Late planting challenges weed control

Ohio crop growers faced numerous challenges planting corn and soybeans this
spring, and with the crop progressing through mid-July, they now face an
interesting weed control scenario, as well.

"The late planting presents challenges and makes weed control easier at the
same time," said Mark Loux, Ohio State Extension weed specialist. The
unusual planting season resulted in an abnormal timeline for producers' weed
control systems.

Because farmers couldn't get into fields as early as they would have liked
to this spring, Loux said farmers saw significant weed pressure throughout
June in both no-till and conventional tillage fields. In addition, some
producers were not aggressive enough with their application of a burndown
herbicide in no-till, and some weeds simply survived tillage this year.
Perhaps the biggest challenge to producers' weed control strategies boiled
down to simple logistics.

"When we're planting that late, everyone gets jammed up and some missed
applications," Loux said. "So, we have some fields that are really clean and
some that are really messy."

In his travels around the state Loux said he was concerned that some
producers had not yet sprayed a post-emergence herbicide. There is no point
in waiting, he said, because establishing control of weeds as early as
possible is critical in late planting situations.

Aside from the obvious challenges, a potentially shortened growing season
does yield some positive impact on weed control.

"The good news in a late planting situation is you don't have as many weeks
of weeds, and the crop grows faster," Loux said. "If you start weed-free and
make that work, you can spray your post-emerge a little earlier and it makes
control a little easier if you get the right start."

He continues to see glyphosate-resistant marestail as the key weed problem
in the state, and 2011 may prove to be an enlightening year for some farmers
because of the late planting.

While traditionally found in the southwestern portions of Ohio, Loux said
resistant populations of marestail are now found throughout the state.
"We have a lot of marestail this season," he said. "We can't control it
post-emergence very well. We have some problems in beans because farmers
didn't pick the right combination of burndown herbicides, or they didn't
want to spend enough money."

He also noted that in some cases, control efforts proved challenging because
burndown application timing was much later than usual this season, and
accordingly some products didn't work as well as in a typical year.

Since control efforts were hampered in some areas, Loux is hopeful affected
producers will better understand how significantly their fields are infested
with resistant weed populations and plan accordingly for next year.

"Because we have up to two types of resistance in some marestail
populations, the biggest thing is to realize you have a problem," he said.

"More of it is going to go to seed this year than last year. When you plan
for next year, consider a fall application of herbicide, and be aggressive
enough to control it next year."

The basic control recommendation in no-till soybeans, where Loux sees the
most weed control issues, is to use a comprehensive spring burndown
herbicide protocol while using the correct rate of a residual control
product at the same time. Beyond that, farmers can modify a post-emergence
application of glyphosate as needed.

He said some plans do include a fall application for marestail or other
problem weeds, as well.

"For historically resistant fields, farmers can consider some Liberty Link
soybeans to break up the use of glyphosate and get those issues under
control," Loux advised. "Some farmers aren't willing to do that, though,
because the variety selection there isn't as diverse."


Fuente: DCN

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