Herbicides to control poisonous Pimelea species (Thymelaeaceae)

Pimelea poisoning is an ongoing, periodically serious problem for cattle producers in inland Australia. The annual native plants of the Thymelaeaceae family that cause the problem are widespread and animal management is currently the main means of minimizing poisoning. However, there are situations in the higher rainfall parts of the natural distribution area of these plants where farming and quite intensive property development do occur and here the use of selective herbicides may be an option. This research looked for herbicides that could be considered for registration for Pimelea control, bearing in mind the large potential costs involved if used over large areas.Group I hormone herbicides (for example 2,4-D) were quite effective as was metsulfuron-methyl and glyphosate at doses commonly registered for use on broad-leafed weeds. On the basis of minimizing costs and quickly suppressing seed-set, metsulfuron-methyl at 3.5–5 g a.i. ha−1 and 2,4-D at 375–500 g a.i. ha−1 were the most promising. Where medic (Medicago spp.) persistence is vital, 2,4-DB at 240–300 g a.i. ha−1 could be used and glyphosate at 1 kg a.i. ha−1 would be effective on fallowed ground if cost was not an over-riding concern.

► Herbaceous Pimelea species susceptible to 2,4-D, 2,4-DB and metsulfuron-methyl.
► Pimelea trichostachya and P. elongata sensitive to glyphosate.
► Effective herbicide use requires integration with other management actions.