Purple leaf sand cherry (Prunus cistena) are susceptible to a large number of potential insect and disease pests. One of those insect pests is the European fruit lecanium scale (Parthenolecanium corni) or EFS for short. This native, soft bodied scale insect primarily feeds on fruit trees, although other trees and shrubs, such as maples, can be affected. They can cause significant damage and susceptible trees and shrubs should be monitored regularly for their presence.
European Fruit Lecanium Scale Identification
Their appearance is quite variable dependent on the tree or shrub they are feeding on. Typically though mature females are globular, mottled, hardened and dark brown to reddish brown or yellowish brown in colour. They measure between 3-6 mm (1/8″ and 1/4″) and are sessile (immobile). The males are small gnat like flies and are smaller than the females, they may or may not be produced. The crawlers are mobile but wingless, oval in shape and quite small, measuring just over 1mm (3/64″) and initially white in colour but turn yellowish or salmon coloured as they mature. The nymphs are smaller than the adults and more flattened and oval in shape, typically yellowish brown to dark brown.
As a soft bodied scale they produce honeydew (a sticky substance which is emitted as a result of their feeding). This honeydew attracts ants and wasps and black sooty mold can grow on it. Areas under trees or shrubs infested with these scales are often sticky.
European Fruit Lecanium Scale Life Cycle
The scale insects overwinter as nymphs in crevices on the host trees branches and twigs. In early spring the females mature and either mate or reproduce by parthenogenesis, (eggs develop and hatch without fertilization). The eggs are laid under the protective scale of the impregnated female and begin hatching in June, hatching can continue until Oct.. The crawlers leave the mother and crawl out to the leaves to feed. They shed their skin once and then in early fall they crawl back to the branches and prepare to settle in for the winter. There is one generation per year.
European Fruit Lecanium Scale Control
Biological control: lace wings, lady beetles, minute pirate bugs and parasitic wasps.
Manual control: The scale insects can be wiped off with a rag or tooth brush.
Sprays: Insecticidal soap can be used to help control the crawler stage.
:Dormant oil sprays can be applied during dormancy to suffocate overwintering nymphs.
Chemicals: For regions permitted the use of chemicals a systemic soil drench or trunk injection of imidacloprid (such as Merit) is effective. There are also foliar sprays available such as carbaryl or phyrethroids, they are applied at the crawler stage.
Photo Credits: all photos taken by the author.
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