October Prune Orchard Management Considerations

Clarissa Reyes, North Sacramento Valley Orchard System Staff Research Associate

Please note that the following are general recommendations intended to help you keep track of regular practices in a busy time; the optimal timing for management practices may vary based on specific location and conditions.

  • Irrigation: Irrigate to maintain mild to moderate water stress post-harvest. Stem water potential should be between -12 and -16 bars as measured by a pressure chamber. Avoid high water stress levels as Cytospora spreads faster in stressed trees compared to adequately watered trees.
  • Salinity: Take soil samples to check soil salinity and toxic salt (chloride, sodium and/or boron) levels going into what could be a dry winter. This is especially important for newer orchards on Krymsk 86 rootstock, which is more sensitive to chloride than Marianna or Myro. UC ANR provides a free video series on soil sampling.
  • Zinc: Apply foliar zinc (Zn) to correct zinc deficiency (July leaf sample <18ppm). Spraying 20 lbs/acre of 36% zinc sulfate as natural leaf drop begins in late October can deliver needed zinc into the tree and, in addition, can facilitate leaf drop, reducing risk of blow over and/or disrupting aphid reproduction.
  • Cytospora: Prune to remove Cytospora and to manage next year’s crop.
    • Remove existing cytospora cankers and spore sources by cutting branches several inches to a foot below the symptoms and burn prunings (if permitted).
    • Consider your management goals: topping young vigorous trees before a big wind can reduce risk of blow-over, while long pruning can increase early yields in young prune plantings.
    • Prune early in the fall to allow cuts to harden off before seasonal rains. Protect fresh wounds from water-borne spores with a fungicide spray (Topsin-M® or Topsin-M® + Rally®).
  • Orchard Sanitation: Sanitize your orchard by removing fruit mummies and blighted shoots to remove disease inoculum. Remove bark damaged during harvest, and backhoe out diseased or dead trees to prepare for replants.


Leave a Reply

Your email address will not be published. Required fields are marked *