NDSU Extension - Griggs County

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May 7

Hello!  I hope all of you are doing well.  We had our first 80 degree day, but now we are back to below normal temperatures.

 

As of Monday, about 90 percent of the wheat and barley had been planted in the county.  About 35% of the corn and 5% of soybeans have been planted as of Monday.

 

Another weed of concern for the county is common ragweed.  Common ragweed has been confirmed resistant to ALS inhibiting (Group 2), PPO inhibiting (Group 14), and glyphosate in North Dakota, making it more difficult to control, especially in soybean and dry bean.

 

The scientific name for common ragweed is Ambrosia artemisiifolia.  Common ragweed belongs to the Aster or Asteraceae family.  Other common names for common ragweed include annual ragweed, wild tansy, hogweed, short ragweed, Roman wormwood, bitterweed, blackweed, carrot weed, hay fever weed, stammerwort, stickweed, tassel weed, and American wormwood.

 

Common ragweed should have or should be emerging now.  The cotyledons, the first structures visible after emergence which are remnants of the seed are round to spoon-shaped with black dots on the margin of the cotyledon.  The first true leaves emerge in pairs and have two or more lobes.  Subsequent leaves have additional and deeper thin lobes as compared to the first pair of leaves.  The first 4 to 8 nodes of leaves are paired or opposite, then the leaves have an alternate leaf arrangement.  The stem is hairy.  The plant is monoecious meaning male and female flowers are separated from each other on the same plant, like corn.  Therefore, the ends of all branches have male flowers only in spikes and the female flowers are found at the nodes surrounded by leafy structures called bracts.  The seeds are round with tapered edges and with spikes looking like a king’s crown.  Seeds are grey to light to dark brown and sometimes have stripes.

 

Common ragweed usually reaches a height of three to four feet, but can be as tall as six feet.  Common ragweed can produce up to 62,000 speeds per plant.  Common ragweed seeds can remain viable in the soil for greater than 39 years.


Common ragweed is native to North America and can be found in crop fields, gardens, railroads, lawns, pastures, roadsides, fence rows, ditch and stream banks, forest borders, farmsteads, weedy meadows, and waste areas.

 

The biggest problem with common ragweed is the copious amounts of pollen that the plant produces.  It is estimated that 1 million tons of ragweed pollen are produced each season in North America!  The pollen grains have spikes on them and irritate human noses causing allergic reactions and hay fever.

 

The goal to controlling common ragweed is to stop seed production since that is the only way it reproduces.  Frequent tillage of the soil can control common ragweed and frequent mowing can drastically reduce seed production.  Herbicides are the common method used in agriculture to control common ragweed.  Herbicides that will effectively control common ragweed include 2,4-D, Axial Star, bromoxynil, Carnivore, Curtail, dicamba, DiFlexx, DiFlexx Duo, Enlist Duo, glufosinate, Halex GT, Hornet, Huskie, Huskie Complete, Huskie FX, Lumax EZ, Orion, paraquat, PerfectMatch, Quelex, Raze, Resicore, Starane Ultra, Starane Flex, Starane NXT, Status, Stinger, Supremacy, Talinor, WideMatch, Wolverine Advanced, and Armezon, Capreno, Impact or Laudis plus atrazine.  Notice that most of these herbicides are used in wheat and corn, so control in soybean and dry bean is difficult. 

 

The best management strategy to controlling common ragweed is to apply a preemergence herbicide or herbicides followed by a postemergence herbicide or herbicides.

 

For home owners in non-crop areas, glyphosate (Roundup) can be applied at 1.125 pounds acid equivalent per acre, but the area will need to be scouted for surviving plants since glyphosate-resistant common ragweed is known to be present in North Dakota.

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