WITH the large number of canola varieties on the market and the breakdown of the Sylvestris gene for blackleg resistance, the decision of which canola variety to grow is a daunting one.
Several varieties were trialled by the Mingenew-Irwin Group at two sandplain farms to determine the best performers, and the results were surprising.
Carried out at Chris Eaton's farm north Mingenew and Peter Ward's farm at Yandanooka/Mingenew, both on yellow sand, the trials showed the best yielder was Trigold canola.
MIG trials coordinator Richard Quinlan said Trigold didn't appear to be a big vegetative crop, yet it produced the best figures.
"A downfall of Trigold is that it is not as vegetative as Surpass 501 and so is not as good at smothering out grass weeds as Surpass," he said.
"Farmers also need to be aware that while Trigold has multiple gene resistance to blackleg, it has a relatively low resistance rating of 4."
Stubby did not perform as well as Surpass 501 at the Ward site.
"In this year's trials, Stubby yielded 1.7t/ha compared with Surpass yielding 2.2t/ha," Mr Quinlan said.
"Stubby is also inherently low in oil, up to 4pc lower than Surpass 501.
"Stubby is much better suited to loamy soils rather than sand, so these trials did not really show it in its optimal growing conditions.
"On loams Stubby yields a lot better, as seen on the Greenough flats where it outyielded Surpass 501 this year.
"Surpass has a real niche position in the Mingenew area as a high-yielding canola variety and would be the best variety to grow, except it is very susceptible to the new blackleg strain."
Although there has been no reported outbreak of the new strain of blackleg, which overcomes the Silvestris resistance, Mr Quinlan is advising farmers to be cautious.
For anyone growing large areas of canola, it would be risky to continue growing canola varieties such as Surpass which have single-gene resistance, as blackleg could wipe out the entire canola crop.
"The onset of the new strain of blackleg takes Surpass 501's blackleg resistance rating from 9 to 1. It's simply not worth the risk," Mr Quinlan said.
Tornado 555 was another good performer in the MIG canola trials.
"Tornado is a long season canola which did surprisingly well in this year's dry growing season, yielding 2t/ha at Peter Ward's and 1.6t/ha at Chris Eaton's," Mr Quinlan said.
"It would appear that this canola has the capacity to vary its season length depending on when it is sown.
"Another bonus with Tornado 555 is its cabbage-like vegetative growth, meaning it is much more competitive with weeds. Tornado also has better blackleg resistance than Trigold, with a provisional blackleg rating of 6.5."
The Tranby variety showed it could yield well on sandy soil in a drier season.
"Tranby is a short season variety similar to Stubby. It yielded 1.9t/ha on yellow sand at Peter Ward's, while the highest yielding variety at that site was Trigold at 2.2t/ha," Mr Quinlan said.
The MIG trial also investigated the use of seed treatments on a range of canola varieties.
"For the past two years, our trial results have shown that there is no clear advantage of applying seed treatment to canola," he said.
"However this year's results show an increase of 200kg/ha in Stubby seed treated with Jockey compared with untreated seed.
"We did not see any differences in yield between treated and untreated Surpass 501 crops."
Both triazine-tolerant (TT) and imidazole-tolerant (IT) canola were used in the trial.
"ìThe overall trend here was that TT canola yielded better than IT canola, with the highest yielding TT canola yielding 1.8t/ha while the highest yielding IT canola yielded 1.5t/ha," Mr Quinlan said.