Ragweed
Common Ragweed (Ambrosia artemisiifolia) - Weed of the Year in 2011
Common ragweed is more common due to few effective herbicides in dry beans and sunflowers, increased presence around field perimeters, especially where perimeter management is not practiced, reliance upon POST herbicides only, and the increased selection of resistant biotypes to ALS inhibiting herbicides (Group 2), glyphosate (Group 9), and/or potentially PPO inhibiting herbicides (Group 14).
The majority of common ragweed populations in ND and MN contain some frequency of biotypes resistant to ALS-inhibiting herbicides. Currently, the greatest frequency of glyphosate-resistant common ragweed is found in Central Cass and Northern Traill Counties in ND and Western Becker, Eastern Clay, Southern Norman, Pennington, Red Lake, Stearns, and Todd counties in MN.
Biology of Common Ragweed:
Common ragweed is a summer annual producing up to 64,000 seeds per plant. Seeds require a dormant period before emergence and can stay dormant in the soil for many years. A combination of light and temperature trigger the germination process. Common ragweed emerges early in the season and continues to emerge until hot temperatures halt germination. Crop loss is maximized when common ragweed emerges at the same time as the crop and ragweed density increases. Crop loss is minimal if plants emerge three to four weeks after crop emergence. Common ragweed begins flowering as day length is reduced. A single common ragweed plant can produce greater than 1 billion pollen grains, making life miserable for hay-fever sufferers.
Management of Common Ragweed:
Common ragweed is most effectively controlled with a combination of PRE followed by POST herbicides. The frequency of herbicide resistant biotypes today forces the use of full rates of PRE herbicides. Apply POST herbicides to small (2 to 3”) plants to negate any impact from stem-boring insects. The more dense the ragweed population and the more extended the germination period, the more likely multiple POST applications will be required, even following a PRE herbicide. Research indicates that maximum glyphosate activity is usually achieved when common ragweed plants are less than 1 inch in height, including low-level glyphosate-resistant biotypes.
Chemical Control of Common Ragweed:
The herbicides listed below most effectively control common ragweed as long as enough rainfall is received to activate soil residual herbicides and POST herbicides are applied to small common ragweed:
Corn: See pages 18-23 for additional information. Soil-applied providing E control = Atrazine (0.5 to 0.75 lb ai/A)2 , SureStart2 , Tripleflex2
Soil-applied herbicides providing G-E control = Balance Pro / Flexx2 , Callisto2 , Lumax2 , Sharpen (3 oz/A), and Verdict (>12 oz/A).
POST herbicides providing E control = Atrazine (0.5 to 0.75 lb ai/A)2 , Banvel*, Buctril*, Callisto + atrazine2 , Halex GT2 (RR corn only), Hornet2 , Impact +atrazine2 , Laudis + atrazine2 , Lumax2 , Status / Distinct.
POST herbicides providing G-E control = Permit1,2, Roundup*2 (RR corn only).
Soybean: See pages 24-29 for additional information. Soil-applied providing E control = Authority First / Sonic1,2, Gangster1,2
Soil-applied herbicides providing G-E control = Boundary2, Authority MTZ2 , Sencor*
POST herbicides providing E control = Extreme1,2, FirstRate1,2, Flexstar2 (< 4” plants), Flexstar GT2 (RR soybean only)
POST herbicides providing G-E control = Cobra (< 2” plants), Ignite 280 (LL soybean only), Roundup*1 (RR soybean only)
Dry Bean: See pages 30-31 for additional information. Soil-applied providing E control = Permit1,2
Soil-applied providing G-E control = None
Soil-applied providing G-E control = None
POST-applied providing G-E control = Permit1,2, Reflex2 (< 3” plants)
Sugarbeet: See pages 42-43 for additional information. Soil-applied providing E control = None
Soil-applied providing G-E control = None
POST-applied providing E control = None
POST-applied providing G-E control = Roundup*2 (RR sugarbeet only), Stinger* (> 0.061 lb ai/A and < 2” plants?)
Wheat: Many herbicides used in wheat will control common ragweed. Most growth regulator herbicides (2,4-D, Banvel*, MCPA, Starane*, Stinger*) will give G-E control. Huskie, Supremacy, and many SU herbicides will also give E control.
*Or generic equivalent.
1 Will not effectively control resistant ragweed populations.
2 May carry over more than one cropping season, especially to sugarbeet. Follow labeled crop rotation restrictions. See pages 108-109.
