How to Choose the Right Hull Split Spray for Almonds

In a  bulletin from the Almond Board of California (ABC), the organization offers tips for growers to choose navel Orangeworm (NOW) hull split sprays.

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With final harvest preparations top of mind, growers may be considering spray applications to continue keeping navel orangeworm (NOW) at bay and protect their crop. Growers should work with their Pest Control Adviser (PCA) to determine if sprays are necessary based on trap monitoring along with flight calculations based on egg traps. Effective hull split sprays are difficult in order for good control to occur the material needs to reach the sutures of the nuts, and hull split can take 3 to 4 weeks to complete in a variety. Here’s a few things to keep in mind to improve the efficacy of hull split sprays a few things to keep in mind:

  1. Timing: Timing should coincide with the beginning of hull split and NOW’s second flight. The first spray should be completed at no later than 1% hull split. To predict the onset of hull split, reference the Almond Hull-Split Prediction Model created by Ted DeJong of UC Davis’ Plant Sciences Department.
  1. Chemistry: Assess the potential risks of the compound to beneficial organisms and environmental quality. NOW control should work in tandem with other IPM strategies, and some materials can decimate thrips that are working hard to control spider mites.
  1. Sprayer Calibration: Given the difficulty to reach the sutures of the nuts, take the time for ensure the sprayer is properly calibrated to effectively reach the tops of the trees.
  1. Volume: Growers and applicators should apply the proper volume of spray material to ensure full coverage. Consult a PCA to determine the correct volume, but research suggests 200 gallons per acre as a rule of thumb to maximize effectiveness.
  1. Speed: Research funded by ABC and others shows that proper sprayer speed and spray volume are often overlooked during hull split, even though research repeatedly shows slowing down improves coverage. Sprayer speeds should remain at the recommended 2 miles per hour to ensure better coverage.
  1. Repeat: Work with a PCA to assess any existing or potential crop damage after the first spray application to determine if another application is needed.