Description of the Pest
The European fruit lecanium, also known as the brown apricot scale, occurs throughout California but is rarely a problem. This scale has one generation per year. It overwinters as a nymph on twigs and small branches. In spring, it grows rapidly and secretes large amounts of honeydew. The adult cover is domed, shiny brown, and about 0.25 inch (6 mm) in diameter with several ridges along the back. The females are parthenogenic (reproduce without being fertilized) and lay many eggs, filling the entire space beneath the covers. They die after egg production.
The European fruit lecanium sucks juices from leaves and twigs. Low to moderate numbers do not appear to be damaging, but high numbers reduce terminal growth and vigor. The chief injury is caused by the production of large amounts of honeydew; sooty mold growing on the honeydew can blacken areas on leaves and fruit.
Biological control is frequently effective. If treatment is needed, oil applied during dormancy or delayed dormancy is the most effective way to reduce numbers of this pest. It is also the least disruptive to biological control. However, some apricot cultivars are sensitive to dormant oil sprays. Crawlers (mobile first-instar nymphs) will die in hot weather (over 100°F).
Parasitic wasps play an important role in controlling this scale. The most important of these parasites are Coccophagus, Encyrtus, and Metaphycus spp. Parasitized nymphs are almost black and have convex covers; unparasitized nymphs are flat. Several parasites commonly emerge from a single parasitized adult scale, leaving a perforated cover. If parasite activity is hindered by ants tending and protecting the scales, take measures to control ants.
Organically Acceptable Methods
Biological control and some oil sprays are acceptable for use on organically grown apricots.
Monitoring and Treatment Decisions
Apply treatments during the dormant or delayed dormant period before rapid scale growth begins in early spring. High numbers of soft scales often result from the use of chemicals that are disruptive to parasites and predators. If a high degree of parasitization is observed, treatments may be delayed until late spring after crawlers emerge. Treat during the dormant or delayed dormant period if, during the previous year, scale populations or sooty mold were observed.
Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (example form— ).
|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||12||0|
|NARROW RANGE OIL#||4 gal||1.5 gal||12||0|
|MODE OF ACTION: Contact including smothering and barrier effects.|
|COMMENTS: Oil alone will control light to moderate numbers. Some of the new lower-chilling varieties, especially Poppycot, can be highly susceptible to oil damage. Use extreme care when applying oil to these varieties. Check with certifier to determine which products are organically acceptable.|
|MODE OF ACTION: Unknown. A botanical insecticide.|
|COMMENTS: Do not use Trilogy after pit hardening on stone fruit. Do not apply more than 5 gallons of Trilogy/acre per application.|
|(Centaur)||34.5 oz||8.625 oz||12||14|
|MODE-OF-ACTION GROUP NUMBER1: 16|
|COMMENTS: An insect growth regulator that is effective against nymphal stages. Apply when crawlers emerge. Good coverage is essential. Use allowed under a supplemental label. Do not apply more than 69 oz/acre per year.|
|(Admire Pro -soil application)||7–10.5 fl oz||12||21|
|MODE-OF-ACTION GROUP NUMBER1: 4A|
|COMMENTS: Do not apply prebloom. During bloom, do not apply directly or allow to drift onto blooming crops or weeds where bees are foraging. Do not apply more than 10.5 fl oz Admire Pro/acre (0.38 lb a.i./acre) per year.|
|**||For concentrate applications, use the amount given in 80 to 100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300 to 400 gal water/acre, according to label.|
|‡||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.|