June Orchard Management Considerations

Franz Niederholzer, UCCE Orchard Advisor, Colusa, Sutter and Yuba Cos.
Katherine Jarvis-Shean, UCCE Orchard Advisor Yolo, Solano, & Sacramento Cos.
Luke Milliron, UCCE Orchard Advisor, Butte, Glenn and Tehama Cos.

June Orchard Management Considerations

  • Regulated Deficit Irrigation (RDI) induces, moderate water stress in the orchard to reduce Rhizopus hull rot and promote earlier, more even hull split. As my old high school driver ed teacher told us, slow down into turns. The orchard is turning towards harvest as hulls split. Ease off the “gas” of water and avoid nitrogen into this “turn” to manage hull rot and help hull split be more uniform. See the hull rot/irrigation article in this issue.
  • Get ready for hull split. Almonds become vulnerable to NOW feeding/damage once hull split begins. Closely monitor hull split in the upper SW side of Nonpareil (NP) trees on field edges as those exposed nuts usually split ahead of the rest of the orchard. Depending where you are in the Sacramento Valley and specific orchard conditions, hull split may start as early as late June or as late as mid-July. Consider an edge spray once sound nuts in the edge NP trees reach Stage 2C of hull split (see photo below). The rest of the NP in the orchard should follow in roughly a week. Depending on the pollinizer(s) used, growers and their PCAs should decide if the first hull split spray (at Stage 2C for NP) should be a full spray or just on the NP. See discussion in the NOW article in this newsletter.
  • Monitor for mites weekly in the orchard’s hot spots. Consider the presence of predators (sixspotted thrips and predator mites) in addition to the presence of spider mites when making treatment decisions. UC IPM guidelines use treatment thresholds of spider mite presence on 50% of leaves when predators are present, but only 30% of leaves if predators are absent. More on monitoring and treatment options here.
  • Timely harvest (100% hull split throughout the orchard) means less NOW risk. However, it also means longer drying times on the orchard floor and a higher chance for ant damage – if protein feeding ants are present. Survey ant colony concentration on the orchard floor 2 to 3 days after irrigation, counting active colonies in five 1,000 square foot areas (roughly a 5 x 6 tree rectangle). Confirm they are the undesirable (protein feeding) pavement or southern fire ants, not the harmless pyramid ants with the aid of these helpful photos. Estimate potential harvest damage using the table in the ant management article in this issue and proceed based on your damage tolerance.
  • Ground squirrels switch from eating green vegetation to seeds and grains in late May. This means that June is the beginning of the window in which they will eat baited rodenticides. Test bait acceptance before use of rodenticide to avoid toxin shyness. For more on ground squirrel management, see here.
  • Manage young tree irrigation carefully as summer heats up, especially with potted trees, to make sure water is wetting the rootzone. Find more on dealing with the challenge of irrigating potted trees here. Water sources (drippers and micro-sprinklers) should be moved away from the tree trunks after potted trees have been in the ground for a month.
Stage 2C of hull split. When sound nuts in the SW corner of tree tops look like this, this is THE critical timing for insecticide for navel orangeworm and fungicide for Rhizopus hull rot. When all the trees in the orchard have all the nuts that look at least like this from top to bottom, the orchard should be ready to harvest.

Stage 2C of hull split. When sound nuts in the SW corner of tree tops look like this, this is THE critical timing for insecticide for navel orangeworm and fungicide for Rhizopus hull rot. When all the trees in the orchard have all the nuts that look at least like this from top to bottom, the orchard should be ready to harvest.

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