Pest Profile: Fall Panicum and Foxtail Grasses

Persistent and resistant weeds like fall panicum and yellow and green foxtail can damage yields and raise costs.

A Tale of Three Foxtails

The three most common foxtail weeds in the U.S., common in corn, soybeans and wheat alike, are giant, green and yellow foxtail. Penn State Extension explains the differences between the three types: green and yellow foxtails are named for the color of the fuzzy bristles (awns) on their seeds. Giant foxtail (Setaria faberii) has a large drooping seed head that grows up to 8 inches (20 cm) long.

Once a weed like giant foxtail establishes its foothold in a field, it can take five years to reduce the seed bank by just 50 percent, according to Michigan State University Weed Science. The university also reported that even a very conservative giant foxtail presence – just three per square foot – reduced corn yields by as much as 14 percent. Chemical control of giant foxtail in broadleaf crops, such as soybeans, is fairly easy with the available soybean trait and chemistry technologies. Any type of foxtail is more challenging to control in corn or wheat, as both plants are grasses. In wheat, green foxtail infestations of 97 plants per square meter resulted in a yield loss of 8-44 percent.

Mistaken Identity

A fourth weed is commonly mistaken for green foxtail – fall panicum. According to Penn State Extension, “Both grasses have smooth or sparsely hairy leaf blades, as well as split, partially overlapping leaf sheaths. The leaf sheath margins of green foxtail, however, are densely lined with upward pointing hairs, while those of fall panicum are smooth.” While the differences become more evident in fully-grown plants, they are virtually indistinguishable when they are seedlings.

fall panicum
Fall Panicum immature (left) and mature (right)
Green Foxtail
Green Foxtail immature (left) and mature (right)

Fortunately, there is a way to quickly and effectively manage these weeds and protect yields. The University of Missouri Extension recommends using a pre-emergence herbicide as part of a two-pass system to control foxtails and fall panicum.

Solutions for Corn & Soybean Growers

Corn growers depend on pre-emergence herbicides to control early season problem weeds. Corvus® pre-emergence herbicide from Crop Science is the only corn herbicide to offer burndown, residual and reactivation. Residual activity prevents new weeds, while reactivation controls late weeds

The multiple modes of action in Corvus deliver consistent, broad-spectrum control of grasses and broadleaf weeds, including weeds resistant to glyphosate-, ALS-, PPO- and triazine-based herbicides.

A wide application window allows for application from pre-plant to early postemergence at V2, making it an effective, long-lasting first pass herbicide in a two-pass system. Depending on the weed spectrum in your field, such as fields without heavy Palmer amaranth and waterhemp pressure, Corvus may still be a great one-pass option.

A recommended two-pass program starts with a pre-emergence application of Corvus herbicide. The second pass should include a postemergence product such as Laudis® herbicide. If using Laudis following an application of Corvus, add another herbicide with a different mode of action, such as DiFlexx® herbicide or atrazine, to ensure you are using multiple modes of action in your weed control.

Capreno® herbicide is another postemergence herbicide option for corn. It has the longest-lasting residual of any post product on the market.

Liberty® is the preeminent weed management system with a unique chemistry and novel mode of action to offer superior control of a broad spectrum of resistant and tough to control weeds in LibertyLink® soybeans, corn, cotton, and canola.  In fact, it is the ONLY non-selective post-emergence herbicide that still effectively handles grasses and broadleaf weeds including glyphosate resistant Palmer amaranth, giant ragweed, marestail, waterhemp, foxtail, fall panicum and kochia.

Answers for Wheat Growers

Chemical weed management is also key for controlling foxtails in wheat. A number of herbicides provide effective control of many key weeds, and Crop Science offers three herbicides for controlling green and yellow foxtail. There also are a number of modes of action to choose from to help you manage herbicide-resistant weeds.

For example, Huskie® Complete herbicide is available to wheat growers in Colorado, North Dakota, South Dakota, Minnesota, Montana, Wisconsin and Wyoming. This all-in-one wheat herbicide carries a chemistry previously not available for wheat, controlling green and yellow foxtail along with 50 grass and broadleaf weeds. Huskie® herbicide is available to wheat growers in 40 states and includes a unique mode of action in cereals, which is responsible for controlling broadleaf weeds, such as kochia, Russian thistle, prickly lettuce and wild buckwheat—including ALS- and glyphosate-resistant biotypes.

Because Crop Science continuously provides growers with new solutions to weed management problems, the company is excited to announce the release of two new wheat herbicides. The first is Varro™, which controls grass weeds and is available in Colorado, North Dakota, South Dakota, Minnesota, Montana and Wyoming. Green and yellow foxtail as well as barnyardgrass are controlled by Varro. Just as important, Varro allows a wide range of choices when it comes to broadleaf tankmix partners—while enhancing the performance of those partners.

Wheat growers also have the option of a second new herbicide, Wolverine® Advanced. Wolverine Advanced controls 69 grass and broadleaf weeds in wheat, thanks to three modes of action in a single product. This  unique combination of modes of action control green and yellow foxtail and barnyardgrass in addition to broadleaf weeds, such as kochia, Russian thistle, prickly lettuce and wild buckwheat – including ALS-and glyphosate-resistant biotypes.Wolverine Advanced is available in Idaho, Minnesota, Montana, North Dakota, South Dakota, Washington, Wisconsin and Wyoming.

Talk to your Crop Science representative about how to manage difficult weeds in an economically feasible manner.

Works Cited

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