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.
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.
Signs & 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.
Tree at Risk: Elm Tree
Treatment Strategy
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.
After Treatment Expectations
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.