1. Managing Tough Weeds with Enlist and Extend Weed Control Systems
Tom Peters
Extension Sugarbeet Agronomist
North Dakota State University and the University of Minnesota

2. Waterhemp in soybean, 2014 Renville County, MN

3. Waterhemp, an assessment by county
Waterhemp in 2015

4. Waterhemp in 2015 Walsh County Polk County, Euclid, MN
SR 200, Norman, County
Traill County

5. Common Ragweed
Kochia
More problematic with increase in soybean and dry bean acres
Germinates in the spring but returns to dormancy when temperatures get hot in June and July
Germination at our near the soil surface
Control when three inches or less
Resistant biotypes to multiple classes of herbicides
ALS (SOA 2)
PPO inhibitor (SOA 14)
Glyphosate (9)
Extremely competitive weed; a few plants can cause yield reduction
Many document examples of herbicide resistance
2,4-D and MCPA (SOA 4)
ALS (SOA 2)
Glyphosate (SOA 9)
Control in the crop sequence, small grains and corn
In sugarbeet, control POST when kochia is small
Kochia seeds loose viability after one or two years

6. Enlist or Xtend soybeans will be arriving soon
How will the system perform on tough-to-control/ resistant weeds in YOUR FIELDS?
2,4-D
dicamba
Kochia
N/P E
Common ragweed
Waterhemp F
F/G
Marestail
Palmer amaranth
Scale:
E = Excellent = 90 to 99%
G = Good = 80 to 90%
F = Fair = 65 to 80%
P = Poor = 40 to 65%
N = No Control
A product of a conversation with Dr. Richard Zollinger, NDSU Weed Science

7. 2,4-D Herbicide
Synthetic auxin herbicide in the phenoxy chemical family
First used in the U.S. in the 1940s and marked the beginning of the selective chemical weed control era
One of the most widely used herbicides worldwide
Controls annual and perennial broadleaf weeds in grass crops
Would offer a different mode of action for control of tough-to-control broadleaf weeds in soybean
Slide credit: Dr. Jim Griffin, Louisiana State University

8. Dicamba Herbicide
Synthetic auxin herbicide in the benzoic acid chemical family
Discovered in 1958 and first marketed in 1964 as Banvel DMA salt
Clarity DGA salt marketed in 1992
Sixth most widely used herbicide in the U.S., with more than 25 million acres of farmland treated annually
Controls annual and perennial broadleaf weeds in grass crops
Would offer a different mode of action for control of tough-to-control broadleaf weeds in soybean
Slide credit: Dr. Jim Griffin, Louisiana State University

9. Enlist Weed Control System 2,4-D Tolerant Crops (Dow AgroSciences)
Crop tolerance in transgenic plants achieved through insertion of the aad-12 gene that encodes for a bacterial aryloxyalkanoate dioxygenase enzyme (metabolism/deactivation gene)
Production of enzyme leads to breakdown of 2,4-D to the non-herbicidal dichlorophenol.
In corn, the enzyme will also lead to the breakdown of the ayloxyphenoxy propionate (fop) herbicides: fluazifop (Fusilade), quizalofop (Assure) H
2,4-D acid
dichlorophenol
____________________________________________________________________
phenoxy
Slide credit: Dr. Jim Griffin, Louisiana State University
Fusilade (fluazifop)

10. Roundup Ready Xtend Crop System Dicamba Tolerant Crops (Monsanto)
Discovery at University of Nebraska of soil bacterium (Pseudomonas maltophilia) that metabolizes dicamba to a non-herbicidal/inactive form (Science 2007)
Crop tolerance in transgenic plants achieved through insertion of a gene that encodes for a bacterial DMO (dicamba monooxygenase) enzyme (metabolism/deactivation gene)
Production of DMO leads to breakdown of dicamba to the non-herbicidal 3,6-dichlorosalicylic acid
Slide credit: Dr. Jim Griffin,
Weed Scientist, LSU H
3,6-dichloro-o-anisic acid (dicamba acid)
3,6-dichlorosalicylic acid (non-herbicidal)

11. Available Sites of Action By Crop
Site of Action (SOA number)
Corn PRE
Corn POST
Soybean PRE
Soybean POST 2 4 3
[9] 5
[10]
15 (ePOST) 14 27
Reliance on a single SOA across crops/years increases the likelihood of resistance
Generational differences in weeds from season to season
[ ] = GMO
Slide developed in collaboration with Dr. Mike Christoffers

12. Concerns/Issues Dicamba and 2,4-D Technologies
Labels will be very specific and restrictive
Crop sensitivity
2,4-D on sugarbeet and dicamba on soybeans
Like Brylcreem, “a little dab’ll do ya!”
These herbicides “will tell on you!”
Off-target movement
Volatility not likely to be major contributor; companies have developed “low volatile” formulations
Physical drift – affected by droplet size, spray pressure, nozzle type, boom height, wind speed, etc.
Spray tank contamination/sprayer clean-out
Slide credit: Dr. Jim Griffin,Weed Scientist, LSU

13. Summary
Enlist and Extend require EPA approval and China grain import approval before they will be available for sale
Dow AgroSciences and Monsanto are preparing for launch
Both technologies will require use of spray nozzles that produce a large droplet spectrum
Both technologies have a much more restrictive label than past new products
Prevention of particle drift to susceptible non target plants will be an important management strategy

14. Thank you for your Attention and your Support
Tom Peters
Extension Sugarbeet Agronomist and Weed Control Specialist
Thomas
(office)
(mobile)