Poisonous Plants of the Genus Pimelea: A Menace for the Australian Livestock Industry

Abstract

Pimelea is a genus of about 140 plant species, some of which are well-known for causing animal poisoning resulting in significant economic losses to the Australian livestock industry. The main poisonous species/subspecies include Pimelea simplex (subsp. simplex and subsp. continua), P. trichostachya and P. elongata (generally referred to as Pimelea). These plants contain a diterpenoid orthoester toxin, called simplexin. Pimelea poisoning is known to cause the death of cattle (Bos taurus and B. indicus) or weaken surviving animals. Pimelea species are well-adapted native plants, and their diaspores (single seeded fruits) possess variable degrees of dormancy. Hence, the diaspores do not generally germinate in the same recruitment event, which makes management difficult, necessitating the development of integrated management strategies based on infestation circumstances (e.g., size and density). For example, the integration of herbicides with physical control techniques, competitive pasture establishment and tactical grazing could be effective in some situations. However, such options have not been widely adopted at the field level to mitigate ongoing management challenges. This systematic review provides a valuable synthesis of the current knowledge on the biology, ecology, and management of poisonous Pimelea species with a focus on the Australian livestock industry while identifying potential avenues for future research.

Keywords: Pimelea; animal toxicity; herbicides; simplexin; weed biology; weed management.

Figure 1

Distribution of the four poisonous Pimelea species across different States and Territories of Australia: (a) P. simplex subsp. simplex (b) P. simplex subsp. continua (c) P. trichostachya and (d) P. elongata in Australia. The data for maps were obtained from the Australasian Virtual Herbarium [13].

Figure 2

Pimelea plant species in field situations: (a) P. simplex subsp. simplex (b) P. trichostachya and (c) P. elongata [Source: Jenny Milson (a,b) and Richard Silcock (c) with permission].

Figure 3

Flower heads of (a) P. simplex subsp. simplex (b) P. trichostachya and (c) P. elongata (Source: Jenny Milson with permission).

Figure 4

A multi-faceted approach to manage poisonous Pimelea species in hospital paddocks. The integration of suitable individual tactics could result in sustainable management.