Wild radish may sound like a variety food in a rabbit’s diet,
but it’s a real pain in
Georgia wheat fields.

"We’re seeing wild radish as the No. 1 problem in small
grains this year,"
said Greg MacDonald, a weed specialist with the University of
Georgia Extension Service.

Wild radish can infest all of the small grains grown in
Georgia, the most important of
which, by far, is wheat.

The pesky weed reseeds itself year after year, and its seeds
are tough, so farmers must
be persistent to control it.

This low-growing member of the cabbage family steals water
and nutrients from young
grains. If the grain can’t get these vital things, MacDonald
said, it won’t mature
properly.

"It’s essential that the wheat get the water and
micronutrients it needs
now," he said, "to become strong enough to support a
mature grain kernel."

Wild radish can hurt at harvest, too, both by interfering
with equipment and by being
harvested with the grain, which can lower the crop’s quality
grade and, as a result, the
price the farmer gets for it.

MacDonald said farmers must act quickly to control wild
radish. They have only a brief
time to spray effective, legal herbicides.

"Most of the chemical herbicides that are effective on
wild radish can damage
wheat, especially, if they’re applied during an improper growth
stage of the grain,"
he said.

A wheat plant emerges with a main stem and then secondary
stems, or tillers, all of
which can produce seed heads which provide the plant’s yield of
grain.

Farmers can safely apply phenoxy herbicides, MacDonald said,
when wheat is between
three-tiller and full-tiller stages.

Applying before that can stunt the crop’s growth or reduce
tiller numbers. Applying
after the full-tiller stage can cause seed heads to be
malformed.

The good news is that wild radish plants are usually still
small at that stage of the
wheat plants’ growth, so herbicides can still easily kill
them.

Later, not only do growers risk damaging grain heads, but
larger radish plants are much
hardier.

"Once that radish plant bolts and sends up a flower
head, it’s extremely hard to
control," MacDonald said.

Many grain fields need nitrogen at this midseason growth
stage, too. So growers can mix
their liquid nitrogen and herbicide and do both jobs at once.

"The timing for both of those has to be just right,
though," MacDonald said.
"It’s a rather delicate timing factor."

Other herbicides, called sulfonylureas, effectively control
wild radish and can be
applied over a much longer time. But these products cost
slightly more than phenoxy types,
and they may be less effective on other weeds.

Growers must decide between these two types of herbicides
based on the growth stage of
their grain, the size and number of wild radish and other weed
plants and the relative
cost, MacDonald said.

Whichever they use, two factors are key: "Identify the
weed early," he said,
"and apply effective herbicides when grain plants will be
least damaged."