    “The almond crop looks good this year, and our area seems to have a nice set.

    “Last week, growers combined sprays for mummies, mites and foliar nutrients. Historically, we have mite pressure, and with the weather growing hotter, navel orangeworm control is critical.

    “We’re finding cases where plant bugs have started stinging hulls. We haven’t found significant amounts of damage down to the nut, itself, and we haven’t found the insect. But the damage is there.

    “Several blocks of almonds started showing signs of phytophthora and warranted treatment. Growers are irrigating and fertilizing based on the orchard’s needs right now.

    “Pistachio nut set is looking good in our area. Mealybug sprays will begin in the second and third weeks of May. Plant bug materials will be included as necessary. Historically, mealybug pressure becomes evident over the next few weeks as the next generation is born.

    “We had good weather in our area for pistachio bloom — excellent pollination opportunities with the males and females pretty close together. Pistachio irrigation just started and fertilizer will begin shortly after that.

    “The wet weather earlier in the month led to weed growth in most crops.

    “Tomatoes, garlic and onions are all progressing well with no major insect problems as of yet.”


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

    “At the Nickels Soil Lab, we currently see nut drop in the later varieties. In Butte and Fritz, we’re finding significant drop of smaller sized nuts, which suggests they stopped growing several weeks ago.

    “To some degree, Independence as well as Monterey dropped some nuts earlier in the spring. Hopefully, this indicates an excessive nut set and the tree is naturally losing what it can’t feed. A fair number of nuts remain on the tree.

    “Irrigation continues and fertility programs are going strong.

    “Mummy sprays targeting the first generation of navel orangeworm have begun in the area. The first generation is a long flight, especially this year, and it started in some areas in the middle of March. However, with this warmer weather we see more eggs now.

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    “The forecast carries a 10% to 20% chance of showers over the weekend in the very northern part of the Sacramento Valley, but most forecasts don’t include rain in the southern Sacramento Valley. We are also looking at a shift to the mid-70s with this forecast, and the weather could be moving towards seasonable temperatures, at least in the short term.

    “Prune and peach growers are preparing to begin thinning, although some prune orchards don’t have enough of a crop to thin.

    “In walnuts, canopy development has been uneven in places, likely due to some combination of a warmer-than-normal February and early March and then a cooler weather pattern in late March and into early April.  Growers report delayed leafout and uneven nut development across the area.”


    Jhalendra Rijal, Area IPM Advisor, Northern San Joaquin Valley

    “Higher temperatures last week and this week have increased bug activity. Navel orangeworm trap counts are higher, which isn’t surprising. We set our NOW egg biofix for mid-April, based on our regular monitoring in almond orchards. So, larvae will begin hatching in the last week of April, based on those 100-degree days after biofix.

    “Mummy sprays began this week in high-pressure areas. Keep in mind that a spray isn’t critical in areas with low potential pressure or where growers did a thorough job of winter sanitation. We always need to remember that winter mummy sanitation is the foundation of navel orangeworm control, and no spray program will fully replace that.

    “Codling moth activity has also increased in places. We set a mid-April biofix. We also are seeing increased leaffooted bug pressure. While nuts are small, close early-season monitoring is essential. That’s when leaffooted bugs can cause significant damage that results in nut abortion and drop.

    “Brown marmorated stink bugs emerge and move into orchards in the spring at the same time as leaffooted bug, and their numbers build as temperatures go up. Look for live bugs and damaged nuts in the almond trees on the edges. If you see stink bugs in traps in almonds, be proactive in terms of control.

    “We found some mite activity lately. It’s early in the season for that, but we aren’t seeing high levels that require treatments. However, it’s crucial to monitor. We often see sixspotted thrips in almonds from the beginning of spring, and they can control low-level mite populations. Avoid preventative miticide sprays because they can reduce populations of the predatory thrips that help hold down mite pressure. Follow UC’s mite sampling guidelines and treat only if needed.

    “This is an ideal time for ant activity surveys. We recommend using the UC IPM mite and ant sampling guidelines for your growing area.”


    Doug Elrich, PCA, Big Valley Ag Services, Gridley

    “We are currently scouting for peach twig borer shoot-strike damage, and we have been catching large numbers in our traps over the last few weeks. Young almonds are pushing a lot of new growth, so we will continue monitoring for damage.

    “Substantial nut drop has occurred in some varieties as the trees adjust for the crop set. We do see a good crop on the trees, even after nut drop.

    “With the nuts sizing rapidly, trees have been using a lot of water. Growers are adjusting their fertilizer programs in anticipation of the crop size. Last year at this time we were still dealing with rainy weather and heavy disease pressure. This year, growing conditions are more ideal and overall disease pressure has been low.

    “Plant bug damage has shown up in places and we continue to monitor for them. Peach twig borer and navel orangeworm pressure has been building with this recent round of unseasonably warm weather. Growers are preparing for upcoming mummy sprays.

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    “Leafout lagged in some orchards – particularly with Montereys – and blocks struggled to leaf out, even though the trees had set a good crop.

    “Most almond blocks received 1 to 2 bloom sprays and a post-petal-fall spray to control disease. Most of our rain this year came early, with no significant or long-term rain into April.

    “Walnuts set a decent crop, with some varieties showing more doubles and triples than singles. Growers have started their first fertilizer applications over the last couple of weeks. A lot of Chandler orchards are straggling on leafout, with delayed budding, too.

    “Growers have been able to make one or two blight sprays in walnuts, which is fairly typical. We are approaching the spray timing for the first-generation 1A flight of codling moth, and we are catching large numbers of moths in our traps in certain areas.

    “We are monitoring for navel orangeworm in walnuts to gain an idea about pressure and life cycle patterns. NOW has been more of a problem in walnuts in recent years due to the increase in almond orchards in the area. Although damage is not a concern until husk split, we’re continuing to monitor them so we can assess the need to treat if the time comes. 

    “Foliar applications of zinc and other nutrients are going out. This is a good time to get zinc into the tree before leaves harden off. Some growers will apply zinc to the ground and others will spray an early application.

    “The prune crop appears fairly light, with some exceptions. Prunes thrive in wet and cool bloom conditions, but this year’s warm weather left us with a lighter-than-expected crop.”


    Aaron Beene, PCA, Simplot Grower Solutions, Merced

    “Overall, the almond crop looks heavy and clean, disease-wise. In orchards with three- to six-year-old trees, some primary branches are breaking due to heavy crops. Growers are topping and hedging to keep from losing large limbs. Even some trees that were tied are breaking at the rope from heavy branches.

    “We see traces of jacket rot and green fruit rot from the heavy rains earlier in the season. Mostly, the disease pressure is in the pollinators and persistent through the blocks.

    “We are checking historical hot spots for leaffooted plant bugs but haven’t found high populations. The nuts are starting to solidify and they will only be susceptible to damage for a few more weeks.

    “We did find stink bug in blocks near riparian areas. No signs of mites yet. However, mite pressure will likely increase as temperatures rise.

    “Growers are halfway through their nitrogen programs for the year. The remaining nitrogen applications will go out in May and June. Leaf sample collections will ensure that we’re meeting nutrient needs.

    “Mummy sprays will begin next week for navel orangeworm and peach twig borer. Depending on a block’s history, applications could include some combination of miticides, insecticides and fungicides. By mid-May, we probably will finish those applications.

    “Navel orangeworm trap counts have climbed over the past few weeks, and the bulk of egg laying and flights will likely occur in the first couple of weeks in May.

    “Nitrogen fertilizer applications started in pistachios last week. Nutrient foliar sprays will begin, as well. We continue to monitor for plant bugs.

    “Walnut size is progressing and we continue evaluating the growing crop. Nitrogen applications started, as well. In May, we will begin botryosphaeria sprays where needed. Codling moth pressure remains low.”

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