How to use the key
From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.
- Carefully examine the injury, noting any major symptoms or signs.
- Look under the appropriate headings in the key for the part of the tree and type of injury you are trying to identify.
- Compare the descriptions and illustrations with your observations.
Identification Key to Major Insects and Disease of Poplars
I. Injury to Cuttings or Seedlings
A. Failure of unrooted hardwood cuttings to flush or shoots quickly die.
1. Cuttings shriveled, blackened, with "pimple-like" structures on surface.
Blackstem
B. Shoots severed at soil surface.
1. Cuttings not blackened.
Variegated cutworm
II. Injury to Foliage
A. Leaves eaten.
1. Webbing present on branches.
a. Large webs (up to 3 feet in diameter).
Fall webworm
b. Small-large bags or tents.
Bagworm
Poplar tentmaker
2. No webbing present
Satin moth
Forest tent caterpillar
Viceroy butterfly
Grasshopper
Mourningcloak butterfly
Cottonwood leaf beetle
B. Leaves not eaten.
1. Young leaves withered, may droop, later turn black.
a. Generally present throughout trees in planting, no necrotic blotches on adjacent leaves.
Frost injury
b. Scattered or more prevalent on groups of trees, necrotic blotches on leaves.
Venturia leaf blight
Alternaria leaf blight
2. Leaves with large, irregular blotches, with or without concentric rings, usually not limited by
veins.
a. Large areas of leaves turn light brown in early summer, later dark brown-black "ink spots"
develop within affected area.
Ciborinia spot
b. Leaves in lower crown have brown-gray blotches and white concentric rings.
Septotinia leaf blotch
c. Leaves with brown to whitish-gray blotches and small black dots (fruit bodies) within.
Phyllosticta leaf blotch.
d. Leaves with patches of white-gray powder.
Powdery mildew
e. Leaves distorted, skeletonized.
Imported willow leaf beetle
Sarrothripus moth
f. Leaves with blisters, galls, or mined areas of various sizes and shapes.
Taphrina leaf blister
Leafminers
Gall insects
3. Leaves with small spots, often later coalescing into small, irregular blotches, generally limited
by veins.
a. Circular spots reddish with a chlorotic halo early in season, later turning dark brown, often
with a whitish raised center. Undersides of severely affected leaves bronze in color.
Marssonina leaf spot
b. Spots generally larger and more angular than above, occasionally irregularly shaped tan
blotch bordered by a dark brown margin.
Septoria leaf spot
c. Yellow-orange spots, later forming an orange powdery mass on undersides of leaves.
Melampsora leaf rust
4. Leaves misshapen, chlorotic, stunted.
a. Leaves with various mosaic or mottled chlorotic patterns.
Virus diseases
Leafhoppers
b. Leaves stunted, "burned" appearance.
Chemical injury
c. Leaves crinkled, missing on terminal shoots.
Cottonwood leafcurl mite.
d. Terminal shoots and leaves covered with colonies of aphids.
Brown aphid
Spotted poplar aphid
5. Leaves folded.
Leafcurl midge
6. Leaves tightly rolled.
Large aspen tortrix
III. Injury to Shoots
A. Elongating shoots injured in early spring.
1. Shoots curled, leaves wilted, terminals resemble a shepherd's crook.
a. Shoots and leaves black.
Venturia shoot blight
Frost
b. Shoots and leaves green or black, wilted.
Willowshoot sawfly
2. Frothy spittlemass on terminals.
Meadow spittlebug
3. Shoots swollen, irregular scars along shoots, dead or dying terminals.
Cottonwood twig borers
Tarnished plant bug
Southern clearwing moth
4. Large, irregular, green or brown galls on terminals.
Poplar vagabond aphid
B. Terminal shoots missing.
1. Small tree branches and shoots cleanly cut off near ground line.
Rabbit
2. Upper shoots of small trees nipped off, leaving a ragged end.
Deer
IV. Injury to Branches and Trunk
A. Bark removed or hanging in shreds on stems.
1. Bark hanging in shreds, no teeth marks on exposed wood.
Deer, elk, moose,
2. Bark not hanging in shreds, teeth marks on exposed wood.
Rodents
3. Bark split away, exposing wood at base of tree, usually on the southwest side.
Sunscald
B. Cracks, deformities, dieback, fruit bodies.
1. Depressed, dark central area often with cracks.
Septoria canker
2. Yellowish-orange areas, often with many raised pimple-like structures (fruit bodies). Bark
usually intact, often rough on older trees.
Cytospora, Dothichiza, Phomopsis,
3. Target-shaped rings of dead bark.
Miscellaneous cankers
4. Yellowish-orange to black, slightly depressed areas, blistering bark with gray pegs or gray
black cushion-like structures.
Hypoxylon canker
5. Hoof-shaped conks along upper stems of pole-size and larger trees.
White trunk rot
6. Slime flux originating from a wound or branch stub, running down side of trunk.
Wetwood
7. Tumor-like growth, warty appearance, large galls.
Agrobacterium
Bacterial canker
Miscellaneous stem deformities
8. Holes in bark with sap, wood shavings, and frass present.
Poplar borer
Poplar-and-willow borer
9. Tunneling at base of stem.
a. Sap flow and wood shavings present.
b.Swollen galleries encircling base.
Poplar clearwing moth
c. Frass in root collar and main roots.
Cottonwood borer
10. Slits on branches up to 3 inches long.
Cicada
Snowy tree cricket
11. White-brown crust on bark surface.
Scurfy scale
Oystershell scale
12. Branch and stem swellings.
a. Clumps of green plants present.
Mistletoe
b. Scars or holes present on swellings or galls.
Oberea branch borers
Bronze poplar borers
Poplar-gall spaerda
Gall insects
13. Root and butt rot.
Armillaria root rot
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