Lecanium Scale

Fletcher scale, Terrapin scale, Hickory lecanium scale, Globose scale

Lecanium scale represents a group of common soft scales that infest a wide range of tree species. They attach themselves to the leaves and twigs of trees and shrubs and feed on the plant nutrients. Honeydew – the substance they excrete – is a nuisance, since it can coat objects underneath plants with a sticky sap. Feeding can cause significant damage to the host plant.

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Treatment Strategy

Treatment of Lecanium scale involves one application of an insecticide to the soil around the base of your tree each year.

Lecanium scale is most effectively treated with soil applied products such as Optrol™ and Transtect™. These systemic products are applied to the soil at the base of the tree and are taken up by the root system, working to control insects from the inside of the tree. A contact insecticide such as Up-Star® Gold or horticultural oil can be sprayed on the scales, but this is rarely used as the timing must coincide with crawler emergence.

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Lecanium Scale Treatment Option 1

Transtect is applied to the soil and will provide a quick knockdown (within 2 weeks). It has a residual of at least 90 days, and should be applied in the spring.

Application Type – Soil drench

DIY Product/Equipment Needed:

• Transtect

• Measuring or diameter tape

• Gloves

• Soil Drench: Bucket, watering can or soil drench kit

Lecanium Scale Treatment Option 2

Optrol™ is applied to the soil and has a long residual (1 year). However, it usually takes 30 – 60 days for the product to reach the leaves. Professional arborists often apply Optrol™ in the fall of the year for control the entire next season. Early spring applications are also very effective.

Application Type – Soil drench

DIY Product/Equipment Needed:

Optrol™

• Measuring or diameter tape

• Gloves

• Soil Drench: Bucket, watering can or soil drench kit

Lecanium Scale Treatment Option 3

Another option besides soil-applied insecticides is foliar sprays with horticultural oil or an insecticide, such as Up-Star® Gold. However, these applications need to be timed to coincide with egg hatch as the scale coatings protect the insect from these sprays at other times of the year.

Application Type – Foliar spray

DIY Product/Equipment Needed:

• Up-Star® Gold 

• RTSA Horticultural Oil

• Hand pump sprayer with wand

• Gloves

• Safety glasses

Lecanium Scale DIY Kit

Option 1

Application Type – Soil drench

DIY Product/Equipment Needed:

• Transtect

• Measuring or diameter tape

• Gloves

• Soil Drench: Bucket, watering can or soil drench kit

Option 2

Application Type – Soil drench

DIY Product/Equipment Needed:

Optrol™

• Measuring or diameter tape

• Gloves

• Soil Drench: Bucket, watering can or soil drench kit

Option 3

Application Type – Foliar spray

DIY Product/Equipment Needed:

• Up-Star® Gold 

• RTSA Horticultural Oil

• Hand pump sprayer with wand

• Gloves

• Safety glasses

How Is It Spread?

Lecanium scales overwinter on twigs and branches in their immature or nymphal stage. In the spring, they continue development and mature females produce large numbers of eggs. Baby crawlers emerge in late spring through early summer and migrate to the undersides of leaves where they feed until late summer. At this time they move back to the twigs to overwinter. There is one generation per year.

Susceptible Trees

Lecanium scales can be found on a wide range of trees including, but not limited to, oaks, maples, linden, and birch.

• Fletcher scale – arborvitae and yew

• Terrapin scale – maples and peach

• Hickory lecanium scale – hickory and elm

• Globose scale – stone fruits

Symptoms

Lecanium scales can cause twig dieback, stunted plant development, and premature leaf drop. The presence of sooty mold on the excreted honeydew may also give a blackened appearance to foliage and branches in severe cases. Ants, bees, and wasps may be attracted to the honeydew, and could be a clue to look for lecanium scales.

Lookalikes

Other soft scale insects

Related/Similar Problems

Sooty mold

Timing

Spring or Fall

Urgency

Moderate

Risk of Spreading

Moderate

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