The Efficacy of Herbicide Modes of ction in Roundup Ready and LibertyLink Systems In agriculture, we are always looking for the next new tool or management practice that will allow us to become even more successful. When it comes to weed control, new opportunities are very limited even though new trait technologies are either on the market or pending approval. In the past few years, there has been a limited release of new herbicide active ingredients. It s been almost two decades since a new mode of action has been released. With fewer herbicide modes of action and active ingredients available, weed control has become even more challenging than in past years. One approach to managing hard-to-control weeds is to combine herbicide active ingredients that are already on the market to create a program with multiple modes of action. This approach can help answer questions like Can I still be successful in a Roundup Ready system? and How should I manage the LibertyLink system to prevent resistance? In 2016, eck s Practical Farm Research (PFR) evaluated the DM s Five X 5 system in both a Roundup Ready and LibertyLink scenario at our Southern Illinois PFR site. The Five X 5 system compares five modes of action to two modes of action, in an attempt to showcase the strengths and weaknesses of different herbicide active ingredients. This study also included other forms of the same active ingredient from different companies. The Five X 5 system strategically uses active ingredients that have been on the market for many years. Some of these products have both pre-emergence (PRE) and post-emergence (POST) activity on weed control, so application timing is crucial. The Five X 5 system takes advantage of products that contain PRE and POST activity as well as products that just have residual or POST activity. Figure 1. Herbicide Groups, ctive Ingredients and Manufacturers Herbicide Group Herbicide Herbicide ctive Ingredients Manufacturer 2 (LS) Classic Chlorimuron ethyl DuPont 2 Pursuit Imazethapyr SF 5 (Photosystem II Inhibitors) Glory Metribuzin DM 9 Roundup WeatherMX Glyphosate Monsanto 11 Liberty Glufosinate ayer 14 (PPO) Cadet Fluthiacet-ethyl FMC 14 Spartan Sulfentrazone FMC 14 Rumble Fomesafen DM 14 Outflank Flumioxazin DM 14 Valor SX Flumioxazin Valent 15 (Seedling Growth Inhibitor) Dual II Magnum Metolachlor Syngenta 15 Parallel Metolachlor DM 15 Zidua Pyroxasulfone SF 2 + 14 uthority XL Chlorimuron ethyl + Sulfentrazone FMC 2 + 14 Latir Imazethapyr + Flumioxazin DM 2 +14 Torment Imazethapyr + Fomesafen DM 2 +14 Valor XLT Chlorimuron ethyl + Flumioxazin Valent 2 +15 Pummel Imazethapyr + Metolachlor DM 5 + 15 Ransom Metribuzin + Flumioxazin DM 5 + 15 Tailwind Metribuzin + Metolachlor DM 14 + 15 nthem Fluthiacet-ethyl + Pyroxasulfone FMC 14 +15 Vise Fomesafen + Metolachlor DM To evaluate the effectiveness of PRE herbicides, ratings (shown in Figure 7) were taken 28 days after treatment (DT) prior to any POST applications. These ratings were averaged across both the Roundup and Liberty systems. The two principal weeds in this study were waterhemp and yellow foxtail. The waterhemp at this location has believed to be resistant to glyphosate, the active ingredient in Roundup WeatherMX. This weed population has also believed to be resistant to Group 2 (LS) herbicides such as Classic (chlorimuron-ethyl) and Pursuit (imazethapyr).
Figure 2. Classic applied PRE, 28 DT () and Pursuit applied PRE, 28 DT () Products that contained LS herbicides alone averaged 72 percent control of waterhemp 28 DT last year (Figure 7). Though Group 2 (LS) herbicides may have struggled to control waterhemp, imazethapyr (the active in Pursuit) delivered exceptional management of yellow foxtail, averaging 95 percent control at 28 DT. Glory, which contains the active ingredient metribuzin (a Group 5 herbicide), averaged 92 percent waterhemp control 28 DT when applied alone. Waterhemp control from the Group 14 (PPO) herbicides ranged from 63 to 97 percent 28 DT. However, Valor SX and Outflank (a Group 14) resulted in the greatest waterhemp control of any single mode of action. Flumioxazin, the active ingredient in Valor SX and Outflank, resulted in over 94 percent control 28 DT. Figure 3. Outflank applied PRE, 28 DT () and Glory applied PRE, 28 DT () Traditionally when we think of the Group 14 herbicides, we think of them causing injury to soybeans in cool, wet conditions (Figure 7). Group 15 herbicides such as Dual II Magnum, Parallel, and Zidua on the other hand have been believed to be safer on soybean crops during cool, wet conditions. The waterhemp control provided by Dual II Magnum and Zidua ranged from 74 to 80 percent 28 DT. The Group 15 herbicides may be safer for the crop, but they also may break down faster than a Group 14 herbicide. Overall, yellow foxtail was well controlled and the only shortcoming was Spartan 4F which resulted in 69 percent control at 28 DT. ll other PRE applications averaged more than 85 percent control of yellow foxtail 28 DT.
Figure 4. Zidua applied PRE, 28 DT () and Dual II Magnum applied PRE 28 DT () Pre-emergent herbicides were most successful at 28 DT, as shown in Figure 7. The Group 2 herbicides struggled to control waterhemp when applied alone, but their control increased when these same active ingredients were combined with another herbicide group. When chlorimuron ethyl (the active in Classic) was applied alone, the waterhemp control averaged 71 percent. uthority XL consists of chlorimuron as well as sulfentrazone (a Group 14), which is the active in Spartan 4F. When these two active ingredients were combined, waterhemp control averaged 95 percent. Valor XLT (Group 2 and 14) consists of chlorimuron ethyl(classic) plus flumioxazin, which is the active in Valor SX. Valor XLT averaged 89 percent waterhemp control 28 DT. When flumioxazin was combined with imazethapyr (Pursuit-Group 2), control increased considerably when compared to the application of imazethapyr alone. Ransom, which consists of metribuzin (Glory-Group 5) and flumioxazin (Outflank-Group 14), averaged 91 percent control of waterhemp at 28 DT. Figure 5. uthority XL applied PRE, 28 DT () and Ransom applied PRE, 28 DT () Products such as Dual II Magnum and Parallel contain the active metolachlor (Group 15) (Figure 7). Metolachlor waterhemp controlled ranged from 74% to 93% 28 DT. Tailwind consisted of the actives of metolachlor (Parallel- Group 15) and metribuzin (Glory-Group 5). s a result of using both of these active ingredients, Tailwind resulted in 92 percent control of waterhemp 28 DT. When waterhemp was treated with Pummel, a Group 2 +15 (Pursuitimazethapyr + Parallel-metolachlor) herbicide and Glory (metribuzin-group 5), control averaged 96 percent. Waterhemp control averaged 94 percent when treated with Latir (flumioxazin plus imazethapyr) with the addition of metribuzin (Group 5), versus imazethapyr applied alone (74 percent average 28 DT). To achieve greater weed control, multiple modes of action should be used as your PRE, maximizing herbicide efficacy. Figure 6. Pummel plus Glory applied PRE, 28 DT () and Latir plus Glory applied PRE, 28 DT ()
Visual Control of Pre-emergence Herbicides 28 DT 100 90 80 30 20 10 0 32 oz Tailwind @ pre 4.25 oz Latir + 6 oz Glory @ pre 10 oz Ransom @ pre 32 oz Pummel + 6 oz Glory @ pre 4 oz Valor XLT @ pre 5.5 oz uthority XL @ pre 8 oz nthem @ pre 20 oz Parallel @ pre 2.4 oz Zidua @ pre 21 oz Dual II Magnum @ pre 2.5 oz Outflank @ pre 2.4 oz Valor SX @ pre 6.8 oz Spartan 4F @ pre 0.55 oz Cadet @ pre 6 oz Glory @ pre 4 oz Pursuit @ pre 1.7 oz Classic @ pre Waterhemp Yellow Foxtail Figure 7. Visual control of waterhemp and yellow foxtail 28 DT. PRE s with multiple modes of action resulted in optimum weed control 28 DT. ut is this enough to hold back new flushes of weeds? Residuals break down over time, and that break down happens faster in wet conditions. Over the past few years at the Southern Illinois PFR site, we have experienced wet conditions which have resulted in a rapid break down of herbicides. The multiple modes of action used in the PRE applications reduced the amount of weed pressure in the POST applications. Knowing this, the next question we need to ask ourselves is, Should farmers consider a tank mix partner with their Roundup (Group 9) or Liberty (Group 11) herbicides? The answer is yes. The multiple modes of action in the POST application broadens the weed control which increases herbicide efficacy. In a Roundup system, successfully obtaining clean fields relies on multiple modes of action in both the PRE and POST applications. Some of these herbicides in Group 2 (Pursuit-imazethapyr) and Group 14 (Rumble -fomesafen) can have both PRE and POST activity. The POST activity will help control weeds that escaped the PRE, as well as provide in-season residuals. The Group 15 (Parallel-metolachlor) herbicides will reduce new weed emergence until full canopy closure with no POST activity. In the Liberty system, additional broadleaf control may not be needed. However, the addition of multiple modes of action can reduce the chance of weeds developing resistance to Liberty. So what options do you have? There are many products out there that can be applied POST and provide residual control. Some of these products have the same active ingredients that can be applied as PRE. Therefore, designing your herbicide program to ensure multiple active ingredients are applied in the PRE and POST can be a complex process. DM s Five X 5 system can help distribute these active ingredients across PRE and POST applications.
To evaluate the effectiveness of the POST treatments, final ratings were taken at harvest. POST treatments were Roundup WeatherMX or Liberty both alone or combined with other products. t harvest, waterhemp was the most prominent weed. The overall weed control was more variable in the Roundup system with treatments that had only one mode of action applied PRE (Figure 13) while the PRE applications with only one mode of action broke down before full canopy closure which allowed new flushes of waterhemp. Roundup alone was not able to control waterhemp that emerged in season after the PRE broke down. This resulted in 36 to 73 percent control of waterhemp when only a single mode of action was used in the PRE, followed by Roundup. The only exceptions to this were the products that contained flumioxazin (Group 14) such as Outflank and Valor SX, which resulted in more than 85 percent waterhemp control at harvest. Figure 8. Untreated control at harvest () and Classic followed by Roundup WeatherMX at Harvest () Herbicides with two modes of action such as a PRE followed by Roundup resulted in more than 84 percent control at harvest. The only exceptions were applications of nthem, uthority XL and Tailwind which resulted in less than 84 percent control. Three or more modes of action in the PRE plus POST applications resulted in better waterhemp control in the Roundup system (Figure 13). Using Pummel (Pursuit-imazethapyr-Group 2 + Parallel-metolachlor-Group 15) and Glory (metribuzin-group 5) followed by Roundup resulted in 83 percent control of waterhemp at harvest. When Rumble (fomesafen-group 14) was added to the POST application, the control of waterhemp increased to 99 percent at harvest. The addition of Rumble increased the total modes of action from four to five. When Rumble was substituted with Vise (Rumble-fomesafen-Group 14 + Parallel-metolachlor-Group 15) in the POST applications, waterhemp control was 100 percent. In addition, the substitution of Vise increased the number of modes of action to five. Figure 9. Pursuit followed by Roundup WeatherMX () and Parallel followed by Roundup WeatherMX () Ransom (Glory-metribuzin-Group 5 + Outflank-flumioxazin-Group 14) was one of the most effective two modes of action products in the Roundup system (Figure 13). Ransom followed by Roundup resulted in 92 percent waterhemp control at harvest. However, when Vise (Rumble-fomesafen-Group 14 + Parallel-metolachlor-Group 15) was added to Roundup, waterhemp control increased to 97 percent as a result of having four modes of action. When Pummel (Pursuitimazethapyr-Group 2 + Parallel-metolachlor-Group 15) was used instead of Vise, 97 percent waterhemp control was achieved at harvest. Though we did not see an increase in waterhemp control, the use of Vise resulted in the use of five modes of action.
Figure 10. Outflank followed by Roundup WeatherMX Figure 11. Pummel plus Glory followed by Roundup WeatherMX () and Pummel plus Glory followed by Vise plus Roundup WeatherMX () Figure 12. Ransom followed by Roundup WeatherMX () and Ransom followed by Vise plus Roundup WeatherMX ()
The use of Latir (Pursuit-imazethapyr-Group 2 + Outflank-flumioxazin -Group 14) + Glory (Group 5) followed by Roundup resulted in 86 percent control (Figure 13). The addition of Rumble (Group 14) increased waterhemp control to 99 percent from the use of four modes of action. When the Rumble was substituted with Vise (Group 14 and 15), increasing the number of modes of action to five, waterhemp control was 95 percent. Tailwind (Glory-metribuzin-Group 5 + Parallel-metolachlor-Group 15) followed by Roundup resulted in 51 percent control of waterhemp at harvest however, when Pummel was added (Pursuit-imazethapyr-Group 2 + Parallel-metolachlor-Group 15) and four modes of action were used, control increased to 99 percent. When substituting Pummel with Torment (Pursuit-imazethapyr- Group 2 + Rumble-fomesafen-Group 14) control of waterhemp decreased to 87 percent. Waterhemp Visual Ratings at Harvest in the Roundup Ready System 110 100 90 80 30 20 10 0 32 oz Tailwind fb 16 oz Torment + 32 oz RR 32 oz Tailwind fb 32 oz Pummel + 32 oz RR 32 oz Tailwind fb 32 oz RR 20 oz Parallel fb 32 oz RR 4.25 oz Latir + 6 oz Glory fb 32 oz Vise + 32 oz RR 4.25 oz Latir + 6 oz Glory fb 16 oz Rumble + 32 oz RR 4.25 oz Latir + 6 oz Glory fb 32 oz RR 10 oz Ransom fb 32 oz Pummel + 32 oz RR 10 oz Ransom fb 32 oz Vise + 32 oz RR 10 oz Ransom fb 32 oz RR 2.5 oz Outflank fb 32 oz RR 32 oz Pummel + 6 oz Glory fb 32 oz Vise +32 oz RR 32 oz Pummel + 6 oz Glory fb 16 oz Rumble + 32 oz RR 32 oz Pummel + 6 oz Glory fb 32 oz RR 6 oz Glory fb 32 RR 4 oz Valor XLT fb 32 oz RR 5.5 oz uthority XL fb 32 oz RR 8 oz nthem fb 32 oz RR 2.4 oz Zidua fb 32 oz RR 21 oz Dual II Magnum fb RR 2.4 oz Valor SX fb 32 oz RR 6.8 oz Spartan 4F fb 32 oz RR 0.55 oz Cadet fb 32 oz RR 4 oz Pursuit fb 32 oz RR 1.7 oz Classic followed by(fb) 32 oz Roundup WeatherMX (RR) Figure 13. Visual control of waterhemp at harvest in the Roundup Ready system
Overall, waterhemp control was greater in the Liberty system compared to the Roundup system. Liberty in the POST application controlled the majority of the waterhemp that escaped the PRE herbicides (Figure 16). Therefore, we saw the highest control across treatments in the Liberty system. cross treatments in the Roundup system, waterhemp control averaged 78 percent at harvest while in the Liberty system, control of waterhemp increased to 95 percent. When a single mode of action was used such as Group 2 (Classic and Pursuit), Group 5 (Glory), Group 14 (Cadet, Spartan 4F Valor SX, and Outflank) or Group 15 (Dual II and Zidua), waterhemp control ranged from 77 to 98 percent. Figure 14. Pursuit followed by Liberty () and Classic followed by Liberty () Products that contained flumioxazin once again resulted in the greatest waterhemp control, resulting in greater than 97 percent control at harvest when followed by Liberty (Figure 16). When two modes of action (nthem, uthority XL, Ransom, Valor XLT) were used in the PRE followed by Liberty, waterhemp control ranged 93 to 100 percent. When four or five modes of action were used in the Liberty system, waterhemp control never fell below 85 percent at harvest. Liberty offered a great rescue option for waterhemp control. gain, the use of more modes of action resulted in greater and more constant control at harvest Figure 15. Glory followed by Liberty () and Pummel plus Glory followed by Rumble plus Liberty ()
110 Waterhemp Visual Control at Harvest in the LibertyLink System 100 90 80 30 20 10 0 32 oz Tailwind fb + 16 oz Torment + 32 oz LL 32 oz Tailwind fb + 32 oz Pummel + 32 oz LL 32 oz Tailwind fb 32 oz Liberty 4.25 oz Latir + 6 oz Glory fb 32 oz Vise + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 20 oz Parallel + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 16 oz Rumble + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 32 oz LL 10 oz Ransom fb 16 oz Torment + 32 oz LL 10 oz Ransom fb 32 oz Pummel + 32 oz LL 10 oz Ransom fb 32 oz Vise + 32 oz LL 10 oz Ransom fb 32 oz LL 2.5 oz Outflank fb 32 oz LL 32 oz Pummel + 6 oz Glory fb 32 oz Vise + 32 oz LL 32 oz Pummel + 6 oz Glory fb 20 oz Rumble + 32 oz LL 32 oz Pummel + 6 oz Glory fb 20 oz Parallel + 32 oz LL 32 oz Pummel + 6 oz Glory fb 32 oz LL 6 oz Glory fb 32 oz LL 4 oz Valor XLT fb 32 oz LL 5.5 oz uthority XL fb 32 oz LL 8 oz nthem fb 32 oz LL 2.4 oz Zidua fb 32 oz LL 21 oz Dual II Magnum fb 32 oz LL 2.4 oz Valor SX fb 32 oz LL 6.8 oz Spartan 4F fb 32 oz LL 0.55 oz Cadet fb 32 oz LL 4 oz Pursuit fb 32 oz LL 1.7 oz Classic fb 32 oz Liberty (LL) Figure 16. Visual control of waterhemp at harvest in the LibertyLink system When it came to yield in the Roundup system, the highest yield was achieved with Pummel plus Glory PRE followed by Rumble and Roundup WeatherMX. Ransom PRE followed by Pummel and Roundup WeatherMX resulted in the lowest yield (Figure 17). In the Liberty system, Valor XLT resulted in the highest yield versus Tailwind followed by Torment plus Liberty, which had the lowest yield. The planting date may explain why we didn t see the reduction in yield with Group 14 herbicides. This test was planted in June with warmer soil conditions which reduced the potential injury. When averaged across both the Roundup and Liberty systems, the untreated check averaged 52 u./. We did not always see an increase in yield with more modes of action, however the success of your herbicide program isn t always measured by yield.
80 Yield of XL 387R4 *brand in the Roundup Ready System u./. 30 20 10 0 32 oz Tailwind fb 16 oz Torment + 32 oz RR 32 oz Tailwind fb 32 oz Pummel + 32 oz RR 32 oz Tailwind fb 32 oz RR 20 oz Parallel fb 32 oz RR 4.25 oz Latir + 6 oz Glory fb 32 oz Vise + 32 oz RR 4.25 oz Latir + 6 oz Glory fb 16 oz Rumble + 32 oz RR 4.25 oz Latir + 6 oz Glory fb 32 oz RR 10 oz Ransom fb 32 oz Pummel + 32 oz RR 10 oz Ransom fb 32 oz Vise + 32 oz RR 10 oz Ransom fb 32 oz RR 2.5 oz Outflank fb 32 oz RR 32 oz Pummel + 6 oz Glory fb 32 oz Vise +32 oz RR 32 oz Pummel + 6 oz Glory fb 16 oz Rumble + 32 oz RR 32 oz Pummel + 6 oz Glory fb 32 oz RR 6 oz Glory fb 32 RR 4 oz Valor XLT fb 32 oz RR 5.5 oz uthority XL fb 32 oz RR 8 oz nthem fb 32 oz RR 2.4 oz Zidua fb 32 oz RR 21 oz Dual II Magnum fb 32 oz RR 2.4 oz Valor SX fb 32 oz RR 6.8 oz Spartan 4F fb 32 oz RR 0.55 oz Cadet fb 32 oz RR 4 oz Pursuit fb 32 oz RR 1.7 oz Classic followed by(fb) 32 oz Roundup WeatherMX (RR) Yield of ECK 394L4brand in the LibertyLink System 80 30 20 10 0 32 oz Tailwind fb + 16 oz Torment + 32 oz LL 32 oz Tailwind fb + 32 oz Pummel + 32 oz LL 32 oz Tailwind fb 32 oz Liberty 4.25 oz Latir + 6 oz Glory fb 32 oz Vise + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 20 oz Parallel + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 16 oz Rumble + 32 oz LL 4.25 oz Latir + 6 oz Glory fb 32 oz LL 10 oz Ransom fb 16 oz Torment + 32 oz LL 10 oz Ransom fb 32 oz Pummel + 32 oz LL 10 oz Ransom fb 32 oz Vise + 32 oz LL 10 oz Ransom fb 32 oz LL 2.5 oz Outflank fb 32 oz LL 32 oz Pummel + 6 oz Glory fb 32 oz Vise + 32 oz LL 32 oz Pummel + 6 oz Glory fb 20 oz Rumble + 32 oz LL 32 oz Pummel + 6 oz Glory fb 20 oz Parallel + 32 oz LL 32 oz Pummel + 6 oz Glory fb 32 oz LL 6 oz Glory fb 32 oz LL 4 oz Valor XLT fb 32 oz LL 5.5 oz uthority XL fb 32 oz LL 8 oz nthem fb 32 oz LL 2.4 oz Zidua fb 32 oz LL 21 oz Dual II Magnum fb 32 oz LL 2.4 oz Valor SX fb 32 oz LL 6.8 oz Spartan 4F fb 32 oz LL 0.55 oz Cadet fb 32 oz LL 4 oz Pursuit fb 32 oz LL 1.7 oz Classic fb 32 oz Liberty (LL) Figure 17: Yield of XL 387R4 *brand () and ECK 394L4brand ()
When averaged across treatments in a Roundup system, the use of five modes of action resulted in up to a 2 u./. increase (Figure 18). In the Liberty system, the use of two modes of action resulted in up to a 1 u./. increase in yield when averaged across treatments. With more modes of action, we tend to see a variation or decrease in yield. However, we must remember the benefits are not shown with a yield monitor, but by limiting the deposit of new seed to the soil seed bank. Yield y Number of Modes of ction in the Roundup Ready and LibertyLink Systems 65 XL 387R4 * brand ECK 394L4 u./. 55 45 Two Three Four Five Two Three Four Five Number of Modes of ction In this study, broader weed control was achieved with multiple modes of action and more active ingredients. In the Roundup system, waterhemp was more difficult to control than in the Liberty system, however waterhemp control could still be achieved if more modes of action were used. In the Liberty system, waterhemp could be controlled POST with Liberty, but we must not fall into this trap if we want Liberty to remain effective. Though multiple modes of action in the PRE is crucial to both systems, this may not be enough for season-long weed control. Using more modes of action in the POST application can help reduce the number of escapes in both the Roundup and Liberty applications. Using more active ingredients that are effective will help reduce the selection process of one herbicide active ingredient such as Liberty alone. POST products help increase POST control and some may provide an in-season residual. In both systems we have seen the benefit of POST application with an in-season residual as well as POST products. Though some of these active ingredients are older chemistry, when strategically placed they resulted in optimum weed control. We may not always see a positive return in yield. However, from a weed management point of view there is a positive increase in weed control. Joe olte Southern Illinois PFR Operator Figure 18. Yields by number of modes of action in Roundup Ready and LibertyLink systems Practical Farm Research (PFR) is a registered trademark of eck s Superior Hybrids. XL is a registered trademark of Pioneer. XL brand seed is distributed by eck s Superior Hybrids, Inc. LibertyLink and Liberty are registered trademarks of ayer. Roundup, Roundup Ready and Roundup WeatherMX are registered trademarks of Monsanto Technology, LLC. Pursuit and Zidua are registered trademarks of SF. uthority XL, nthem, Cadet and Spartan 4F are trademarks of FMC Corporation. Classic is a registered trademark of E. I. du Pont de Nemours and Company. Glory, Parallel, Pummel, Ransom, Rumble, Latir, Tailwind, Torment, Vise and Outflank are trademarks of Makhteshim gan of North merica, Inc. Valor SX and Valor XLT are registered trademarks of Valent U.S.. Corporation. Dual II Magnum is a registered trademark of a Syngenta Group Company.