| AFFECTING LEAVES: |
|
CONDITION
|
CAUSE
|
 |
Leaves
chewed |
Spiny elm caterpillar
(Nymphalis antiopa), Speckled green fruitworm (Orthosia
hibisci), Western
tent caterpillar (Malacossoma californicum), Fall webworm (Hyphantria
cunea), or Willow leaf beetle (Chrysomela aeneicollis)
|
|
Masses
of dark, spiny caterpillars on leaves |
Spiny elm caterpillar
(Nymphalis antiopa)
|
|
Leaves
with black spotting |
Tar spot (Rhytisma
salicinium)
|
|
Rust to
orange colored leaf spots |
Willow leaf rust
|
|
Leaves
with irregular raised pouch galls |
Eriophyid mite (Aculops
tetanothrix)
|
|
Leaves
skeletonized by beetle larvae |
Cottonwood leaf
beetle (Chrysomela scripta) or Willow leaf beetle (Chrysomela
aeneicollis)
|
|
Sticky
honeydew on leaves |
Black willow aphids (Pterocomma
smithiae) or Little green
and yellow willow aphids
|
|
White
powdery material on upper or lower surface of leaf |
Powdery mildew
|
|
| AFFECTING TWIGS AND SMALLER BRANCHES: |
|
CONDITION
|
CAUSE
|
|
Large
aphids on twigs |
Black willow aphids (Pterocomma
smithiae)
|
|
Scales |
Oystershell scale (Lepidosaphes
ulmi)
|
|
Cone-like
gall at end of twig |
Willow cone gall
midges (Phabdophaga strobiloides)
|
|
Large
beetles chewing bark |
Cottonwood borer (Plectodera
scalator)
|
|
Twigs
with closely spaced pimple-like fruiting bodies (pycnidia) |
Dothiora canker
|
|
| AFFECTING LARGER BRANCHES OR TRUNK: |
|
CONDITION
|
CAUSE
|
|
Tunneling
into wood |
Poplar and willow borer (Argrilus
difficilis), Flatheaded
appletree borer (Chrysobothris femorata), Cottonwood borer (Plectodera
scalator), or Bronze cane
borer and related species (Aprilus aurichalceus)
|
|
Areas of
dead bark with discoloration and small pimple-like fruiting bodies
(pycnidia) in the bark |
Cytospora canker (Valsa
spp., Leucostoma spp.)
|
|
Regular
rows of holes in trunk |
Sapsucker
|
|
Open
wounds, internal decay, swollen areas in stem |
Stem decay fungi (Collybia
velutipes, Phellinus igniarius and various fungal genera)
|
|
Fungal
fruiting bories (mushrooms, conks) present |
Stem decay fungi (Collybia
velutipes, Phellinus igniarius and various fungal genera)
|
|
Clear to
white oozing or frothy malodorous liquid exiting from wounds |
Bacterial wetwood and
slime flux
|
|
Visiting
oozing sap from trunk |
Flies (fruit flies
and other families)
|
