Magnolia Scale

Neolecanium cornuparvum

As its common name suggests, Magnolia scale, Neolecanium cornuparvum, is a frequent pest of magnolia species, including star magnolias, saucer magnolias, and cucumber tree. These large, easily seen insects cause damage to trees by attaching themselves to the tree’s vascular system and feeding on the sap. They can kill entire branches and weaken the tree. Branches are often black with mold that grows on the insects’ excrement, which is known as “honeydew”. This sticky ‘honeydew’ often covers objects under the tree, causing a nuisance.

Download Magnolia Scale Fact Sheet

Treatment Strategy

Treating magnolia scale requires persistence and several treatments. Typically, a mixture of sprayed treatments and soil-applied systemic insecticides will have the most success in controlling this pest. Once control is reached - usually in the first year - maintenance with soil-applied insecticides is required annually.

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Magnolia Scale Treatment Option 1

Early spring treatments with horticultural oil such as RTSA Horticultural Oil will be effective in controlling eggs by smothering them and breaking down the waxy coating they hide underneath. These applications should be timed with bud swell or leaf emergence. Follow up in June-August with a soil-applied systemic insecticide. This sprayed treatment only needs to occur in the first year of an infestation: subsequent treatments can be done with soil-applied systemic insecticides.

Application Type - Foliar spray

DIY Product/Equipment Needed:

•  RTSA Horticultural Oil

•  Pump up sprayer with wand

•  Gloves

•  Safety glasses

Magnolia Scale Treatment Option 2

In the summer, fast acting soil-applied products, such as Transtect, will be most effective against scales. Applied in June through August, Transtect™ will control feeding crawlers by moving through the tree exactly where the scales are feeding: its vascular system. This treatment needs to be applied every year in the summer to maintain protection from reinfestation.

Application Method - Soil drench or soil injection

DIY Equipment/Product Needed:

•  Transtect

•  Measuring or Diameter tape

•  Gloves

•  Soil Drench: Shovel and watering can or soil drench kit

•  Soil Injection: Soil injection kit

Magnolia Scale Treatment Option 3

Foliar sprays in late July with insecticides like Up-Star® Gold can kill the crawlers as they hatch and before they form their protective shell in August. Timing is difficult and sprays must be repeated at 2-week intervals from early August through mid September. Most professional arborists have moved to soil-applied treatments instead because of their longer residual and fewer concerns with non-target contact.

Application Type - Foliar spray

DIY Product/Equipment Needed:

•  Up-Star® Gold

•  Pump up sprayer with wand

•  Gloves

•  Safety glasses

Magnolia Scale DIY Kit

Option 1

Application TypeFoliar spray

DIY Product/Equipment Needed:

•  RTSA Horticultural Oil

•  Pump up sprayer with wand

•  Gloves

•  Safety glasses

Option 2

Application Method – Soil drench or soil injection

DIY Equipment/Product Needed:

•  Transtect

•  Measuring or Diameter tape

•  Gloves

•  Soil Drench: Shovel and watering can or soil drench kit

•  Soil Injection: Soil injection kit

Option 3

Application TypeFoliar spray

DIY Product/Equipment Needed:

•  Up-Star® Gold

•  Pump up sprayer with wand

•  Gloves

•  Safety glasses

How Is It Spread?

Magnolia scale produce one generation each year. Females produce eggs from mid-summer to fall. These eggs hatch in August through October. The young scale – known as crawlers – move to one- to two- year-old branches where they feed, grow a protective shell, and overwinter. Feeding resumes as leaves emerge the following spring, producing a large amount of honeydew. As summer approaches, the females lay eggs and then die, leaving behind their hollow brown shell that persists on the plant for months.

Susceptible Trees

Star magnolia, saucer magnolia, cucumber tree magnolia, lily magnolia, daphne spp., Virginia creeper, and tulip tree

Symptoms

• Sticky honeydew on leaves and items underneath the infested tree.

• Dwarfed or stunted growth on infested twigs.

• Branch decline on severely infested twigs.

Lookalikes

Other soft scale insects

Related/Similar Problems

Sooty mold

Timing

Spring Summer fall

Urgency

High

Risk of Spreading

High

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