PPDL Picture of the Week
February 23, 2015
ID Weeds in the Field Margins
Travis Legleiter, Weed Science Program Specialist, Department of Botany and Plant Pathology,Purdue University
A great amount of effort has been put towards educating
Indiana farmers about the identification of Palmer amaranth over the last
couple of years by the Purdue weed science team. Identification of weed species is critical to
formulating a weed control program not only in corn and soybean, but any
situation in which weed control is the end goal. Knowing the correct identification of a weed
can help a person understand its biology and allow for alterations of the
growing conditions to inhibit the further competition of that weed. Often we emphasis on scouting for weeds
within an agronomic field, but often the weeds on the field margins are of just
as much importance.
The weeds growing on the field margins or margins of any
production area are often overlooked simply because they are not in direct
competition with the crop. These plants
are often just as important though, as they are often allowed to produce seed
and can quickly go from a species on the fringe of a field to the weed of
concern in the field. In the case of
Palmer amaranth, and many other agronomic weeds, these fringe plants contribute
a large amount of seed that is easily spread into the field negating any
efforts to reduce the seed bank within the field.
This weeks pictures come from southern Indiana along the
Ohio River bottoms where producers have been managing Palmer amaranth for a
couple of years. While driving around
this area last summer the majority of fields were clean of Palmer amaranth,
although along many of the field borders and in the road ditches there was many
places where palmer was flourishing.
Again these plants are not in direct competition with the cornfield
pictured behind them, but will produce seed the will likely be dispersed into
the field.
Secondarily, identifying weeds on the field margins can also
be beneficial in inhibiting new species from invading the field. Weeds often begin as plants on the fringe of
a field that go unnoticed and then quickly move into the field due to lack of
management. You will also notice in the
pictures several other weeds species including hophornbeam copperleaf (pictures
alone in pic 3). Hophornbeam copperleaf
is not a weed producers in Indiana often see, but it has slowly made its way
north from the Southern United States along with Palmer amaranth. The plants pictures will continue to grow and
produce seed that will likely be at least partially dispersed into the
cornfield behind it.
Weed management plans should have a goal of preventing weeds
from contributing further to the seed bank; this should include all plants in
the production field as well as the field margins. The next time you scout your fields, make
sure you take a look at the field edges as well for any suspicious new species.