Know thy enemy – biology of our most problematic crop weeds with Dr Catherine Borger

These weeds cost growers $22.5 and $1.7 million per year, respectively. Understanding the ecology of these species is vital to developing a successful weed management plan.

A five-year GRDC project produced results on emergence patterns, seed bank persistence, seed shedding and competitive ability of great brome and barley grass, in Western Australia and South Australia (‘Seed bank ecology of emerging weeds’ UA00156).

The project found that three to four years seed set control was needed to remove a great brome or barley grass soil seed bank.

Great brome had high seed production in Western Australia and South Australia. Barley grass had much higher seed production in South Australia than Western Australia. Great brome grass and barley grass reduced crop yield, and in 2019, great brome at low to high densities reduced economic returns from a Mace wheat crop at Wongan Hills by $90-205/ha. Barley grass reduced economic returns of wheat by $67-138/ha.

Data on weed ecology and competitive ability was used to update a decision support tool; the Weed Seed Wizard (WSW).

The updated model was used to investigate harvest weed seed control (HWSC) as a potential management technique for great brome grass and barley grass.

The modelling indicated that harvest weed seed control is a valuable tool in the management of these species, even in the years where most weed seed is shed prior to harvest.

You can read Catherine’s paper here: Great brome and barley grass – modelling the long-term value of harvest weed seed control