TOO MUCH OF A GOOD THING MULTIPLE VARIETIES MANAGE RISK

TOO MUCH OF A GOOD THING

MULTIPLE VARIETIES MANAGE RISK

SRA District Manager Burdekin Terry Granshaw has been around the industry long enough to have seen the financial impacts of having a large volume of a single variety of cane when something goes wrong.

Like Rob Milla, he is a strong advocate of managing risk through planting multiple varieties.

“Every time we’ve seen 60 per cent of a district growing a single variety, we always seem to have some sort of issue that follows it,” Terry explained.

“We had a massive amount of KQ228A as standover in 2010 when we had a La Niña event. And it didn’t stand up well – it just didn’t perform and had very poor CCS.

“And of course, Q124 down in Mackay. It was at 85 per cent and then orange rust came in and the result was very significant yield reductions.”

SRA Pathologist Rob Magarey understands farmers’ desire to grow the highest producing variety possible but said most disease epidemics in the Australian industry have occurred when a single variety was dominant in a mill area.

“What we've noticed over time is that when a single variety dominates the variety scene, it gives great opportunity for any organism that can attack the cane to multiply, grow and quickly escalate,” Rob said. “The longer we see a variety grown in a large part of the mill area, the greater the chance of organisms building up in that cane to colonise it.

“We’re growing monoculture for a period of five to six years with the same crop and the worst case is to a have a single variety. Not only a single crop, but a single variety.”

Rob said the rapid onset of orange rust in the Mackay district resulted in the most widespread, severe disease occurrence and largest single-year financial losses of any of the epidemics.

He said there is a strong correlation between the percentage of an area planted to one variety and the occurrence of a major disease epidemic.

“The safest option is to grow a range of varieties so that disease risk is minimised, with at least one likely to have sufficient resistance to withstand a disease incursion,” Rob said.