| AFFECTING LEAVES: |
|
CONDITION |
CAUSE |
 |
Leaves
curled |
Large aspen tortrix (Choristoneura
conflictana)
|
|
Leaves
curled with tent of silk produced |
Western
tent caterpillar (Malacosoma fragilis)
|
|
No
curling or silk associated with injury |
Forest
tent caterpillar (Malacosoma disstria Hubner),
Redhumped
caterpillar (Schizura concinna),
Cottonwood leaf
beetle (Chrysomela scripta), or
Sawflies
(cimbidae)
|
|
Masses
of dark, spiney caterpillars on leaves |
Spiny elm caterpillar
[Mourning Cloak Butterfly] (Nymphalis antiopa) - No significant damage.
|
|
Leaves
spotted: Young leaves blackened |
Shoot blight (Venturia
tremulae) or Frost injury
|
|
Black
irregular spots on leaves |
Septoria leaf spot and
canker (Septoria populicola)
|
|
Dark
round spot which drops out of leaf, leaving shothole appearance |
Ink spot (Ciborinia
whetzelii)
|
|
Black
spots with yellow margins |
Marssonina
blight (Marssonina populi)
|
|
Rust or
orange colored spots |
Conifer-aspen rust (Melampspora
spp.)
|
|
Underside
spots with small depressions and patches of brown leaf hairs |
Eriophyid mites
|
|
Leaves
generally distorted or thickened; whole leaf or set of leaves so
distorted |
Poplar vagabond aphid (Erisomatidae
spp.)
|
|
Edge of
leaf folded into a series of ridges |
Eriophyid mites
|
|
Red,
thickened folds along leaf veins |
Gall midge
|
|
Leaves
with serpentine, silvery tunneling |
Aspen leafminer (Phyllocnistis
populiella)
|
|
Sucking
insects on leaves |
Clear-winged aspen aphid (Chaitophorus
populifoliae) or Leafhoppers
|
|
White
powdery material on upper or lower surface of leaf |
Powdery mildew (Erysiphe
cichoracearum)
|
|
Yellowed
leaves |
Root damage caused by
under or over watering or
Iron chlorosis
|
|
| AFFECTING TWIGS AND SMALLER BRANCHES: |
|
CONDITION |
CAUSE |
|
Twig
dieback; Shoot curled into a shepherd’s crook |
Shoot blight (Venturia
tremulae)
|
|
Meandering
tunnels under bark |
Flatheaded borer Agrilus
spp.
|
|
Twig
dieback with small pimple-like fruiting bodies (pycnidia) in the bark |
Cytospora canker (Valsa
spp., Leucostoma spp.)
|
|
Scales
on bark |
Oystershell scale (Lepidosaphes
ulmi)
|
|
| AFFECTING LARGER BRANCHES OR TRUNK: |
|
CONDITION |
CAUSE |
|
Areas of
dead bark, with discoloration and small pimple-like fruiting bodies
(pycnidia) |
Cytospora canker (Valsa
spp., Leucostoma spp.)
|
|
Small
(1/6 - in) gray or brown oystershell shaped objects on bark |
Oystershell scale (Lepidosaphes
ulmi)
|
|
Rounded
and often rough swellings on branches |
Aspen gall (Diplodia
tumefaciens)
|
|
Oozing
liquid from wounds with clear to white oozing or frothy malodorous
liquid |
Bacterial
wetwood/slimflux
|
|
Orange
staining ooze |
Poplar borer (Saperda
calcarata)
|
|
Cottony
growth on branches and/or trunk |
Woolly aphid (species
unknown)
|
|
Swellings
in branches or trunk |
Poplar
borer (Saperda calcarata)
|
|
Tunneling
with coarse sawdust often forced from opening |
Poplar borer (Saperda
calcarata)
|
|
Regular
rows of holes in trunk |
Sapsuckers
|
|
Open
wounds, internal decay, or swollen areas in stem |
Stem decay fungi (Phellinus
tremulae, Ganoderma applanatum, and other fungal genera)
|
|
Fungal
fruiting bodies (mushrooms, conks) present |
Stem decay fungi (Phellinus
tremulae, Ganoderma applanatum, and other fungal genera)
|
|
| AFFECTING ROOTS AND GROUND LINE AREA: |
|
CONDITION |
CAUSE |
|
White
root decay with white mycelial fans between bark and wood |
Armillaria root
disease (Armillaria mellea)
|
