Happy New Year! Here’s a New Year’s poem/resolution to get you started this year:

Pigweeds are red,

Kochia is too,

I’ll control these weeds,

How about you?

Soybean varieties will be available in 2019 that contain both Liberty Link® and RoundUp Ready® traits. This will provide much more flexibility with herbicide programs and should result in much cleaner fields when glyphosate-resistant weeds are present. The system will require some additional training. Previous studies have demonstrated antagonism between the two products when tank-mixed. We conducted a study at the CREC last season to test different rates and adjuvants with the two products. Application conditions were designed to optimize the Liberty application since it is the more expensive product (i.e. we used 15 GPA). Here is what we learned (Table 1).

Table 1. RoundUp and Liberty combinations for controlling common ND weeds

Assessments in Table 1 were taken 14 days after the herbicide application. In some cases we did identify antagonism, particularly when using 28 fl oz of RoundUp Powermax. Better weed control was achieved at times by using 21 fl oz of RoundUp Powermax when mixed with Liberty. Even when there was no antagonism between the products, there was never an advantage to mixing the products where the combination performed better than either product alone. Essentially, mixing the products would be a waste of money.

Proper stewardship and economics dictate that these two products should be applied separately. Consider the following in-crop sequence for applications: Use Liberty as an early POST treatment to be as effective as possible on small broadleaf weeds (with or without an approved tank-mix partner). Follow-up with a mid-season application of glyphosate (+ tank-mix partner). And of course, your foundation PRE herbicide program will ultimately determine the long-term success of your POST applications. 

Mike Ostlie, Ph. D.
Mike.Ostlie@ndsu.edu
Research Agronomist