How to Manage Pests
UC Pest Management Guidelines
European Fruit Lecanium
Scientific name: Parthenolecanium corni
(Reviewed 10/14, updated 10/14)
In this Guideline:
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.
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— ).
UC IPM Pest Management Guidelines: Apricot
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
Acknowledgment for contributions to Insects and Mites:L. C. Hendricks, UC Cooperative Extension, Merced County
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