Recent news about saffron thistle ('Carthamus lanatus L.')

Abstract

Saffron thistle ('Carthamus lanatus' L.) costs Australian agriculture around $111 million per annum, yet until recently, little was known about its population dynamics, how it could be managed in pastures or the potential for biological control. This paper discusses research that addressed these areas. Populations of saffron thistle vary between sites and years, largely in response to environmental conditions and pasture cover. Seed germination and seedling establishment is strongly affected by rainfall, pasture cover, seasonal cycles and seed density. Growth, development, survival and fecundity are strongly influenced by pasture competition and grazing. Seedbanks ranged from 800 to 2300 seeds M-2 in Australia and between 9 and 61 seeds m-² in southern France, within its native range. Grazing management techniques such as rotational grazing can reduce thistle density in pastures, mainly by increasing the amount of pasture cover in autumn, which reduces seedling emergence. There is one potential classical biological control agent, a crown-feeding fly 'Botanophila turcica', which appears to be specific to saffron thistle. The fly, however, has little impact on saffron thistle populations in its native range. Fungal pathogens with potential to be used in mycoherbicides have been identified in Australian pastures. Further research into saffron thistle taxonomy, potential distribution and biological control is required.