Australian Herbicide Resistance Initiative (AHRI) insight #110 - Behind every successful HWSC approach is crop competition
Australia
November 6, 2018
Harvest weed seed control (HWSC) is often described as the holy grail of weed management, but we all know how the saying “Behind every successful person…” ends. There are usually more factors at play than just the individual, whether that be lots of coffee or a great support team. The same goes for HWSC.
Research by Michael Walsh from the University of Sydney and John Broster from Charles Sturt University has shown that crop competition plays an important support role in the success of harvest weed seed control.
A survey of 71 wheat crops across Australia showed that the more competitive crops caused ryegrass to grow upright (seeking out light) and set seed higher in the crop canopy, where a greater proportion can be captured through HWSC.
When you consider that crop competition in its own right also reduces ryegrass seed production, it seems to be a support act punching above its weight.
But what happens over time? Does the ryegrass adapt to HWSC and become more prostrate or does it start to shed seed earlier?
A survey at nine of the locations where HWSC had been carried out for five or more years showed no clear evidence that ryegrass had ‘adapted’ compared with nearby sites with no history of HWSC. Although the potential for resistance to HWSC remains, it seems it may not occur readily in the field.