The value of a preemergence herbicide
Controlling weeds on the farm may be more of a challenge these days. Perhaps there is more giant ragweed or waterhemp in the fields, or perhaps controlling some of these populations is more difficult and herbicide resistance is suspected.
Including a PRE herbicide in the weed management program provides more than weed control (Figure 1). Choosing the right PRE for the weeds on the farm builds a foundation that helps:
- control primary weed species
- decrease the density of weeds
- provide a uniform weed size for postemergence (POST) herbicide applications
- increase or widen the window of time for the POST herbicide application
- increase the number of herbicide Groups used to control weeds
- complement successful row cultivation
Corn herbicide trials - Supporting data
- 2016 Evaluation of the weed spectrum and duration of control achieved with preemergence applications of Acuron and Acuron Flexi in field corn at Rochester, MN.
- Comparisons of PRE/POST weed control programs in field corn at Rochester, MN in 2016
- Comparisons of herbicide systems for weed control in field corn at Rochester, MN in 2016
Preemergence herbicides in soybean
Figure 2. Comparison of weed control with PRE applied herbicide BroadAxe XC to PRE applied Surveil on June 10, 2016 in soybean. Click to enlarge.
Soybean herbicide trials - Supporting data
- University of Minnesota 2016 statewide soybean weed management at Rochester, MN.
- Giant ragweed control in soybean - Demonstration of the advantages of a full spectrum residual herbicide program in soybean at Rochester, Minnesota in 2016.
Additional challenges with herbicide resistance: New technologies
Managing ALS (Group-2) and glyphosate (Group-9) resistant giant ragweed and waterhemp and in some fields, PPO (Group-14) resistant waterhemp in soybean fields poses many challenges. Starting with a good foundation and using technologies other than glyphosate, such as LibertyLink or dicamba tolerant soybeans provides additional postemergence herbicide options. However, to be successful with any of these technologies, it is important to start with a good preemergence herbicide foundation. These PRE herbicides foundations should and can be used in conventional, glyphosate, glufosinate or dicamba soybean systems.
It is crucial be good stewards of these technologies. Weed populations are dynamic and problems will continue to escalate unless strategies are developed to address these changes. In the trials at Rochester, many herbicide systems in corn and soybeans are evaluated, including a variety of herbicide-tolerant technologies. Trials in 2016 included soybeans tolerant to Group 10 (glufosinate), Group 4 (dicamba and 2,4-D), and Group 27 (HPPD) herbicides. These technologies bring a different herbicide group to soybeans, but they do not bring a NEW herbicide group to the world of weed control. Since these technologies are currently used in corn and other crops, many weed populations are exposed to the same herbicide group in consecutive years. To confound this, dicamba and 2,4-D herbicides have been used since the 1960s and no new herbicide SOA or Group has been discovered since the 1980s. Industry experts suggest it will take a minimum of 15 years to develop and discover a new SOA. Therefore, it is imperative that these tools and technologies are preserved by being good stewards and implementing non-chemical options to our weed control plans.
Figures 3 and 4 demonstrate the value of including a PRE herbicide in a glufosinate and dicamba system.
Read the complete reports on glufosinate, dicamba, 2,4-D and HPPD
- Managing glyphosate (Group-9) and ALS (Group-2) resistant common waterhemp with different systems and herbicide rates in LibertyLink soybean in SE Minnesota in 2016.
- 2016 Demonstration of the herbicide components in dicamba soybean, PRE plus POST and POST only applied at 3 and 6 inch weed at Rochester, MN.
- 2016 Evaluation of Enlist Duo for control of broadleaf weeds in soybeans at Rochester, MN.
- Evaluation of difficult to control broadleaf weeds with an HPPD herbicide based program in soybean in SE Minnesota in 2016.
Mechanical cultivation in soybean
Figure 5. Comparison of Boundary (5,15) applied PRE followed by either POST Liberty (10) at 29 fl oz/a on June 8 or a mechanical cultivation on June 21 for weed control and yield in soybean, 2016. Click to enlarge.
When developing weed management strategies and plans, it is important to add non-chemical control options to the weed control plan. These could include practices such as delayed planting, additional tillage, row cultivation, hand rogueing and cover crops. To demonstrate this, mechanical cultivation was evaluated in 2016. The trial compared a preemergence application of Boundary at 1.95 pt/a followed by either Liberty at 29 fl oz/a or by a mechanical cultivation. Final waterhemp control was significantly better with the Boundary/Cultivation treatment (98%) compared to the Boundary/Liberty program at 89% (Figure 5). The soybean canopy also closed sooner where cultivation occurred, so waterhemp that emerged under the canopy in July after cultivation did not survive. In addition, soybean yield of each treatment was similar and equal to the top yielding treatment in this trial. The Boundary/Cultivation treatment was also evaluated in 2015 with similar results for weed control, canopy closure and final yield.
For more details
- Managing glyphosate (Group-9) and ALS (Group-2) resistant common waterhemp with different systems and herbicide rates in LibertyLink Soybean in SE Minnesota in 2016.
- Managing glyphosate resistant common waterhemp with different systems and herbicide rates in LibertyLink soybean in SE Minnesota in 2015.
- 2016 Southern Minnesota crops research reports
Note the use of trade names is for clarity and educational purposes only and does not imply endorsement of a particular brand or product over another. Likewise, exclusion does not imply non-approval.