Diseases, pathogens and parasites of Undaria pinnatifida

Other algae
Laminariocolax aecidioides is an endophytic brown alga infecting farmed U. pinnatifida in
Japan (Akiyama 1977b; Yoshida & Akiyama 1978; Veiga et al. 1997). Infections result in
host thalli becoming thicker and stiffer, lowering their market value (Yoshida & Akiyama
1978).
3.2.3. Known pathogens in the introduced range other than New Zealand (Australia, UK,
France, Spain, USA (west coast), Argentina, Mexico, Taiwan)
The endophyte Laminariocolax aecidioides (as Gononema aecidioides) has been found in
farmed Undaria pinnatifida thalli from Spain (Veiga et al. 1997) and has also been found in
Undaria in Argentina (Gauna et al. pers. comm.).
3.2.4. Occurrence of known pathogens in New Zealand
Even though members of the genus Laminariocolax occur in New Zealand kelps, none have
so far been observed in Undaria pinnatifida. Instead, in New Zealand U. pinnatifida hosts
another endophyte, Microspongium tenuissimum, which is also found in Ecklonia radiata and
various red algae. The infection of U. pinnatifida with M. tenuissimum was not associated
with obvious macroscopic disease symptoms (Heesch 2005).
3.3. LAMINARIALES
3.3.1. Known pathogens worldwide
Viruses
There are no viral diseases reported from members of the Laminariales outside New Zealand
(see 3.2.2).
Bacteria
Most bacteria affecting kelps belong to the phylum Proteobacteria. Pathogenic species of
Alteromonas, Pseudoalteromonas, Pseudomonas and Vibrio have been recorded from
Saccharina japonica in China (e.g. Tang et al. 2001; Liu et al. 2002; Wang et al. 2006) and
Japan (e.g. Ezura et al. 1990; Yamada et al. 1990; Sawabe et al. 1998; Sawabe et al. 2000a, b;
Narita et al. 2001; Vairappan et al. 2001) resulting in holes and lesions on thalli and
eventually “rot disease”. Some proteobacteria indirectly affect gametophytes and young
sporophytes in culture when red spot disease of the culture bed (i.e. the culture ropes) causes
the young Saccharina japonica to detach from infected ropes (e.g. Ezura et al. 1988; Yumoto
et al. 1989a, b). Alteromonas sp. and Vibrio sp. are also associated with lesions and thallus
bleaching of Saccharina ochotensis and S. religiosa in Japan (Vairappan et al. 2001). A
species of Acinetobacter causes “white rot” in Nereocystis luetkeana resulting in rot of stipes
and pneumatocysts, which collapse and become covered in white slime within 7-10 days
(Andrews 1977).
In China, both the gametophytes and sporophytes of Saccharina japonica are prone to
“malformation disease” caused by the firmicute Macrococcus sp. (Anon. 1989).
Unspecified bacteria have been reported as pathogens in Macrocystis pyrifera, Pelagophycus
porra and Egregia laevigata in America (Brandt 1923), Saccharina japonica in China (Wu et
al. 1983; Ding 1992; Yang et al. 2001; Huang et al. 2002a, b). The “black rot” of Macrocystis
pyrifera in California is assumed to be caused by a unidentified parasitic microorganism
invading already damaged host thalli (Rheinheimer 1992).
MAF Biosecurity New Zealand Diseases, pathogens and parasites of Undaria pinnatifida • 13