Agriculture: Prune Pest Management Guidelines

European Fruit Lecanium

  • Parthenolecanium corni
  • Description of the Pest

    European fruit lecanium, also known as the brown apricot scale, occurs throughout the Central Valley, but is rarely a problem. The adult female's domed shell is shiny brown, about 0.4 inch in diameter. Eggs are laid in spring and hatch from May to July. The young develop through the remainder of the season and overwinter on twigs and small branches as partly grown crawlers. There is one generation each year.

    Damage

    The chief injury is the production of honeydew that, in large amounts, can damage leaves and fruit. Sooty mold growing in the honeydew can cause blackened areas on leaves and fruit.

    Management

    Biological control is frequently effective; if treatment is needed, oil applied during dormancy or delayed dormancy is an effective way to reduce populations of this pest and the least disruptive of natural enemies. Increased populations of this scale may appear when dormant sprays are omitted.

    Biological Control

    Fruit lecanium is frequently kept under control by parasites including Aphytis spp., Coccophagus spp., Encarsia spp., and Metaphycus spp. and predators including lady beetles and lacewings.

    Organically Acceptable Methods

    Biological control and oil sprays are organically acceptable methods.

    Monitoring and Treatment Decisions

    To determine if a dormant or delayed dormant treatment is warranted, see DORMANT SPUR SAMPLING. Record results on a monitoring form (PDF). Look for parasitized scale during the summer by lifting up scale covers as well as examining the covers for exit holes. If a large number of scales are parasitized, treatment may not be needed.

    Common name Amount to use** REI‡ PHI‡
    (Example trade name) (conc.) (dilute) (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's properties and application timing. Always read the label of the product being used.
     
    A. DORMANT OIL such as:
      DORMANT FLOWABLE EMULSION 6 gal 1–1.5 gal 4 0
      NARROW RANGE OIL# 4 gal 1.5 gal 4 0
      MODE OF ACTION: Contact including smothering and barrier effects.
      COMMENTS: Oil alone can control moderate populations of soft scales. Oil applications at this time may cause some young shoots to burn or die back, especially in years when trees are water-stressed, or have recently been subjected to freezing temperatures or to dry winds. Dormant flowable emulsion is less likely to cause burn. The Moyer variety is highly susceptible to oil injury; delaying the oil spray until late Feb. to March 1 will reduce oil burn. Not all oils are organically acceptable; be sure to check individual products.
    * Permit required from county agricultural commissioner for purchase or use.
    ** For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower if the label allows.
    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.
    # Acceptable for use on organically grown produce.

    Important Links

    Text Updated: 04/09
    Treatment Table Updated: 04/09
    Feedback