GENET archive


2-Plants: Canadian study sceptical on HR-canola cost advantages

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TITLE:  Benefits of herbicide-tolerant canola systems vary, study
SOURCE: Lethbridge Research Centre Report, Canada
DATE:   January 13, 2000

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Benefits of herbicide-tolerant canola systems vary, study shows

Lethbridge, Alberta -- Western farmers have rapidly adopted
herbicide-tolerant canola (HTC) systems in recent years, but the
benefits of choosing those systems over conventional canola
production are not as black and white as farmers may expect. A
recent two-year study at the Agriculture and Agri-Food Canada
sites in Lethbridge and Lacombe, Alberta, in Scott, Saskatchewan,
and in Brandon and Morden Manitoba, shows that while HTC systems
offer a large weed control advantage in most areas, that doesn't
necessarily translate into a huge yield advantage over
conventional canola systems.

The study compared three widely-grown HTC systems with a
conventional canola system using post-emergence herbicides.
Overall weed control ranged from 93 percent weed control in
glyphosate (Roundup)-tolerant canola, to 84 percent for
imazethapyr/imazamox (Odyssey)-tolerant canola, 73 percent weed
control for glufosinate (Liberty)-tolerant canola, and 37 percent
for the conventional sethoxydim/ethametsulfuron (Poast/Muster)
canola treatment. Overall yields ranged from 49 bushels per acre
for glyphosate-tolerant canola, to 42 bushels for imazethapyr
imazamox-tolerant canola, to 40 bushels for glufosinate-tolerant
canola, and 38 bushels for the conventional canola treatment.

"The herbicide-tolerant canola systems were not as much of a
yield advantage as producers may have thought," says Blackshaw. A
big factor was the presence or absence of weeds that are hard to
control under the conventional system. "If you had a big problem
with stork's-bill or cleavers, then the herbicide-tolerant system
was a huge advantage, because we really couldn't control those
weeds at all in the conventional system." he says. "But in most
cases, we found that if you control your most competitive weeds,
such as wild mustard or wild oats, the yield with the
conventional system is not that much lower."

In 1999, approximately 80 percent of the 5.6 million hectares of
canola in Western Canada were seeded to HTC. In general, HTCs
simplify herbicide application for farmers, offering a broader
spectrum of weed control in a form that is easier to apply
effectively. In the study, the most dramatic advantages of HTCs
were at the Lacombe and Lethbridge, Alta. sites, where HTCs out
yielded the conventional system by 13 to 39 percent; stork's bill
was a large factor at both sites, as was cleavers at the Lacombe

"Stork's-bill is becoming more widespread across the prairies,
but it's a major problem in Alberta, particularly in east-central
Alberta," says Blackshaw. "Cleavers are also a big problem in
central Alberta, and they have become more prominent in
Manitoba." At the other end of the spectrum was the Scott, Sask.
site, which showed comparable yields in both HTC and conventional
systems. It's also important to note that post-emergence
application used in the study may be less effective than other
herbicide applications producers use with conventional systems,
so the performance results of this system are likely
conservative, says Blackshaw.

"In some areas, producers using conventional systems are actually
attaining similar yields and sometimes realizing more net income
because of lower seed and herbicide costs than with HTC systems,"
he says. "They can do quite well, particularly if they're
controlling weeds on their farm in other ways, through rotations
and other management." The wide disparity between the weed
control results compared to the yield results also serves as a
caution to producers who may be setting their control targets too
high, says Blackshaw. "Better weed control doesn't always
translate into a higher yield."

However, a clear advantage of the introduction of HTCs is that
farmers now have more weed control options, he says. With proper
management, that can help the industry develop improved weed
control strategies and more sustainable systems. That includes
such things as herbicide rotations, which will help prevent the
build-up of herbicide-resistant weed species. 


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