What is it?
European elm scale (EES) is a small soft scale that attacks elm trees, by sucking sap from branches and leaves. They hatch in late July and start feeding in mid-July, then overwinter on branches and twigs.
Symptoms
- Symptoms are usually not noticeable until the severe infestation.
- Leaf discoloration and premature leaf drop.
- Sparse canopy, twig and branch dieback.
- A sticky substance produced by female insects grows scooty mold, makes branches turn black.
Damages
- Heavy infestation may kill weakened trees and cause branch dieback in healthy trees.
- Make stains on items under the tree because of the “honeydew”.
What to do?
- Keep your tree healthy and strong can withstand pests and diseases attack.
- Pressure water the tree with water to hose down the insect.
- Apply dormant/horticultural oil to suffocate the pest.
- Only prune elm tree between October 1 and March 31 in Alberta.
- Introduce natural enemies such as parasitic wasps, predatory plant bugs.
- Apply insecticide by professional.
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