In Western Australia, where Stanley Bellgard is from, they call Phytophthora a “Biological Bulldozer”. Catchy name, isn’t it. And Phytophthora agathidicida(formerly, PTA), more widely referred to by New Zealanders as ‘kauri dieback’, is proving equally destructive. The pathogen has infected New Zealand’s kauri forests in the upper North Island, threatening the viability of the iconic taonga tree. Bellgard, and his colleagues at Landcare Research, have a unique connection to the dieback story; making the critical discovery that PTA is a new species to science. In 1972 a Phytophthora (putatively identified by IMI/CAB International as Phytophthora heveae) was linked to dead and dying kauri on Great Barrier Island. Symptoms included yellowing of foliage, canopy thinning and occasional tree death.
Alarms bells started to ring in 2006, when the late Ross Beever FRS, an esteemed Landcare Research scientist, identified Phytophthora ‘taxon Agathis’ in Trounson Kauri Park in Northland, and kauri forest west of Auckland. Beever’s discovery challenged the identification of P. heveae as the causative organism. The DNA barcode ITS–sequence of the isolate obtained from Great Barrier Island and those from the mainland were identical to another species P. castaneae – but there were many morphological traits of the kauri-pathogen that made it appear to be a different organism. Confirmation the kauri Phytophthora was a new species within Clade 5 of the genus came when Bellgard and his colleagues carried on Beever’s work and formally identified the Phytophthora organism asPhytophthora agathidicida – the “kauri-killing” Phytophthora.