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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Deciduous Trees > Elm > Dots, spots or blotches on leaves

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Elm > Leaves > Dots, spots or blotches on leaves

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  • Image: Elm leafminer 1
  • Image: Elm leafminer 2
  • Image: Elm leafminer 3

Elm leafminer
Kaliofenusa ulmi

  • Feed inside leaves, first appearing as serpentine mines and gradually coalescing to give the appearance of brown blotch-like mines between leaf veins
  • Damaged leaves may remain on the tree throughout the growing season
  • Larvae are translucent white, legless, and are present inside leaves in late spring
  • Siberian and red elm are most commonly affected
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  • Image: Black spot 1
  • Image: Black spot 2
  • Image: Black spot 3

Black spot
Stegophora ulmea

  • Yellow spots on leaf surface with black dot later growing to black spot with a whitish border that is raised above leaf surface
  • Once black spots are numerous on a leaf, surrounding tissue eventually dies and turns brown
  • Earlier than normal defoliation if disease on tree is severe
  • Appears first on lower branches in wet seasons and progresses to higher branches
  • Damage is common late summer, early fall
  • All elms in Minnesota are hosts
  • More information on Black spot...
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  • Image: Powdery mildew 1
  • Image: Powdery mildew 2
  • Image: Powdery mildew 3

Powdery mildew
Phyllactinia guttata

  • White or gray powdery mats, resembling talcum powder, occur in spots, blotches or coat leaves
  • Lower shaded leaves are most commonly affected, common on small understory trees
  • Damage is common in spring or fall
  • More information on Powdery mildew...
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  • Image: Elm lace bug 1
  • Image: Elm lace bug 2
  • Image: Elm lace bug 3
  • - CLICK PHOTO TO ENLARGE -

Elm lace bug
Corythucha ulmi

  • Needle-like mouthparts cause white or yellow speckled or pinprick discolorations on leaves
  • Black dots or specks (droppings) are on the underside of leaves
  • Heavy feeding can cause severe discoloration and leaf drop
  • Lace bugs are 1/8 to 1/4 inch long; light colored bodies; intricate, lacy wings
  • Damage is most noticeable in mid to late summer
  • More information on Elm lace bug...
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  • Image: Sooty mold 1
  • Image: Sooty mold 2

Sooty mold

  • Black, brown, or gray soot-like covering on leaf surfaces, or twigs
  • Sticky, shiny secretions on leaves from sap-sucking insects (aphids, leaf hoppers, psyllids, etc.)
  • Insects or signs of insect damage (distorted, pin-prick feeding marks, etc.) may be seen on leaves above the worst affected moldy areas
  • More information on Sooty mold...
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  • Image: Elm casebearer 1
  • Image: Elm casebearer 2

Elm casebearer
Coleophora ulmifoliella

  • Larvae mine angular spots between leaf veins causing brown areas that can coalesce to complete browning in high infestations
  • Create cigar-shaped cases out of leaf tissue and silk that hang from leaf underside
  • Preferred hosts are American, red, and slippery elm
  • More information on Elm casebearer...

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