Soft Scale

Identification and Management of Soft Scale

Soft scales are aphid-like creatures that feed on the sap of trees. Immature scales, called crawlers feed on foliage whereas mature scales feed on branches. All soft scales feed on the sap contents of the tree which means they are susceptible to systemic insecticides. They also produce a lot of honeydew. Dormant oils and contact insecticides can be effective, but only if they are applied to the unprotected crawler stage of the scale. Thus, timing of contact insecticide application is critical to effective control.

Lecanium Scale

(Parthenolecanium spp)

Attacks: oaks, maples, ashes, and many other trees and shrubs

What you will see:

Scale are initially flattened and brown in appearance
Hardened and round when mature
Tip dieback in branches
Stunted chlorotic foliage
Premature leaf drop and branch dieback
Honeydew secretions on tops of branches
Black sooty mold growth on honeydew

Life cycle:

Overwinter as second instar nymphs on twigs
Scales mature in spring
Females lay eggs on twigs in May to June
Crawlers hatch in June and July
Crawlers migrate to the undersides of leaves to feed
In late summer, crawlers migrate back to the twigs to overwinter
One generation per year

Kermes Scale

(Allokermes spp)

Attacks: White oak and several other oak species

What you will see:

Adult females are approximately 1/4” in diameter
Yellow to tannish-colored balls with specks
Tip dieback in branches
Stunted chlorotic foliage
Premature leaf drop and branch dieback
Honeydew secretions on tops of branches
Black sooty mold growth on honeydew

Life cycle:

Females develop on the twigs
Males remain on the trunk and main branches
Eggs are deposited in July and hatch in September
Crawlers over-winter in cracks in bark
One generation per year

European Elm Scale

(Gossyparia spuria)

Attacks: Elms and Hackberry

What you will see:

Black lumps with white fuzz along the edges
Many scales in one location
Tip dieback in branches
Stunted chlorotic foliage
Premature leaf drop and branch dieback
Honeydew secretions on tops of branches
Black sooty mold growth on honeydew

Life cycle:

Over-winter as second instar nymphs in bark crevices
Females mature in late May, mate and begin laying eggs
Crawlers appear in late June
Egg hatch may extend through the end of July
Crawlers feed on leaves throughout the summer
Crawlers migrate to branches before the leaves drop in fall
One generation per year

Magnolia Scale

(Neolecanium cornuparvum)

Attacks: Magnolia

What you will see:

Big red and orange balls on the limbs
Adult female can measure up to 13mm
Small thin white scales all over green stem tissue (males)
Tip dieback in branches
Stunted chlorotic foliage
Premature leaf drop and branch dieback
Honeydew secretions on tops of branches
Black sooty mold growth on honeydew

Life cycle:

Overwinter as nymphs on one or two year old twigs
Nymphs mature in late June through early August
Males, small fly-like insects, emerge about the same time
Males mate with females and then die
Females give birth to live young, called crawlers, in late August or early September
Crawlers over-winter on young twigs
One generation per year in the Midwest