August Orchard Management Considerations for Almond and Walnut

It’s easy to miss important orchard tasks with the hustle and bustle of harvest. Use this list to keep on top of your management!

Almonds

  • Watch for rust in young orchards. Prevent early defoliation that can negatively affect flower bud formation for next. See the UC IPM rust guidelines for more information.
  • At harvest, collect nut samples for damage analysis. Grab them now and think about them later. Gather and freeze at least 100 nuts per orchard after shaking, but before sweeping. These samples will allow you to better understand damage results on your grade sheets and adapt IPM strategies for next year. Emily Symmes wrote about sampling and pest damage diagnosis last week.
  • If boron toxicity or deficiency is a concern, collect and submit hull samples at harvest for B analysis. For more information, see this post from The Almond Doctor.
  • Apply a last shot of nitrogen either shortly before or just after harvest to support bud development for next year. Generally, no more than 20% of the total season’s nitrogen should be applied between hull split and early post-harvest. Decreased planned application if July leaf levels were higher than 2.8% N. See the FREP guidelines for more on rate and timing of nitrogen applications.
  • Manage post-harvest irrigation to minimize water stress. Water stress in late August to early October can interfere with flower bud development for the following spring. Defoliation reduces tree vigor by reducing sugar production. This is particularly important for orchards with a long window between harvest of Nonpareil and late pollinizers.
  • Assess hull rot and shaker damage post-harvest. Hull rot symptoms can be found at the UC IPM website.

Walnut

  • Consider ethephon as a way to increase color quality and minimize the chances of multiple shakes in this low price year. Ethephon application should take place when 100% of sampled nuts have reached maturity, as indicated by “packing tissue brown” (PTB). This occurs around mid-August for the earliest varieties and around mid-September for Chandler in most years. See here for more on sampling to track PTB and ethephon application.
  • Monitor for Navel Orangeworm. Healthy, intact walnuts are only susceptible to NOW damage at and after hull split. Consult with your Pest Control Adviser or crop consultant for monitoring and treatment options, bearing in mind pre-harvest intervals, duration of residual activity, and impacts of materials to your overall IPM program. Reference these articles on navel orangeworm in walnuts and identification of navel orangeworm vs codling moth for more information.

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