Diseases, pathogens and parasites of Undaria pinnatifida

A mycoplasma-like organism (MLO) causes the "twisted frond disease" or “coiling-stunt
disease” in Saccharina japonica from China (e.g. Wang et al. 1983; Wu et al. 1983;
Tsukidate 1991).
Animals
A number of amphipods are known to bore in kelp stipes and hollow them, causing
considerable damage which may eventually lead to the death of the host. In Alaska and
California, Peramphithoe stypotrupetes infests stipes of Laminaria setchellii damaged by
gastropod grazing (Chess 1993). Also in California and Alaska, it occurs in Saccharina
dentigera, and in southern California it is found in Eisenia arborea and Pterygophora
californica (Conlan & Chess 1992), while Californian Macrocystis pyrifera populations are
infested by the related amphipod P. humeralis (Chess 1993). In Ireland, Alaria esculenta is
inhabited by Amphitholina cuniculus (Myers 1974; Chess 1993). In Japan, Saccharina
japonica is similarly affected by Ceinina japonica (Akaike et al. 2002).
Fungi
The ascomycete Phycomelaina laminariae causes the “stipe blotch disease” in laminarian
species from the north-western and north-eastern Atlantic. Its hyphae penetrate the surface of
Alaria esculenta, Saccharina latissima, S. longicruris and Laminaria digitata, leading to
necrotic tissue and reduced overall performance of the host thalli (Sutherland 1915b, c;
Kohlmeyer 1968; Kohlmeyer 1979; Schatz et al. 1979; Schatz 1980, 1983, 1984a, c; Goff &
Glasgow 1980; Porter & Farnham 1986a).
Several other ascomycete fungi attack members of the Laminariales: Pontogeneia erikae is a
parasite in Egregia menziesii from California (Kohlmeyer & Demoulin 1981), Sigmoidea
marina causes lesions in the surface of Saccharina latissima from Britain (Haythorn et al.
1980), Ophiobolus laminariae causes blackened patches on the stipes of Laminaria digitata in
Scotland (Sutherland 1915c), and in California Asteromyces cruciatus has been reported from
Egregia menziesii, however their relationship is uncertain (Nolan 1972).
Oomycetes have also been reported from members of the Laminariales in the north-western
and north-eastern Atlantic: Petersenia sp. causes damage to the stipes of Laminaria digitata,
Laminaria sp. and Saccharina longicrucis (Kohlmeyer 1968) and Pleotrachelus minutus
infects the apical hairs of Chorda filum in Sweden (Aleem 1952a).
In France Labyrinthomyxa sauvageaui infects Laminaria ochroleuca (Duboscq 1921). An
unknown hyphomycete causes contortion of the blade and blackening of the stipe in
Laminaria digitata in Maine, USA (Kohlmeyer 1968) and in Russia an undetermined fungus
has been isolated from farmed populations of Saccharina japonica (Zvereva 1998).
Other algae
Green algae are occasionally observed growing in kelps, however very little information is
available on their impact on the host species. Acrochaete repens, for example, grows in
Chorda filum from the North American east coast (O’Kelly et al. 2004), Canada (South 1968)
and from Denmark, Ireland and the Isle of Man in the north eastern Atlantic (South 1968;
Nielsen 1979). The related species A. geniculata infects kelps along the North American
Pacific coast, such as Egregia menziesii, Cymathere triplicata, Laminaria sinclairii,
Saccharina dentigera and Dictyoneurum californicum (O’Kelly 1983). Egregia menziesii
from British Columbia also hosts another Acrochaete species, A. apiculata (C. O’Kelly, pers.
com.).
The green endophyte Bolbocoleon piliferum is found on the east and west coast of the USA,
and eastern Canada, growing in the kelps Alaria marginata, Chorda filum, Cymathere
14 • Diseases, pathogens and parasites of Undaria pinnatifida MAF Biosecurity New Zealand