Nov. 21, 2015

The following guest article is by Craig Romary, environmental program specialist, and Tim Creger, pesticide program manager, for the Nebraska Department of Agriculture; and Mike Kucera, agronomist, NRCS National Soil Survey Center, Soil Quality and Ecosystems Branch

Once a pesticide is used in a cropping system, the restrictions on the label must be followed for the original crop it is used on, and any succeeding crops, until all restrictions on that label have been met. One of these is called the plant-back restriction. Plant-back restrictions exist for two reasons:

1. To avoid carryover pesticide injury to the subsequent crop (such as with herbicides).
2. To protect humans and livestock from elevated levels of pesticide residues that a succeeding crop may accumulate.

Because cover crops are re-emerging as an important practice for conserving soil, increasing soil water, and improving soil health and function, one needs to be aware of these restrictions and include them in the planning process. However, many of the plant species used in today's cover crop mixtures may not be specifically listed on the label to ensure establishment of the stand or the safety of the feed or forage.  The following points highlight scenarios that may affect what is planted for cover crops and how they are used.  Cover crops serve different purposes than forage crops although they may actually be the same species or mixture. The crop's end purpose — either cover or forage — affects plant-back and forage/harvest restrictions.

Cover crops are planted before or after harvest of the cash crop, where the cover crop will not be grazed or harvested for forage. It is acceptable to plant cover crop species, as long as the pesticide label does not specifically list plant-back restrictions for the cover crop species, or is silent on the cover crop species (not listed on the label). Some pesticide labels will list crop groups rather than specific crop species.

Forage crops are planted before or after harvest of the cash crop, where the crop will be utilized for grazing or as forage for livestock whose meat, milk, or other products will be marketed. If the pesticide label has any of the following, it is an obvious violation of pesticide laws when a prohibited cover species is planted or grazed/harvested for forage within that time:

• specific plant-back restrictions for the crop species;
• prohibitions against grazing/harvesting forage; or
• limits on grazing/harvesting forage within a certain time following a pesticide application.

The absence of any particular forage/cover crop species on the pesticide label does not mean those plant species can be legally grown, harvested, or consumed by animals.

More Information

Specific questions on planting, grazing, or haying forage/cover crops should be directed to the pesticide registrant, because the registrant is the one required to submit residue data to EPA for registration purposes.  Regulatory questions can be directed to the lead agency in your state for pesticide regulations (see national directory). In Nebraska contact the Nebraska Department of Agriculture's Animal and Plant Health Protection focus area at 402-471-2351.

Resources for the growers, pesticide applicators, and crop consultants:

• UNL's Guide for Weed Management in Nebraska with Insecticide and Fungicide Information contains tables on Replant Options and Rotation Restrictions, and Forage, Feed and Grazing Restrictions for Row Crop Herbicides.
  
  Note, however, that the table on forage, feed and grazing restrictions is directed toward foraging, feeding, and grazing of the crop the pesticide was applied to, not a cover/forage crop planted after the cash crop.
   
• University of Wisconsin's Herbicide Rotation Restrictions in Forage and Cover Cropping Systems

Always read and follow label directions for these and other restrictions.