NDSU Extension - Griggs County

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April 23

The Extension Connection Column by Jeff Stachler

Preparing for Early Weed Control in Soybean

Hello.  Hope you are having a great Friday! 

Ticks are back!  Ticks are external parasites that feed on blood.  The two most common ticks in North Dakota are the black legged or deer tick and dog tick.  The black legged/deer tick is the one to be most concerned about because it vectors Lyme disease.  Ticks mostly live on tall grasses and weeds, so be careful when walking in these areas and check yourself for ticks.  Applying 20 to 30 percent DEET to exposed skin and clothes will repel the ticks for several hours.  Remove all ticks as soon as possible, however you usually have at least 36 hours before the bacteria will travel from the tick into the host. 

Well the weather sure has changed!  I recorded 1” of snow this morning (Tuesday).  The soil temperatures are now down to 39 degrees Fahrenheit as of Tuesday morning after being in the fifties over the weekend.  It has been warm enough that some of the lettuce I planted on Good Friday is starting to emerge!

Planting is progressing nicely.  About 40% of the wheat has been planted in the county.  Some barley has been planted and one farmer was going to start planting soybean last Friday.

Now that soybeans are starting to be planted it is time to talk about early-season weed control.  If soybean will be planted no-till, it is important to control the weeds present prior to planting, especially if glyphosate-resistant kochia and marestail/horseweed are present in a field.  To control both of these emerged weeds apply glyphosate at 1.125 to 1.5 pounds acid equivalent per acre plus Verdict at 5 fluid ounces per acre plus a high surfactant oil concentrate plus ammonium sulfate.  Adding metribuzin DF at 0.33 pounds per acre will improve control.  Another option is to apply Paraquat at 3 pints per acre of a 3 pound per gallon product plus Verdict at 5 fluid ounces per acre plus metribuzin DF at 0.33 pounds per acre plus an oil adjuvant.  Adding 2,4-D ester to this mixture will improve control.  When using 2,4-D ester at 1 pint per acre of a 4 pound per gallon product soybeans can’t be planted until at least 7 days after application.  All of these combinations will also control emerged waterhemp, a pigweed species.

Unfortunately, none of these combinations will provide good residual control of kochia and waterhemp in soybean.  One option would be to increase the rate of Verdict to 7.5 fluid ounces per acre but this likely will not provide enough residual control and soybeans can’t be planted until at least 14 days after application.  One other option would be to include Authority Elite or BroadAxe XC with these herbicides mentioned above, but again planting of soybeans must be delayed at least 14 days after application of 5 fluid ounces per acre of Verdict and at least 30 days if coarse soils are present with less than 2 percent organic matter and using Verdict at 7.5 fluid ounces per acre.

If soils are prepared before planting with vertical tillage, it is a good idea to still apply burndown herbicides because not all weeds will be controlled.  If fields are field cultivated, burndown herbicides are not necessary.  If preparing the soil with a field cultivator, apply Authority Elite or BroadAxe XC after planting to control kochia and watehemp, the two most problematic weeds in soybean in Griggs County.  For these two herbicides to work most effectively rain must occur within 7 to 14 days after application.  Rainfall after this can still provide some control, but it will be limited.

If you have questions about weed control, feel free to contact North Dakota State University Extension office of Griggs County.  Have a great day!

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