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Pre-Emergent Herbicide Study - Don’t want it, treat it like you already have it!

Pre-emergent herbicides were put to the ultimate test during last growing season.

BECK’S Pre-Emergent Herbicide Study - 2014
Using pre-emergent herbicides allow growers an early start on their weed control in order to gain optimum yield potential. This study was designed to test multiple pre-emergent herbicides with a wide range of weed control. All products were applied immediately after planting on May 7th.
All of our pre-emergent herbicides were put to the ultimate test this growing season. Due to 3.7 inches of rain and 40-50 degree temperatures at emergence, we were left with just under 50% of our planted population. The combination of standing water and below average temperatures was the starting point for optimum disease and herbicide injury. Significant amounts of phytophthera and pithium, as well as, ALS and PPO injury were found throughout this year’s study. With the excessive amount of rainfall, most residual compounds did not hold up as long as in years past. With the variable stands in the plot, our main focus was to scout and document final populations and weed pressure early in the growing season. The product description and performance reviews for each product can be found below. All descriptions list the active ingredients and their respective modes of action (effect on plant growth). All photographs were taken three weeks after planting (May 28th, 2014).
The control received no pre-emergent herbicides. After seven weeks with no herbicides, we were starting to see more weeds than soybeans. Some of the main weeds include marestail, lambsquarter, common ragweed, velvetleaf, pigweed, purslane, and multiple grass species. With those adverse weather conditions at planting and the heavy weed pressure, our final population was around 85,000 plants/A.
Boundary herbicide delivers early season grass and broadleaf weed control, excellent resistance management and rotation flexibility. The two active ingredients in Boundary are S-metolachlor and Metribuzin. S-metolachlor is a seedling shoot growth inhibitor while Metribuzin is a photosynthesis inhibitor. During the first four weeks, there were minimal grass escapes with the use of Boundary herbicide, but at the fifth week we started to see a few grass species and broadleaves emerge, mainly velvetleaf and pigweed. Overall, Boundary had good grass control, but wasn’t able to keep the heavy broadleaf pressure from emerging. In terms of final stands, Boundary had the highest, other than the control. We feel this was mainly due to the fact that Boundary does not include a PPO herbicide.
Valor XLT herbicide offers a broad spectrum broadleaf residual control of tough weeds with two proven modes of action. The two active ingredients in Valor XLT are Flumioxazin and Chlorimuron. Flumioxazin is a cell membrane disrupter while Chlorimuron is an amino acid synthesis inhibitor. With the one two punch Valor XLT offers, it proved to keep both replications broadleaf free for the eight week period before the post herbicide application was made. Multiple grass species were identified after the first three weeks. Valor XLT was the top-performing PPO herbicide used in terms of final populations as well as return on investment.
Authority® XL can be applied in the spring to control tough weeds like marestail, waterhemp, lambsquarters and ragweed. The two active ingredients in Authority XL are Sulfentrazone and Chlorimuron. Sulfentrazone is a cell membrane disruptor while Chlorimuron is an amino acid synthesis inhibitor. Similar to Valor® XLT, Authority XL was able to keep both replications broadleaf free for the eight week period before the post herbicide application was made. However, grass was less of an issue with the use of Authority XL when compared to Valor XLT. Authority XL was one of the best herbicides tested in the 2013 Pre-Emergent Herbicide Study and proved itself as a top performer once again in 2014.
Fierce® XLT provides one of the broadest weed control packages available for small and large-seeded broadleaves (including ragweeds), as well as annual grasses. Fierce XLT is one of two products tested in this year’s study that provides three modes of action. The three active ingredients in Fierce XLT are Flumioxazin, Pyroxasulfone, and Chlorimuron. Flumioxazin is a cell membrane disrupter, Pyroxasulfone is a seedling shoot growth inhibitor, and Chlorimuron is an amino acid synthesis inhibitor. With the triple modes of action Fierce XLT provides, we were left with zero broadleaf escapes and minimal grasses for the eight week period. Last year we tested Fierce and didn’t see a single weed escape all year long. With the increased weed pressure and added weather extremities of the 2014 growing season we were more than pleased with the added performance of Fierce XLT.
Authority® MTZ is a flexible herbicide that can be used as part of a fall burndown program to control winter annuals and other broadleaf weeds. It can also be used as a pre-emergent herbicide for soybeans. The two active ingredients in Authority MTZ are Sulfentrazone and Metribuzin. Sulfentrazone is a cell membrane disrupter while Metribuzin is a photosynthesis inhibitor. We saw similar results with Authority MTZ as we did with Authority XL. We did observe a little heavier grass pressure escape around five weeks after application. Even though our return on investment wasn’t as high as some of the other herbicides, we were still able to gain $7.76/A from the use of Authority MTZ.
Authority® Maxx provides maximum residual control of small seeded broadleaf weeds, Waterhemp and Palmer Amaranth, in particular. Authority Maxx also provides the most affordable residual control of any other product in the Authority lineup. Authroity Maxx is compromised of the same two active ingredients that are in Authority XL. The only differences between the two herbicides are the ratio of each active ingredient and price. Authority Maxx was one of the top performers of the year in terms of long-lasting broadleaf control. However, it has one of the highest rates of PPO used in this year’s study. This led to slightly higher stand loss than some of the other products tested. Overall, Authority Maxx was able to keep weed pressure to a minimum with excellent broadleaf resistance control. Furthermore, if resistant weeds like Waterhemp and Palmer Amaranth are a challenge, Authority Maxx is a good choice for you.
OpTill PRO® herbicide delivers three overlapping sites of action, giving soybean growers preplant and pre-emergence management of tough-to-control weeds. Powered by Kixor® herbicide technology, it provides fast, broad-spectrum burndown and enhanced residual control. The three active ingredients in OpTill PRO are Saflufenacil, Imazethapyr, and Dimethenamid-P. Saflufenacil is a cell membrane disrupter, Imazethapyr is an amino acid synthesis inhibitor, and Dimethenamid-P is a seedling shoot growth inhibitor. OpTill PRO was most impressive with the residual control it was able to offer regardless of the adverse conditions. Overall, it had the least number of weed escapes regardless of species, however, the stand loss was so significant that we did not receive a return on investment from the use of OpTill PRO in 2014. We would like to do more testing with 
OpTill PRO because we know the weed control performance exceeded our expectation, but the potential for plant injury needs continued analysis.
Overall, the 2014 growing season was an excellent opportunity for us to test different pre-emergent herbicides. Being able to evaluate not only weed control and residual longevity but also potential herbicide injury effects made it a researcher’s dream. Even with the excessive PPO injury we encountered this year, it is still more important than ever to rotate chemistries and take advantage of these and many other great products. In terms of weed resistance: if you don’t want it, you must treat it like you already have it.
Beck's Hybrids PFR program conducts more than 75 different studies across multiple locations (500+ acres) to learn how different management practices and new technologies perform in field environments. Simply put, it is research focused with the farmer in mind.

To see the entire study, please download the PFR Book and see page 85
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