Late flushes of weeds are a challenge, due to high
herbicide costs.
Dryland corn production in the Central Great Plains is always dicey. Most growers shoot for 50 bushel corn at a minimum and don't budget more than $15.00 per acre for herbicides. The majority of farmers with multi-crop rotations in dryland agriculture practice no-till or minimum-till farming to conserve the moisture necessary to sustain consecutive crops. Less tillage typically puts more emphasis on herbicidal weed control.
Growers often apply glyphosate (Round Up, Touchdown, and others) preplant or preemergent to the corn and control early emerging weeds. Later occurring flushes of sandbur, crabgrass, witchgrass, kochia, pigweed species and Russian thistle are often quite a problem in dryland corn. Herbicides exist that will effectively control these species of weeds, but often they are not cost effective. The most commonly used herbicide in dryland corn is atrazine, which is inexpensive and provides residual activity. Unfortunately, the above mentioned grass species are tolerant to atrazine, and at least 50% of Colorado kochia and pigweed populations have developed resistance to atrazine.
The photo shows control of a heavy sandbur infestation in dryland corn following a roundup application.
The herbicide treatments listed in Table 12 were applied June 21 on dryland
corn plots located at the Akron Central Great Plains Research Station.
The list does not include all herbicides available for dryland corn production,
nor is it intended to endorse any specific products. The treatments were
selected because of cost efficiency and/or recent registration being of
interest to the agricultural community. Hopefully, when touring these
plots in August, discussion will take place comparing these products to
similar ones in terms of relative effectiveness.
Roundup Ready corn is a good choice for combating weeds in dryland corn. Glyphosate products such as Roundup Ultra Max and Touchdown IQ can only be applied over Roundup Ready corn. A tech fee of $17.00/bag of corn is assessed, and, when spread over approximately 5 acres, comes to $3.00 - $4.00 per acre. Glyphosate products are becoming less expensive and provide excellent broad spectrum weed control with no rotational restrictions. The advantages of glyphosate for weed control are: no rotational restrictions from residual soil activity, broad spectrum weed control, and relatively low cost. The above treatments include Dual II Magnum for residual control of subsequent weed flushes.
Distinct, a premix of dicamba (Banvel, Clarity) and diflufenzopyr provides excellent broadleaf weed control and suppression, though not control, of grass species. There is a four month plantback restriction to all crops, following application of Distinct.
The tank mix of 2,4-D + atrazine is the least expensive treatment and, depending on the weed spectrum present, may provide adequate weed control.
Option is a new sulfonylurea herbicide from Bayer (formerly Aventis). Option provides good to excellent grass control and fair to good broadleaf weed control on sulfonylurea susceptible weed species. Methylated seed oil must be used with Option (not NIS or COC) for effectiveness. Option has a 90 day plantback interval to any crop.
Aim is a contact herbicide from FMC that provides good to excellent broadleaf weed control. Weed size and surfactant quality are critical for maximum effectiveness. Aim has no soil residual activity nor plantback restrictions to dryland crops.
Callisto is a new herbicide from Syngenta that controls
most broadleaf weeds and has good activity on wild proso millet and crabgrass.
Callisto has best activity when applied with atrazine. This product has
plantback restrictions. Refer to the label for details.
Marksman is a pre-mix of dicamba and atrazine that provides excellent
control of most broadleaf weeds but misses grass species that are tolerant
to atrazine.
Basis Gold is a pre-mix of nicosulfuron, rimsulfuron,
and atrazine. This product provides excellent grass control and good to
excellent broadleaf weed control. Plantback restrictions exist.
Russian Thistle
