| AFFECTING LEAVES: |
|
CONDITION |
CAUSE |
 |
Leaves
chewed |
Cottonwood leaf
beetle (Chrysomela scripta), Spiny elm caterpillar (Nymphalis
antiopa), Fall webworm
(Hyphantria cunea), or Tussock moth (Dasychira
vagans)
|
|
Webbing/Tents
produced |
Fall webworm (Hyphantria
canea), Western
tent caterpillar (Malacosoma californicum), or
Forest
tent caterpillar (Malacosoma disstria)
|
|
Small
holes chewed in leaves |
Flea beetles (Chrysomelidae)
|
|
Leaves
tunneled |
Aspen leafminer (Phyllocnistis
populiella)
|
|
Leaves
spotted with young leaves blackened |
Shoot blight (Venturia
populina) or Frost injury
|
|
Black
spots with yellow margins |
Marssonina
blight (Marssonina populi)
|
|
Black,
irregular spots |
Septoria leaf spot and
canker (Septoria popolicole)
|
|
Blackish-brown round spot, which drops out of leaf, leaving
shothole-like appearance |
Ink spot (Ciborinia
whetzelii)
|
|
Rust to
orange colored spots |
Conifer-aspen rust (Melampsora
spp.)
|
|
Yellowed
leaves |
Root damage caused by
under or over watering, or
Iron chlorosis
|
|
White
powdery material on upper or lower surface of leaves |
Powdery mildew (Erysiphe
cichoracerum)
|
|
Leaf
petioles, veins with swelling |
Petiole-gall aphids (Pemphigus
spp.)
|
|
Leaves
generally distorted and thickened |
Poplar vagabond aphid (Mordwilkoja
vagabunda)
|
|
| AFFECTING TWIGS AND SMALLER BRANCHES: |
|
CONDITION |
CAUSE |
|
Hollow
swellings on new shoots |
Petiole-gall aphids (Pemphigus
spp.)
|
|
Terminal
leaves distorted into thickened mass |
Poplar vagabond aphid (Mordwilkoja
vagabunda)
|
|
wigs
shredded in irregular row |
Cicada oviposition injury (Platypeisidae)
|
|
Swellings
in twigs, small branches |
Poplar gall borer (Superda inornata) or
Hail injury (upper surface only)
|
|
Scales
on twigs, branches |
Oystershell scale (Lepidosophes
ulmi)
|
|
Catkins
grossly distorted and enlarged |
Cottonwood catkin
gall mite (Eriophyes neoessigi)
|
|
| AFFECTING LARGER BRANCHES OR TRUNK: |
|
CONDITION |
CAUSE |
|
Fungal
fruiting bodies (mushrooms, conks) present |
Stem decay fungi
(various species)
|
|
Open
wounds, internal decay, swollen areas in stem |
Stem decay fungi
(various species)
|
|
Masses
of caterpillars resting on bark |
Forest
tent caterpillar (Malacosoma disstria)
|
|
Tunneling
in trunk, often with orange staining ooze |
Cottonwood borer (Plectodera
scalator), Poplar
borer (Saperda calcarata), Cottonwood Crown Borer, or
American hornet moth (Sesia tibialis)
|
|
Clear to
white oozing or frothy malodorous liquid exiting from wounds |
Bacterial wetwood/slime
flux
|
|
Areas of
dead bark with discoloration and small pimple-like fruiting bodies
(pycnidia) |
Cytospora canker (Valsa
spp., Leucostoma spp.)
|
|
Insects
visiting oozing sap from trunk |
Flies (various
families)
|
|
| AFFECTING ROOTS AND GROUND LINE AREA: |
|
CONDITION |
CAUSE |
|
White
root decay with white mycelial fans between bark and wood |
Armillaria root
disease (Armillaria mellea)
|
|
Gall at
ground line |
Crown gall (Agrobacterium
tumefaciens)
|
