How to Manage Pests
UC Pest Management Guidelines
European Fruit Lecanium
Scientific Name: Parthenolecanium corni
(Reviewed 11/09, updated 11/09, pesticides updated 9/15, corrected 1/19)
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 a 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 in diameter with several ridges along the back. In late spring females lay many eggs that fill the entire space beneath the covers; after the eggs are produced, they die.
The European fruit lecanium sucks juices from leaves and twigs. Low to moderate populations apparently are not damaging, but heavy populations reduce terminal growth and vigor. The chief injury is the production of large amounts of honeydew. Sooty mold growing on 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 the most effective way to reduce populations of this pest and the least disruptive of biological control.
Many natural enemies help to control populations of European fruit lecanium. Common predators include lady beetles (Chilocorus orbus, Hyperaspis spp., Rhyzobius lophanthae), lacewings, the predaceous sap beetle (Cybocephalus californicus) and predatory seed bugs (Phytocoris spp.). Parasites include Aphytis spp., Coccophagus spp., Encarsia spp., and Metaphycus spp. Frequently, scales found during the growing season are heavily parasitized.
Monitoring and Treatment Decisions
Populations of European fruit lecanium can be controlled with oil in the dormant season or in summer. Additional pesticides are necessary only when populations are severe. High scale populations 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. Crawler emergence can be monitored with the use of sticky tape wrapped around tree branches where populations are active. Examine sticky tape weekly for evidence of tiny yellow nymphs.
Treat during delayed-dormant period if scale population or sooty mold was observed the previous year.
UC IPM Pest Management Guidelines:
Insects and Mites
J. A. Grant, UC Cooperative Extension, San Joaquin County
Acknowledgment for contributions to Insects and Mites:J. Colyn, Mid-Valley Ag. Services
M. Devencenzi, Devencenzi Ag. Pest Mgmt. and Research
P. McKenzie, Mid-Valley Ag. Services