May Prune Orchard Management Considerations

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

Updated by Clarissa Reyes, North Sacramento Valley Orchard System Staff Research Associate on February, 2023.

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.

  • Rust: Monitor for leaf rust beginning May 1. Treat at the first sign of rust. Effective materials for rust control are found at the UC IPM website in a free pdf. Scroll to the bottom of the page to find the link.
  • Peach twig borer (PTB): Monitor for PTB fruit feeding 400 degree days after the first biofix. In the orchard, look for larvae entry points on the fruit (ideally 15 fruit from 80 trees), especially where fruit contact each other or touch leaves. Treat if 2% or more (24+ of 1,200) of the fruit have damage.
  • Oblique-banded leaf roller (OBLR): Begin sampling fruit for OBLR damage 930 degree days after biofix. As with PTB, look for damage on fruit in the orchard (ideally 1,200) and treat if 2% or more have damage.
  • Irrigation: Continue irrigation monitoring to maintain adequate orchard moisture to avoid fruit damage (end cracking and/or sunburn).
  • Fertility: Continue with nitrogen and potassium fertilization program if a good crop is set. More than 50% of annual N budget should be applied before June 1st.
  • Aphids:┬áLeaf curl plum aphids move to summer hosts in May, but mealy plum aphid stay in orchards until mid-July. Heavy infestation of mealy plum aphid can limit flower bud development this year, which can mean less crop next year.


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