Top Crop Manager

Features Agronomy Harvesting
Timeliness critical factor in application of fungicides

Timing more important than method: ground or air.

November 20, 2007  By Top Crop Manager

Summer 2005 was a wet one. Farmers in large parts of Manitoba, Saskatchewan
and southern Alberta fought an uphill battle to get their waterlogged fields
seeded and sprayed. To make matters worse, the hot humid conditions were perfect
for the development of crop diseases in many areas. Often in conditions like
these, only a timely fungicide application will save the crop. But how can you
be timely when fields are too waterlogged to use a ground sprayer?

The answer, according to a new two year study by BASF and the Manitoba Aerial
Applicators Association, is simple. Use an airplane. The joint study shows it
is just as effective to spray fungicides (Headline and Lance were used in this
study) by air and by ground.

The study, which was conducted by AXYS Agronomics of Winnipeg, examined whether
the application method mattered when applying fungicides. The study compared
air and ground application of Headline to control leaf diseases in wheat. It
also compared application methods for Lance to control white mould in beans
and sclerotinia in canola. So, does application method matter? The results were
conclusive: No!


The study found no measurable difference in yield between plots sprayed by
plane and those sprayed by a ground sprayer. There were, however, big differences
between treated fields and untreated checks. Canola fields sprayed with Lance
yielded 23 percent more than the untreated checks.

"We found the same level of disease control and the same yield increase
whether Headline or Lance were applied by ground or by air across all locations,"
Nathan Froese, a field biologist with BASF, says.

"If we've learned anything with this study it was that producers should
treat the crop for disease regardless of the application method," Darren
Keam, project manager with AXYS Agronomics says. "We concluded that the
treatments did reduce disease infection compared to an untreated check, but
there was no significant difference between the air treatment and the ground

This study reinforces the results of a separate study headed by Tom Wolf at
Agriculture and Agri-Food Canada (AAFC) and Sabine Banniza at the University
of Saskatchewan that was conducted in Saskatoon during 2003/2004. Their study
comparing aerial and ground application of fungicides on chickpeas showed that
proper timing was far more important than application method.

"After two seasons' worth of work, the bottom line conclusion of our study
was that fungicides are highly effective at controlling disease and that the
application method had no effect," Wolf says. "If it's too wet to
use a ground sprayer, you can use a 'plane or if the airplane can't come for
a week, you can use a ground sprayer. It's more important to do it at the time
that the crop needs it."

In Wolf's study too, the differences between treated and untreated fields were
remarkable. Between July and harvest, disease increased from three percent to
99 percent in untreated chickpea plots. And, treated fields averaged 33 bushels
per acre in 2003 while untreated fields averaged only 13 bushels.

Since coverage is critical for an effective fungicide application and ground
sprayers can apply a high water volume, the results, at first glance, may seem
counter-intuitive. Keam though was not surprised. "It's been shown over
many studies that fungicides are effective regardless of the treatment method,"
Keam says. "Air and ground application results are similar in many cases
that I have read up on."

Matt Bestland, past president of the Manitoba Aerial Applicators' Association,
current president of the Canadian Aerial Applicators' Association and owner
of Bestland Agro in Brunkild, Manitoba, feels there are three reasons supporting
the consistent results of both studies. "One reason is compaction and yield
loss due to wheel tracks. Another would be potential spread of disease by the
ground machine. For example, with late blight in potatoes, the last thing the
grower wants to do is spread it by driving a contaminated unit up and down the
field. We also think that the downdraft from an airplane propels the fungicide
and droplets into the canopy with a greater force."

"It's important to spray at the right time and that is where I think the
aircraft business might have real strength," Wolf says. "A 'plane
has the ability to treat the field quickly, regardless of soil moisture. That
seems to be very important, particularly with diseases like ascochyta in chickpeas,
where we have such a rapid spread of the disease. If you aren't out there at
the right time, it won't work optimally no matter how you apply it." -30-



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