Agriculture: Spinach Pest Management Guidelines

Spinach Crown Mite

  • Rhizoglyphus sp.
  • Description of the Pest

    Spinach crown mites are tiny, almost transparent mites with prominent long hairs, or setae. They are soil and leaf dwelling. Above ground, they live deep in the crown of the spinach plant. Crown mite eggs are transparent and spherical and arelaid in the innermost parts of the plant. Immatures are similar to adults except smaller in size.

    Damage

    Crown mites may damage sprouting seeds, seedlings before or after emergence, or older plants. They feed primarily on newly expanding leaves at the heart of the plant. Their ability to injure the crop decreases as plants get larger and as plants grow rapidly. The damage appears as deformed leaves or as small holes in expanding leaves.

    Management

    Biological Control

    Numerous predatory mites prey on crown mites in the field. However, little effect is usually seen on crown mite populations.

    Cultural Control

    Crown mite damage is generally associated with soils that are high in organic matter and cool, wet conditions. Prompt destruction of harvested fields and good sanitation of fields before planting may reduce mite populations. Effectiveness of rotations with nonhost crops has not been studied.

    Organically Acceptable Methods

    Biological and cultural control and treatments with azadirachtin are acceptable for use on organically grown produce.

    Monitoring and Treatment Decisions

    Treat fields if damage is seen and cool, wet weather conditions exist.

    Common name Amount per acre** REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide‚Äôs properties and application timing. Always read the label of product being used.
     
    A. AZADIRACHTIN#
      (AZA-Direct) 1–2 pt 4 0
      (Neemix 4.5) 4–7 oz 12 0
      MODE OF ACTION GROUP NUMBER1: 18B
      COMMENTS: Provides marginal control of crown mites. In an organically certified crop, check with certifier for restrictions regarding the use of this product.
    ** Mix with enough water to provide complete coverage.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
    1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee).
    # Acceptable for use on organically grown produce.
    Text Updated: 12/09
    Treatment Table Updated: 12/09