Why is the dormant/delayed dormant stage important in an IPM program?

Dormant bud of reproductive growth of almond.

Dormant spur

First swell stage of almond bloom.

Bud swell

Green tip stage of almond bloom.

Green tip

Dormancy is generally defined as the period from leaf fall until growth resumes in spring. Delayed dormancy is the period from the resumption of growth, indicated by bud swell, until green tip.

Dormant stage begins around December 1 and ends when bud growth begins, about February 1 or so. This crop stage varies according to region, variety, and weather.

The dormant stage is a critical period for certain pest management activities including:

  • Removing mummy nuts for management of navel orangeworm and brown rot.
  • Managing pests such as scales and mites with oil sprays. Sprays at this time of year are most effective because leaves are off trees allowing better coverage. Also, beneficial insects are less likely to be harmed.
  • Monitoring and assessing pest populations with the dormant spur sample.

Dormant versus delayed-dormant treatments

  • Pests best controlled with dormant treatment:
    • San Jose scale
  • Pests best controlled at delayed dormancy:
    • European red mites (eggs)
    • Brown mites (eggs)
    • Obliquebanded leafroller larvae in bud scales
  • Pests adequately controlled at either dormancy or delayed-dormancy:
    • European fruit lecanium nymphs
    • Peach twig borer larvae in hibernacula

Choice of insecticides

During the dormant stage, applications of organophosphate or pyrethroid insecticides against peach twig borer are discouraged in an IPM program. Delay peach twig borer Bt applications until bloom time.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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