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JenREES 11/14/21

Grateful harvest has finished for most or will be hopefully wrapping up this week for the rest. Last week was seeing more fall herbicide applications being applied. If you have a 2021 Guide for Weed, Disease and Insect Management, page 93 provides fall burndown corn herbicide options and page 139 provides soybean ones (I also show these at https://jenreesources.com/). Most products contain 2,4-D and/or dicamba. Tank-mixing a residual herbicide with a burndown product will improve marestail control because the residual activity will control marestail emerging after herbicide application.

Regarding temperatures, Dr. Amit Jhala shared in a CropWatch article that the ideal temperature for applying most post-emergence herbicides is between 65°F and 85°F. Herbicides can be applied at 40°F to 60°F, but weeds may be killed slowly. When the temperature is below 40°F for an extended time after burndown, weed control will most likely be reduced, specifically for a systemic burndown herbicide such as glyphosate. Additionally, weed control may be reduced under cloudy conditions following an initial temperature drop below 40°F. With late-fall herbicide applications be sure to add labeled adjuvants to improve herbicide efficacy.

Actively growing weeds are key to achieving good control, regardless of herbicide used. Frosts of less than 25°F usually cause leaf damage to annual plants, making them poor targets for herbicide applications; however, winter annual weeds may tolerate a frost up to 20°F and continue growing when conditions improve, with little tissue damage. After weeds experience frost, active growth may not begin again for a few days. Growers should wait until new leaf tissue is produced, scout the field, and then consider applying herbicide. Generally, this would be when nighttime temperatures are 35°F or greater and daytime temperatures are at least 50°F for two consecutive days. Additionally, sunshine is needed for plants to recover.

Grazing fields with fall herbicide applications: Be sure to check labels for any grazing restrictions if livestock will graze cornstalks after in-season and fall herbicide applications. You can find these in the Forage, Feed, Grazing Restrictions area on pages 212-216 of the 2021 Guide. Some labels will say that residue should not be grazed or baled and fed to livestock. Sometimes there’s no guidance on the label. If you want to be on the safe side, a rule of thumb some chemical reps use is to use the pre-harvest interval for the amount of time to wait before grazing stalks. Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed as it is a legal document and the law.

As you plan for next year’s herbicide program, if you’re thinking about fall cover crops, the following NebGuide may be of benefit to you as it goes through the grazing restrictions of various herbicides.

Lawns and Leaves: The tree colors have been gorgeous the past few weeks and with colder temperatures, leaves are now dropping. If you have large, established trees like I do, they can pile up on a lawn rather quickly. Leaves should be removed by raking or mulching into the lawn by mowing in order to prevent damage to lawns over the winter from snow mold. If you choose to mulch leaves via the mower, raising the mower height two to three times will help break down the leaves and incorporate them. According to our turfgrass specialists, mulching grass clippings and leaves does not contribute to thatch development in the lawn.

Fallen leaves release phosphorus and nitrogen when they decompose, which can help with lawns and also with gardens if they’re added to garden sites as a soil amendment. When leaves are intentionally blown into streets, they can be a pollutant to surface water as they are washed away via storm drains.



Herbicide Grazing Restrictions

Forage Feed Grazing Restrictionscattle in corn stalks

Replant Options Rotation Restrictions-long

Grateful for a nice week for harvesting and for the good yields being reported!  It’s also good to see cattle being turned into cornstalks.  A reminder to read herbicide labels to understand if there’s any grazing restrictions from corn and soybean herbicides applied in-season.

It’s also important to look for any grazing restrictions on fall-applied herbicides to control marestail and other germinating weeds.  These restrictions can also be found in the Forage Feed Grazing Restrictions in the UNL Guide for Weed Management.  The forage, feed, and grazing restriction only applies to the crop for which the herbicide was applied.  When it comes to grazing cover crops planted into these residues, one must use the replant/rotation restriction guidelines found on the herbicide label and in the UNL Weed Guide: Replant Options Rotation Restrictions-long.  I apologize as these scanned blurry; hopefully you can zoom in ok to read what you need.

If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb is to use the pre-harvest interval for the amount of time to wait before grazing stalks.  Some labels will say that residue should not be grazed or baled and fed to livestock.  Sometimes studies were actually conducted to know there is a safety concern.  In other cases, the chemical company may not choose to conduct all the studies the Environmental Protection Agency (EPA) required for labeling due to high costs.  If that’s the case, the EPA requires the strongest restrictive language be placed on the label. Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed as it is a legal document and the law.

As you plan for next year’s herbicide program, if you’re thinking about fall cover crops, the following NebGuide may be of benefit to you as it goes through the grazing restrictions of various herbicides.

Forage, Feed, and Grazing Restrictions for Row Crop Herbicides

It’s nice seeing cattle being turned out into corn stalks! Cattle in Irrigated Cornstalks One point that I haven’t mentioned recently is that we all need to be checking the herbicide label for any grazing restrictions of crop residues.

So check the labels from in-season applied herbicides to row crops and fall-applied herbicides to crop residue for any potential grazing restrictions…and any restrictions on grazing cover crops planted into crop residues following application of those chemicals to a row crop.  If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb many chemical reps use is to use the pre-harvest interval for the amount of time to wait before grazing stalks.

Some labels will say that residue should not be grazed or baled and fed to livestock.  Sometimes studies were actually conducted to know there is a safety concern.  In other cases, the chemical company may not choose to conduct all the studies the Environmental Protection Agency (EPA) required for labeling due to high costs.  If that’s the case, the EPA requires the strongest restrictive language be placed on the label. 

Hail/rain/wind caused for soybean shatter and harvest loss. Volunteer beans have created green fields in the area. For those considering grazing, one needs to look at any herbicide grazing restrictions from herbicides applied in-season to soybeans as well. Dr. Bruce Anderson says, "Soybeans can cause bloat, but the incidence is low. The young green ones may be more risky. Founder would be possible problem with a sudden diet change. Too many unsprouted beans in the diet could cause excess fat; I think maximum is about 3 lbs beans per cow. I’d try to limit amount of grazing for a few days, maybe feeding a very palatable supplement like a ground forage/distillers mix and reduce the amount of this supplement each day for a week or so. And keep a dry, palatable hay always available free choice."

Hail/rain/wind caused for soybean shatter and harvest loss. Volunteer beans have created green fields in the area. For those considering grazing, one needs to look at any herbicide grazing restrictions from herbicides applied in-season to soybeans as well. Dr. Bruce Anderson says, “Soybeans can cause bloat, but the incidence is low. The young green ones may be more risky. Founder would be possible problem with a sudden diet change. Too many unsprouted beans in the diet could cause excess fat; I think maximum is about 3 lbs beans per cow. I’d try to limit amount of grazing for a few days, maybe feeding a very palatable supplement like a ground forage/distillers mix and reduce the amount of this supplement each day for a week or so. And keep a dry, palatable hay always available free choice.”  Additional information from the University of Missouri.   

Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed as it is a legal document and the law.  Your cattle may/may not be affected by grazing stalks or cover crops where a chemical with a grazing restriction is on the label, but there may be other concerns such as problems with the chemical affecting the calf or being retained in the cow’s milk.

For quick references, the 2015 UNL Guide for Weed Management shows Forage, Feed, Grazing Restrictions for Row Crop Herbicides on pages 174-177.  A new weed guide will be released January 2016.  These pages just provide a reference; it’s truly best to read and follow the label.

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