Forest Pathology in New Zealand No. 12
(Third Edition 2010)
Algal and Fungal Leaf Spots* of Native Plants
I.A. Hood
(Revised by I.A. Hood)
* A selection of some of the more conspicuous leaf spots from among many found on native
plants. The first group in this leaflet are caused by green algae in the genus Cephaleuros and
the rest by microscopic fungi. Leaf spots produced by native rust fungi are described in leaflet
No. 14.
Cephaleuros algal leaf spot
Fig. 1 – Cephaleuros virescens
on Melicytus ramiflorus (mahoe).
Causal organisms
Cephaleuros lagerheimii Schmidle
C. minimus G. Karsten
C. parasiticus G. Karsten
C. virescens Kunze.
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic features
Greenish white, yellow, or reddish circular spots, up to 8 mm in diameter, slightly
raised with diffuse margins, on upper surfaces of green leaves (Fig. 1).
Brown spots sometimes present on lower leaf surfaces directly beneath those on
upper surfaces.
Hosts
Individual host
Cephaleuros sp.
Blechnum discolor
C. virescens
Brachyglottis repanda
C. virescens
Beilschmiedia tawa
C. parasiticus
Coprosma grandifolia
C. minimus; C. virescens
C. lucida
C. minimus
C. robusta
C. virescens
Corokia buddleioides
C. virescens
Dysoxylum spectabile
C. virescens
*Ficus elastica
C. virescens
Hedycarya arborea
C. virescens
Hoheria populnea
C. virescens
Knightia excelsa
C. minimus; C. parasiticus
*Laurus nobilis
C. virescens
*Ligustrum japonicum
C. virescens
Litsea calicaris
C. virescens
Macropiper excelsum
C. virescens
*Magnolia grandiflora
C. virescens
Melicope ternata
C. virescens
Melicytus macrophyllus
C. lagerheimii, C. virescens
M. ramiflorus
C. lagerheimii, C. virescens
Metrosideros excelsa
C. parasiticus
*Passiflora edulis
C. virescens
*Persea americana
C. virescens
Pseudowintera axillaris
C. virescens
Schleffera digitata
C. virescens
Vitex lucens
C. virescens
*Introduced host species
Distribution
C. parasiticus and C. virescens occur throughout New Zealand; C. lagerheimii is known
in the North Island and northern South Island; C. minimus is recorded in parts of the
North Island.
Disease development
These algae grow under the cuticle on the upper surface of the leaf, killing the tissue
beneath. Microscopic threads producing reproductive bodies eventually appear above
the leaf surface.
Economic importance
C. parasiticus and C. virescens cause disease in commercial crops in the tropics.
However, they are of no significance in New Zealand, where the infection is normally
harmless. Heavy attack may occasionally induce some defoliation of light-suppressed
plants. C. virescens is the most commonly seen species on leaves, notably of
M. ramiflorus (mahoe). Spots caused by C. minimus and C. parasiticus are very
common and conspicuous on leaves of K. excelsa (rewarewa).
Control
Not considered necessary.
Cercospora leaf spot of wineberry
Fig. 2 - Pseudocercospora aristoteliae
on Aristotelia serrata (wineberry).
Causal organism
Pseudocercospora aristoteliae (Cooke) Deighton
= Cercospora aristoteliae Cooke.
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic feature
Dark brown, circular spots, with yellow-brown margins, up to 12 mm in diameter,
coincident on both surfaces of green leaves (Fig. 2).
Host
Aristotelia serrata.
Distribution
Throughout New Zealand.
Disease development
The fungus produces microscopic, asexual spores which spread the infection to other
leaves.
Economic importance
Aristotelia serrata (wineberry) is a comparatively short-lived hardwood shrub that
regenerates vigorously on disturbed or cleared sites in native forests. It may become a
troublesome weed during the establishment and early growth of planted trees.
Pseudocercospora aristoteliae does not appear to have any potential as a biological
control agent of wineberry, as it has little, if any, effect on its host.
Control
Not considered necessary.
Corynelia leaf spot of podocarps
Causal organism
Corynelia tropica (Auerswald & Rabenhorst) Starbäck.
Type of injury
Spotting and disfigurement of green foliage.
Fig. 3 - Corynelia tropica fruiting
bodies on Podocarpus totara (totara).
Diagnostic features
Yellow or pink, oval spots (up to 4 mm long by 2 mm wide) between midribs and
margins of green needles, coincident on both leaf surfaces, and also on twigs and
fruits.
Prominent, black, coral-like fruiting bodies (up to 4 mm long by 1 mm wide) on
spots, mainly those on lower needle surfaces and on twigs (Fig. 3).
Hosts
Podocarpus acutifolius; P. hallii; P. nivalis; P. totara; P. hallii × nivalis;
P. hallii × totara.
Distribution
Throughout New Zealand at altitudes up to 1000 m above sea level.
Disease development
Spores infect new foliage only, but infection persists and can be found on 4- and 5-yearold needles. Fruiting bodies first appear between December and February on the new
foliage of seedlings and trees of all ages.
Economic importance
Of no significance. Corynelia tropica is generally harmless, but very heavy infections
may limit shoot growth and destroy fruits.
Control
Not considered necessary.
Diplochorella leaf spot of mahoe
Fig. 4 - Diplochorella colensoi on
Melicytus ramiflorus (mahoe).
Causal organism
Diplochorella colensoi (Berkeley) P.R. Johnston & P.F. Cannon
= Diplochorella melicyti (Sydow & P. Sydow) Sydow & P. Sydow).
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic feature
•
Black angular spots, up to 2 mm in diameter, coincident on both surfaces of green or
yellow leaves (Fig. 4).
Host
Melicytus ramiflorus.
Distribution
Through most of New Zealand (not recorded south of Canterbury).
Disease development
The fungus appears to cause premature yellowing of some foliage. Microscopic sexual
fruiting bodies are formed within the leaves and produce spores which infect other
leaves.
Economic importance
Of no significance.
Control
Not considered necessary.
Mycosphaerella leaf spot of coprosma
Fig. 5 - Mycosphaerella coacervata on
Coprosma grandifolia. Note minute,
black fruiting bodies.
Causal organism
Mycosphaerella coacervata Sydow.
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic features
Irregular shaped, grey spots with reddish margins, up to 10 mm across, coincident
on both surfaces of green leaves.
Tiny, black fruiting bodies, barely visible to the eye, scattered on the spots of both
leaf surfaces (Fig. 5).
Hosts
Coprosma foetidissima; C. grandifolia; C. lucida; C. robusta; C. tenuifolia.
Distribution
Common throughout New Zealand.
Disease development
Sexual spores are produced in microscopic fruiting bodies present on leaf spots. These
spores spread the infection to other leaves.
Economic significance
Of no significance.
Control
Not considered necessary.
Placosoma leaf spot of pseudopanax
Fig. 6 - Placosoma nothopanacis on
Pseudopanax arboreus (five-finger).
Causal organism
Placosoma nothopanacis Sydow.
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic feature
Slightly raised, black, circular "tar spots", up to 8 mm in diameter, sometimes
concentrically grooved, on upper surfaces of green leaves (Fig. 6).
Hosts
Pseudopanax arboreus; P. colensoi; Raukaua simplex; R. simplex var. sinclairii.
Distribution
Common through most of New Zealand (not recorded south of Canterbury).
Disease development
Sexual spores are released from microscopic fruiting bodies present on leaf spots.
These spores then infect other leaves.
Economic importance
Of no significance.
Control
Not considered necessary.
Trabutia tar-spot of southern beech
Fig. 7 - Trabutia nothofagi on
Nothofagus solandri var. cliffortioides
(mountain beech).
Causal organism
Trabutia nothofagi Sydow.
Type of injury
Spotting and disfigurement of green foliage.
Diagnostic feature
Tiny (up to 1.5 mm diameter), black, shiny, convex "tar spots" scattered on upper
or lower leaf surfaces (Fig. 7).
Hosts
Nothofagus fusca; N. solandri var cliffortioides; N. truncata.
Distribution
Throughout New Zealand.
Disease development
Microscopic fruiting bodies are formed on the "tar spots" and produce either sexual or
asexual spores. These spores then infect other leaves.
Economic importance
This fungus may cause premature leaf shedding, but is of little significance.
Control
Not considered necessary.
BIBLIOGRAPHY
Dingley, J. M. 1969: Records of plant diseases in New Zealand. New Zealand
Department of Scientific and Industrial Research Bulletin 192.
Gadgil, P.D. 2005: Fungi on trees and shrubs in New Zealand. Fungi of New Zealand
Volume 4. Fungal Diversity Research Series 16: 1-437.
Gilmour, J.W. 1966: The pathology of forest trees in New Zealand. The fungal, bacterial,
and algal pathogens. New Zealand Forest Service, Forest Research Institute Technical
Paper No. 48.
Johnston, P.R. 1999: Tar-spot fungi on Nothofagus in New Zealand – a preliminary
report. New Zealand Journal of Botany 37: 703-714.
Pennycook, S.R. 1989: Plant diseases recorded in New Zealand. Plant Diseases
Division, DSIR, Auckland. 3 volumes.
Thompson, R.H.; Wujek, D.E. 1997: Trentepohliales: Cephaleuros, Phycopeltis, and
Stomatochroon. Morphology, Taxonomy, and Ecology. Science Publishers, Inc., Enfield,
New Hampshire, USA. 149 pp.