Hippodamia convergens and others
Ladybugs- Kind
- Wild — attract it
- Best for
- Wild scale-eating lady beetles give some natural control in late summer; conserve, do not buy
Pest
Magnolia scale
Neolecanium cornuparvum
The short answer
Magnolia scale is a soft scale that feeds only on magnolias. It is one of the largest scale insects in the US: mature females are about 1/2 inch (12 mm) across, smooth, pinkish-orange to brown and often coated in white wax. It sucks sap from the twigs and drips honeydew, which grows black sooty mould on the leaves and draws ants, wasps and yellowjackets. Heavy infestations thin the canopy, reduce flowering and kill branches. There is one generation a year. Spray horticultural oil on the overwintering nymphs in early spring, after freezing nights have passed and before the buds open. Spray again when crawlers appear in late summer.
Control it with
hero macro · adult females on a magnolia twig
Adult Neolecanium cornuparvum females on a magnolia twig. Photo: pending.
Identification
Adult females are 1/2 inch (12 mm) across: smooth, elliptical and domed, pinkish-orange to brown, and often covered in a white waxy coating or powder. They sit on one- and two-year-old twigs. Males become small, pink, gnat-like insects that can fly.
The overwintering nymphs are much smaller, dark grey with a red-brown ridge down the back, on the youngest twigs. They are easy to miss. If a magnolia was sticky last summer, look for them in winter, before an oil spray.
Easily confused with
- Parasitised scaleBeneficial — leave itA round exit hole in the scale's back, or a scale gone puffy or darker than its neighbours, means a parasitic wasp has already killed it. Leave it be.
Damage symptoms
The honeydew is usually noticed before the insects. Magnolia scale produces a lot of it: leaves, cars and paving under the tree turn sticky, then black with sooty mould, and Penn State notes that it attracts large numbers of ants, wasps and yellowjackets. The scale itself weakens the tree by drawing off sap. In heavy infestations Kentucky lists branch dieback, canopy thinning and possible death of the tree, and Penn State lists fewer leaves and flowers and twig and branch dieback.
- Sticky leaves, and sticky surfaces under the tree
- Black sooty mould on leaves and twigs
- Ants, wasps and yellowjackets visiting the twigs
- Thinner foliage and fewer flowers
- Discoloured twigs and dying branches
Lifecycle & degree days
One generation a year, in Pennsylvania, Kentucky and Minnesota. Nymphs overwinter on young twigs and mature through the summer. In Pennsylvania males emerge in late July to early August, and the females then give birth to live crawlers; Kentucky has males mating in early summer. Minnesota and Penn State put crawler emergence at late August to early September, while Kentucky starts it in July. The crawlers settle on young twigs and overwinter there. Minnesota warns that numbers can build rapidly within a single generation and advises treating in the same season the scales are seen.
- Generations / yr
- 1
- Overwinters
- Nymphs on 1–2-year-old twigs
- Crawlers
- Late Aug–early Sept (PA, MN); July–Aug (KY)
- Reproduction
- Live young (crawlers), not eggs
J
F
M
A
M
J
J
A
S
O
N
D
Host crops
Magnolia scale feeds only on magnolias. Penn State names star, cucumbertree, lily and saucer magnolias as preferred, and says it attacks other cultivars too, though less often. NC State describes star and lily magnolias as shrubs or small trees, so both host categories apply.
Monitoring & action thresholds
Action threshold
Sticky leaves or bumps on twigs
No numeric threshold is published. Minnesota warns that numbers can build rapidly within one generation and advises treating in the same season the scales are seen; choose the method by the season.
Check the twigs in winter for the small dark overwintering nymphs, and in summer for the large adults and for stickiness below the tree. Before crawlers are due (July in Kentucky, late August in Pennsylvania and Minnesota), wrap double-sided sticky tape around a few infested twigs and change it weekly. Crawlers show on it as tiny specks. UC IPM's general scale advice is to spray once crawler numbers on the tape have peaked and begun to fall.
Beneficial
Biological control
Penn State notes that larvae and adults of certain lady beetles give some natural control in late summer, and that pesticide sprays can interfere with it. Among the scale-eating lady beetles UC IPM describes is the twicestabbed lady beetle, Chilocorus orbus. Treat them as a help and not a cure. UC IPM calls parasitic wasps often the most important natural enemies of scales in general, but none of our sources gives parasitism figures for magnolia scale. Control ants tending the scales, because they drive off the predators and parasites. There is nothing worth buying. Oil sprays are the gentlest option for these predators. Broad-spectrum crawler sprays and systemics such as imidacloprid can harm them too.
Cultural controls
Oil is the backbone of magnolia scale control, and its timing is what makes it work. There are two windows a year.
- Dormant window: spray horticultural oil in early spring, after the danger of freezing nights has passed but before the buds open. It smothers the overwintering nymphs. Minnesota also suggests a late-autumn spray, but the Bonide label below limits autumn dormant sprays to a short list of trees that does not include magnolia, so check your label first
- Crawler window: spray again when crawlers are active, late July–September depending on the region; confirm with sticky tape
- Rates on one residential label (Bonide, EPA Reg. 4-80), for ornamental trees and shrubs: 5–7.5 tbsp per gallon for dormant sprays, 2–5 tbsp per gallon in summer. The label warns that drift and runoff may harm aquatic life. Follow your own product's label
- Do not spray oil below 40 °F or above 90 °F, on trees under drought stress, or where sulphur is on the foliage
- Wet every twig: oil kills only the scales it touches
- Prune out heavily infested twigs if they are confined to a few parts of a small tree
Chemical, last resort
Systemics such as imidacloprid move into flowers and can harm pollinators, so never apply them during or shortly before bloom; Kentucky times imidacloprid for May, after the petals fallCheck any product before it goes on. Open the compatibility matrix →
- Horticultural oilREI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
Penn State Extension, Magnolia Scale (G.A. Hoover, 2002)
UMN Extension, Scale insects on trees and shrubs (J. Hahn, reviewed 2021)
Univ. of Kentucky ENTFACT-431, Magnolia Scale (Larson & Townsend, rev. 3/26)
UC IPM Pest Notes 7408, Scales (Kabashima & Dreistadt, 2014)
Bonide Horticultural & Dormant Spray Oil label, EPA Reg. 4-80 (2024)
NC State Extension Plant Toolbox, Magnolia stellata and Magnolia liliiflora
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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