Pests image: European Elm Scale (EES)


European elm scale (EES) (Gossyparia Spuria) is a small, non-native soft scale insect that attacks all species of elm with American elm being the most susceptible. The scale also attacks hackberry trees. European elm scale is usually first noticed when honeydew produced by the female scales, and the associated black sooty mold that grows on the honeydew, become a nuisance on parked cars or outdoor furniture. The insect feeds on the branches and foliage of the tree causing premature foliage yellowing and leaf drop, branch and canopy dieback and, in heavy infestations, tree mortality.

Sign and Symptoms

Black lumps with white fuzz along the edges of the insect attached to twigs and branches create stunted, yellowing leaves leading to premature leaf drop and dieback. Undersized and sometimes yellow-mottled leaves form a thin crown in an elm and is a symptom of heavy feeding. Honeydew secretions on the top of branches creates black leaves, bark, sidewalks and other surfaces from black sooty mold growth.


Elm Tree

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We recommend monitoring European elm scale annually and treating nymphs (crawlers) once per season, as needed. Generally, treatments begin in early summer once crawlers are present. Refer to BioSIM maps as a guide for starting treatments.

BioForest performed an efficacy trial against European elm scale in Lethbridge, Alberta, in July 2014 using TreeAzin. A pre-treatment assessment was completed in June 2014, and a post-treatment assessment was completed in June 2015. Post-treatment assessments showed that scale populations per branch on the treated trees were reduced by 53% compared to the non-treated trees. This suggests that TreeAzin manages scale populations by inhibiting the growth of second instar nymphs into scales.

Featured Treatments



LALGUARD AZA is a water-soluble, botanical insecticide applied by microinjection into the active sapwood or used as a foliar spray on affected trees. The active ingredient, azadirachtin, is derived from the neem tree (Azadiracta indica), and is an extract of neem seeds (not neem oil). It is not a neonicotinoid nor is it from the aver...

Map EcoJect Microinjection System

EcoJect Microinjection System

The EcoJect Microinjection System is the world’s best tree injection tool kit. It’s easy to operate and maintain, and has rapid injection times. The EcoJect system features reusable canisters that load in seconds allowing you to inject multiple trees simultaneously, and no plugs are left in the trees. The kit comes in three sizes ...