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 inches 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.
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.
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.
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. If present, ants will interfere with biological control; note their presence when monitoring.
Organically Acceptable Methods
Biological control and certain oil sprays are organically acceptable methods.
Monitoring and Treatment Decisions
To determine if a dormant or delayed-dormant treatment is warranted, follow sampling and treatment threshold guidelines in DORMANT SHOOT SAMPLING. 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 during the following dormant season.
|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 and 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||12||0|
|NARROW RANGE OIL (440 or higher)#||4 gal||1.5 gal||12||0|
|MODE OF ACTION: Contact including smothering and barrier effects.|
|COMMENTS: Choose a narrow range oil with a 50% distillation point of 440 or higher for dormant season use. Always check with your certifier as to which oils are organically acceptable. Oil alone can control moderate populations of soft scales.|
|**||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.|
|#||Acceptable for use on organically grown produce.|
|‡||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.|