Difficult to Diagnose Diseases - Integrated Plant Protection Center

Difficult to
Diagnose Diseases
Melodie Putnam
OSU Plant Clinic
Overview
• Arborvitae problems
–What is an arborvitae?
• Problem diseases, disorders
– What they look like
– How to distinguish between them
• “New” problems
Arborvitae:
Thuja plicata = western red cedar
Tall tree of native forests
Thuja occidentalis =
eastern arborvitae
- Common in landscapes, hedges
e.g. ‘Pyrimadalis’, ‘Emerald’
Thuja orientalis =
Platycladus orientalis, Oriental arborvitae
- Branches held vertically, parallel
Photos: C. Evans, P. Breen
Keithia blight
Photo: Pacific Forestry Center, Natural Resources Canada
Keithia blight
Large fruiting bodies in spring
Symptoms show year after
infection
Photo: J. Hopkins
Keithia blight
= Didymascella thujina (a fungus)
- only on Thuja plicata (W. red cedar)
- spores form on 1 yr old needles
Photo: J. Hopkins
Treatment:
-Cu, Bayleton, mancozeb, or Strike
during wet periods in spring
HOST
Berckmann’s blight
Berckmann’s blight
Berckmann’s blight
= Seimatosporium
Berckmansii (a fungus)
- esp. on Berckmann’s
arborvitae (Thuja orientalis
var. conspicua 'Berckmannsii‘)
- Thuja occidentalis ‘Pyramidalis’
not susceptible
HOST
Berckmann’s blight
- disease of small twigs
- spores formed in fall
Treatment:
- Cu in late Sept/early Oct &
in November
Pestalotiopsis
Photos: Robin Rosetta
Pestalotiopsis
Photos: Center of Food, Landuse
& Environmental Sciences, Weihenstephan
Pestalotiopsis
Photos: Robin Rosetta
Pestalotiopsis
= Pestalotiopsis funerea (a fungus)
- most common problem
- many species affected
- stress related problem
Treatment:
-Cu, Bordeaux
during wet periods in spring, early summer
Black flagging
Abiotic –
cause unknown
Black flagging
- cause unknown
- no treatment necessary
- prune to remove affected foliage
- encourage re-growth
Cypress tip moth = Argyresthia cupressella
Photo: Natural Resources Canada
Cypress tip moth
Photos: Robin Rosetta
Cypress tip moth
Photos: Robin Rosetta
Cypress tip moth
Use a broad-spectrum, persistent
insecticide timed to protect
new growth.
Phomopsis tip blight
Photo: E.L. Barnard
Phomopsis tip blight
Photo: D.J. Moorhead
Root rot
Photo: Cornell U.
Tip blight
Incense-cedar
Sphaeropsis (= Diplodia)
a fungus
Incense-cedar
Sphaeropsis (= Diplodia)
a fungus
Pondersoa pine
Sphaeropsis (= Diplodia)
Pondersoa pine
Sphaeropsis (= Diplodia)
Photo: K. Hillery
Sphaeropsis (= Diplodia)
Stress disease
- prune to remove inoculum
- reduce stress
- broad spectrum fungicides
from budbreak to shoot
elongation
e.g. chlorothalonil,
thiophanate-methyl,
propiconazole
Questions?
Photo: P. Breen