Soft Scales

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.

 
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Soft Scales

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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

Fletcher Scale
(Parthenolecanium fletcheri)

Attacks: Yew, arborvitae, and juniper
 
What you will see:
 
  • Big orange red balls on branches
  • Dead foliage
  • Honeydew
  • Black sooty mold
  • Adult scales at base of needles
  • Thin plants with crusts of sooty mold covering twigs

Life cycle:
 
  • Overwinter as second instar nymphs
  • Adults on the twigs start laying eggs in late May
  • Each female deposits 500—600 eggs
  • Egg hatch in June into oval yellow nymphs (crawlers)
  • Crawlers migrate a short distance to a new feeding site
  • Crawlers remain on host plant
  • One generation per growing season

Spruce Bud Scale
(Physokermes picea)
 
Attacks: Colorado, white, black, and Norway spruce
 
What you will see:
  • Adult scales are globular and reddish to dark brown
  • Located in clusters of 3 – 8 at the base of twigs
  • Scales look like tree buds
  • Lower branches are commonly infested
  • Heavy infestations will kill lower branches
  • Large amounts of honeydew on limbs below scales
  • Black sooty mold on honeydew drenched branches

Life cycle:
 
  • Overwinter as nymphs on under side of needles
  • In the spring females move onto the twigs
  • Nymphs mature to adults in April and May
  • Egg are formed under the adult female scale
  • Crawlers appear in mid June through early August
  • Crawlers settle on new growth to begin feeding
  • One generation per year

Cultural Management of Soft Scale

Cultural practices:
 
  • Enhance growing environment with the Root Enhancement System® with Mature Prescription Organic Matter
  • Fertilization should be low nitrogen
  • Chemical treatments are effective to control this problem insect. Please consult with your Arborist for the best therapies.