THE first comprehensive in-paddock survey of summer weeds in WA is nearing release, with the area observed covering the entire grainbelt from north of Geraldton, down south and then east of Esperance.
Until now, only limited information has been available about in-paddock summer weed distribution and abundance in WA.
However, the two-year survey, which was completed over summer this year and made possible with investment from the Grain Research and Development Corporation (GRDC), will provide hard numbers for the entire Wheatbelt.
The survey was co-ordinated by Albany-based agronomist Andrew Storrie, of AGRONOMO, who spoke on the GRDC podcast about his work.
Mr Storrie said the early identification of summer weeds is very important if growers want to get good control.
"In the design, we've tried to make it as representative as possible so we've selected paddocks from the six major cropping zones and there's 197 paddocks being surveyed in total," Mr Storrie said.
"I had a recording sheet - I still used paper and pen - which was a transact with 52 points where I recorded what was present and took photos as I went.
"I didn't actually count each species, but at each of those 52 points on the transact I found what species were present, then when you added that up over the 52 points it provided the relative abundance."
The survey was set up in such a way that the disturbance to the grower was limited, however the farmers whose paddocks were involved did provide information in terms of what crops have been grown in the past and what their herbicide history is.
"Last summer, 2019/2020, the actual surveys were quite late in the season because of the way the rain occurred and because of that quite a few winter weeds were starting to germinate at that time," Mr Storrie said.
"As I started the survey in late November, we're not getting those winter seedlings, but what I did see was carry over of hard to kill weeds from the winter.
"However overall I saw very few grass weeds - I'm over halfway through the full survey and grass weeds certainly are not showing up much at this point."
In the 2020/21 summer, the main trends Mr Storrie witnessed was that flaxleaf fleabane tends to be moving north, while button grass was discovered west of Ravensthorpe, which was the first time the weed had been found that far south.
The other one that showed up further south was green mulla mulla, which had spread down roadsides and popped up in paddocks.
"You've also got species like feathertop rhodes grass that are spreading along roadsides because it's a surface germination and likes hard setting soils which are common on road shoulders," Mr Storrie said.
"It's certainly moving down laneways and roadways on farms, so growers need to be a little bit careful of that one, particularly if they don't have sheep."
When it comes to summer weed control, early identification is important particularly with increasing numbers of hard to control species and increasing levels of herbicide resistance.
"Getting on top of those weeds early makes them easier to control," Mr Storrie said.
"Grazing paddocks tend to have a higher range of species in them, as opposed to no-till paddocks, so stock in the systems in most cases is probably increasing weed issues rather than reducing them."
The full analysis of the survey is underway and Mr Storrie plans to get around to grower groups and meetings before harvest to share the data.
