Features Agronomy Identity Preserved
A different mode of action

The registration of Syngenta's new corn herbicide, Callisto, has been long-awaited
in Canada, while US farmers have been able to use it since 2001. It is one of
few new products receiving approval for use in Canada and, importantly, it represents
a new class of chemistry and a different mode of action, which offers new weed
management opportunities for growers, including crop safety and flexibility
of timing.

A patch at the field edge where application was missed shows weed
pressure in Charlton's field.

Callisto contains the active ingredient mesotrione, which is in the triketone
family of chemicals, designated as Group 28 herbicide. Based on feedback from
more than 200 growers who have farm proven Callisto, Syngenta expects grower
interest in the one-pass tank-mix with Primextra II Magnum that can be applied
pre-emergence and early post-emergence. However, Callisto can also be applied
as a tank-mix with AAtrex + Dual II Magnum, or with Primextra II Magnum. It
may also be used post-emergence with AAtrex to the eight leaf stage of corn
or as a tank-mix with AAtrex (at one-quarter rate) + Ultim or Accent. It has
a high level of crop safety and can be used pre-emergence on seed corn and sweet
corn.

“The tank-mix with AAtrex is patented,” says Syngenta's corn and
soybean product manager, Kris Savage. “The addition of atrazine provides
a synergy that sharpens the performance of Callisto and speeds up its activity.”

The company had previously hoped to have registration for the 2004 growing
season, but Callisto has required the major, multi-disciplinary review required
for a new active ingredient entering the market and that takes time. Savage,
however, is pleased that the additional season has provided good field trial
experience. “Two hundred growers have now used the product in the two very
different seasons of 2003 and 2004 and they have proven that we can be confident
about Callisto's performance,” she says. “As well, PMRA's registration
system assures us that the product is safe.”

Sensitive vegetables

Initial work from Darren Robinson at Ridgetown College suggests there
will be plant-back issues in peas (and possibly snap beans) for at least
one year (possibly two) following Callisto use in corn. Other sensitive
vegetables include onions. Growers of these crops are advised to be cautious.

At Denfield, Ontario, Todd Charlton compared Callisto with his usual corn herbicide
program in 2004 under a research permit. “The field had a lot of ragweed,
lamb's quarters, velvet leaf and some nutsedge. There is not high pressure,
but we try to keep on top of weeds to keep it that way,” he says. He left
a check strip which only had Primextra PPI and the late emerging weeds were
prolific.

One of his usual strategies is to use pre-plant incorporated Primextra II Magnum,
then apply a post-emergence product as necessary. “We use Dual where we
know there's a nutsedge problem,” he adds. Another option is to use Dual
pre-emergence then Peak Plus. Having Callisto is an alternative to this strategy
which he expects to use on some of his 150 acres of corn, “so long as it
is price competitive,” he adds.