Agriculture: Plum 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 the most effective way to reduce populations of this pest and the least disruptive of biological control.

    Biological Control

    Fruit lecanium is frequently kept under control by parasitoids 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 acceptable in organically managed orchards.

    Monitoring and Treatment Decisions

    To determine if a dormant or delayed dormant treatment is warranted, see DORMANT SPUR SAMPLE. Look for parasitized scale during 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. Treatment is required only if 25% or more of spurs are infested with live, healthy scale. Generally oil alone is all that is 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 effect.
      COMMENTS: Oil alone can control moderate populations of soft scales and is all that is necessary if organophosphates are not required to manage other pests; for instance, if Bt is to be applied at bloom for peach twig borer. Oil applications at this time may cause some young shoots to burn or dieback, 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. Some varieties, especially those that are weak growers or low in vigor because of soil or other location-related issues, can be especially sensitive to oil. Not all oil products are organically acceptable; be sure to check individual products.
     
    B. DORMANT OIL such as:
      DORMANT FLOWABLE EMULSION 6 gal 1.5 gal 4 0
      NARROW RANGE OIL 4 gal 1 gal 4 0
      MODE OF ACTION: Contact including smothering and barrier effect.
      COMMENTS: Oil applications at this time may cause some young shoots to burn or dieback, 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. Some varieties, especially those that are weak growers or low in vigor because of soil or other location-related issues, can be especially sensitive to oil.
      . . . PLUS . . .(optional - add only for very high populations)
      DIAZINON*
      (Diazinon 50WP) 3 lb 1 lb 24 21
      (Diazinon 4EC) 3 pt 1 pt 24 21
      MODE OF ACTION GROUP NUMBER1: 1B
      COMMENTS: Levels in surface waters of this material that are high enough to be toxic to certain aquatic invertebrates have occurred following rains in January and February; avoid runoff into surface waters.
    * 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.
    1 Rotate insecticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers for insecticides and miticides (un=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
    Text Updated: 04/09
    Treatment Table Updated: 04/09