European Fruit Lecanium
Parthenolecanium corni
7 host plants
Last updated
European fruit lecanium scale appears as hemispherical, brown bumps on branches and twigs of fruit trees, becoming most visible in late summer and fall. You will see scale insects that resemble small domes, grouped along twigs. Heavy infestations cause yellowing of foliage and branch dieback. Honeydew secretion attracts wasps and promotes sooty mold.
Apply horticultural oil in late dormancy before bud break to coat overwintering scales. Prune heavily infested branches if populations are light. Conserve parasitoid wasps and lady beetles. Maintain tree health through proper watering.
Quick Reference
European Fruit Lecanium Emergence (est.) typically begins around 3074 GDD₃₂. As of May 15, 2026, Puget Sound stations range from 1942.5 to 2137.2 GDD₃₂, approximately 937 units before the expected threshold.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 15, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,137 | Pre-season | Emergence (est.) | 937 |
| Kent / Auburn | 2,130 | Pre-season | Emergence (est.) | 944 |
| Seattle / UW | 2,102 | Pre-season | Emergence (est.) | 972 |
| Olympia / Tumwater | 2,064 | Pre-season | Emergence (est.) | 1,010 |
| Tacoma / Puyallup | 2,033 | Pre-season | Emergence (est.) | 1,042 |
| Bellingham / Whatcom | 2,012 | Pre-season | Emergence (est.) | 1,062 |
| Sequim / Rain Shadow | 1,943 | Pre-season | Emergence (est.) | 1,132 |
Source: UMD IPMnet, Pest GDD Catalog, Added 2026-04-03 About GDD₃₂ →
Cultural Controls
- Natural enemies such as ladybird beetles, green lacewings, and parasitic wasps help control scale populations.
- Avoid use of broad-spectrum insecticides which kill these and other beneficial insects.
- Control honeydew-feeding ants which may protect scales from predators.
- Hand-wipe to help control minor infestations.
- Prune and destroy heavily infested branches, when practical.