Magnolia scale
Neolecanium cornuparvum
| Type | Insect |
|---|---|
| When | Adults visible in summer; crawlers late August through September. |
| Pressure by region | Moderate: Northeast, Southeast, Midwest |
About
A native soft scale, about 1/2 inch across when grown, that is one of the largest scale insects in the US and feeds only on magnolias (Penn State). It is widespread in the eastern US and favors star, cucumbertree, lily and saucer magnolias.
Spotting it
Damage
Sap feeding cuts leaf and flower production and causes twig and branch dieback; heavy infestations can kill trees. The scales drip sticky honeydew that turns black with sooty mold and draws ants, wasps and yellowjackets (Penn State).
How to find it early
In summer look for large, smooth, pinkish-orange to brown bumps coated in white wax on the twigs, sticky leaves, black sooty mold and lots of wasps around the tree. Infested twigs may look swollen and purple (Penn State).
When
Adults visible in summer; crawlers late August through September.
Life cycle
One generation a year. Tiny dark gray nymphs spend winter on one- and two-year-old twigs, grow into adults by late July or August, and the females give birth to live crawlers in late August and September that settle on young twigs for winter (Penn State).
What to do, gentlest first
Start at the top. Sprays are a last step; always read and follow the product label.
Protect lady beetles Natural enemies
Some lady beetles eat magnolia scale and give some control in late summer; pesticide sprays can kill them (Penn State).
Dormant oil in early spring Organic spray
Spray horticultural oil in early spring, after freezing nights are over but before the buds open (Penn State).
Follow the label.
Crawler spray in late summer Conventional spray
From late August through September, when crawlers are out, spray a registered insecticide labeled for scale on magnolia (Penn State).
Spraying can kill the lady beetles that help. Follow the label.
Plants it goes after
Pressure by region
Penn State describes it as widely distributed in the eastern US; western ratings are estimates.
| Northeast | Moderate |
|---|---|
| Southeast | Moderate |
| South Central | Low |
| Midwest | Moderate |
| Great Plains | Low |
| Mountain West | Low |
| Southwest | Low |
| Pacific Northwest | Low |
| California | Low |
| Alaska | Low |
| Hawaii | Low |
Ratings come from extension sources where available; some are estimates, as noted above.
Sources
Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.