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UC Pest Management Guidelines


European fruit lecanium, Parthenolecanium corni, adult female scale on bark.

Plum

European Fruit Lecanium

Scientific name: Parthenolecanium corni

(Reviewed 5/06, updated 4/09)

In this Guideline:


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** R.E.I.+ P.H.I.+
(trade name) (conc.) (dilute) (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, impact on natural enemies and honey bees, and impact of timing on beneficials. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of 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* 50WP 3 lb 1 lb 24 21
  4EC 3 pt 1 lb 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.
  . . . or . . .
  CHLORPYRIFOS*
  (Lorsban) 4EC 2 pt 0.5 pt 4 days 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Apply chlorpyrifos only during dormant or delayed dormant period and do not allow meat or dairy animals to graze in treated orchards. 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. Available for use under a special local needs registration.
 
** 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.
* Permit required from county agricultural commissioner for purchase or use.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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 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). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Insects and Mites:
R. E. Rice, Kearney Agricultural Center, Parlier

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