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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Elm > Sticky substance on leaves

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Elm > Leaves > Sticky substance on leaves

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  • Image: Woolly Elm Aphid 1
  • Image: Woolly Elm Aphid 2
  • Image: Woolly Elm Aphid 3

Woolly Elm Aphid
Eriosoma americanum, E.lanigerium and E. rileyi

  • Produces honeydew from the aphid feeding, look for sooty mold on leaf surfaces or twigs
  • Severe infestation can twist and curl leaves; leaves can yellow; branches can dieback
  • Colonies on wood are covered by a white waxy or cottony material
  • Adults are dark colored (reddish, brown, purplish), tiny size (1/16 to 5/32 inch)
  • Preferred hosts are American and slippery elm
  • More information on Woolly Elm Aphid
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  • Image: European elm scale 1
  • Image: European elm scale 2
  • Image: European elm scale 2

European elm scale
Gossyparia spuria

  • Excrete honeydew so leaves and branches may be covered by sooty mold
  • Yellow leaves on lower branches
  • Heavy infestations cause premature leaf drop and dieback of branches
  • Dark gray oval body outlined by white wax
  • Found mainly on American and rock elm
  • More information on European elm scale

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