We don’t often write an eUpdate article when a new herbicide is approved by the Environmental Protection Agency (EPA). However, last week, the EPA issued a final decision to approve Liberty Ultra (glufosinate-P), making it the first herbicide with a label for agronomic crops that follows the principles outlined in the EPA’s Herbicide Strategy, which is intended to help herbicide registrations comply with Endangered Species Act requirements. You can learn more about the Herbicide Strategy in this recent War Against Weeds podcast. While this language will vary among products, the Liberty Ultra label provides somewhat of a template for what we should expect going forward. Specifically, the new language pertains to reducing off-target herbicide movement and pesticide use limitation areas (PULAs).

Key aspects of the Liberty Ultra label that pertain to reducing off-target movement are included in Table 1. Changes from the Liberty 280 SL label are indicated in bold.

All herbicides will require runoff mitigation points. The number of points required will vary for each herbicide. Mitigation options/practices are described in the EPA’s Mitigation Menu. Key aspects of the mitigation menu are summarized in Table 2. The EPA has developed a runoff points calculator that can help determine the number of points earned for practices already in place on your fields, including a ‘credit’ for certain counties that have relatively less runoff vulnerability. Table 3 lists the runoff mitigation relief points assigned to Kansas counties.

Table 1. Some examples of Liberty Ultra label requirements intended to reduce off-target herbicide movement.

¹ Predicted wind speed and direction for the application site should be acquired within 12 hours prior to application and should be reassessed every 15 minutes during the application.Measuring wind speed and direction can be done by: instruments on the application equipment, anemometer, windsock, aircraft smoke system, checking behind spray rig.²Spray drift buffers can include: Agricultural fields, roads, mowed grassy areas, bare ground, man-made structures with walls and/or a roof, vegetative filter strips, hedgerows, CRP lands, other items on the mitigation menu, provided herbicide does not degrade CRP habitat, managed wetlands, on-farm irrigation water resources not connected to adjacent water bodies.³Windbreak or shelterbelt for 100% reduction with ground application must: run the full length of the treated area with no significant breaks; be sufficiently dense such that the non-managed area is not visible at the time of application; be planted according to conservation program standards and not include federal noxious species⁴Windbreak of shelterbelt for 50% reduction with aerial application must: meet criteria for ground application plus: trees must be the same height or above the release height of the application; have a minimum of 1 row of trees/shrubs or a 4 ft wide strip of non-woody vegetation. A semi-permeable manmade structure can also be used.Windbreak or shelterbelt for 75% reduction must: meet criteria for ground application plus: be at least twice as high as the release height of the application; have a minimum of 2 rows of trees/shrubs or at least 8 ft of non-woody vegetation.⁵Runoff mitigation is not required if the field has: a perimeter berm system, an irrigation tailwater return system, subsurface or tile drains with a water control structure and controlled outlet; or if the application is: an injection, applied subsurface or under plastic mulch, a spot treatment, less than 1/10 of an acre; or if all areas within 1,000 ft down-slope are managed.⁶Points assigned to various mitigation options are listed in Table 2. The number of points required will vary for each herbicide.

Table 1. Summary of Runoff/erosion mitigation measures and associated points. Applicators will be required to document how needed points are accrued for each application.

⁷County-based mitigation relief points for Kansas counties are listed in Table 3. National information is available online in a list or map format.⁸A runoff/erosion specialist is someone who has technical training, education, and/or experience in an agricultural discipline, water or soil conservation, or another relevant discipline that provides training and practice in the area of runoff or erosion mitigation and participates in continued education or training in those areas and has experience advising on conservation measures listed on the EPA’s mitigation website. Includes NRCS staff, Certified TSPs CCAs, CPAg, NAICC members, and Extension agents

Table 3. Runoff and erosion mitigation points assigned to Kansas counties based on runoff/erosion vulnerability.