Canola: the one in four law

Farmers who insist on sowing canola more than once every four years are putting the whole industry at risk.

The warning comes from Ted Wolfe, Professor of Agronomy at Charles Sturt University, citing a recent survey of research and industry leaders here and in Canada. They identified the development of herbicide-resistant weeds and the risk of disease as major threats to the security of the industry. "We're well on the way to inviting both disasters," he says.

"Any producer who puts too much reliance on the herbicide-tolerant canola varieties is simply inviting the development of herbicide-resistant weeds. Similarly anyone who flirts with canola-wheat-canola as a rotation is increasing the risk of the next blackleg epidemic. We don't have to look any further than the damage done to the livestock industries by the development of resistant parasites to get an idea of the financial consequences."

It's possible we'll "squander the benefits of herbicide-tolerant crops within 10 years," says Professor Wolfe. In the rush to more cost-effective management, some modern farmers are ignoring basic biological rules.

He said the first hint of herbicide-resistant weeds or disease build-up often comes from otherwise well-managed farms where the system is being pushed the hardest. "Farm managers need to take account of biological risk in planning any management strategy," he says.

Many good farm managers may have been encouraged to believe there is no limit to the possible technical advances in agriculture and that every problem has a magic bullet solution. Professor Wolfe believes that sort of naivete is particularly dangerous in the case of canola.

"It's quite possible that an outbreak of blackleg similar to that which struck the industry in the 1970s would take out many, if not all, of the current recommended varieties," he says. "We know that our blackleg-resistant varieties have robust resistance to the disease but we don't know if our current canola varieties have multi-gene resistance." (Important if the pathogen develops a new strain — Ed.)

Plant pathologists and agronomists in Western Australia are now recommending a strict disease prevention program. (See War in the West p5.)

Noting the rapid spread of the lupin disease Anthracnose in Western Australia, Professor Wolfe suggests the heavy dependence on lupins in the cropping rotation in that State has been a contributing factor. "In many ways it's a blueprint of what could happen in the canola industry," he says.