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Oxalic Acid FAQ's
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Information on the Upcoming Amendment to the Varroacide, Oxalic Acid (API-Bioxal)

USDA and EPA are receiving questions from stakeholders regarding a recent tolerance exemption for oxalic acid, a pesticide used to control parasitic mites of honey bees (Apis mellifera). A tolerance is the legal limit for a chemical residue in or on a food. The in-hive use of oxalic acid to control Varroa mites (Varroa destructor) is currently a USDA-held registration. Frequently asked questions by stakeholders include when the product can be legally applied, whether this is an exemption from EPA registration, and how existing stock(s) of oxalic acid can be used moving forward. With this it is important for beekeepers to understand that the registration and legal use of oxalic acid in the U.S. for in-hive use is currently only through the registered product API-Bioxal™ (of which oxalic acid is the active ingredient).

Varroa mites were introduced into the U.S. in 1987 and have become a major factor affecting honey bee health and survival, and there is a critical need for effective Varroa control tools that can be used in an integrated pest management approach. The Environmental Protection Agency (EPA), U.S. Department of Agriculture (USDA), and USDA partner the Interregional Research Project 4 (IR-4)—with support from the University of Georgia and Auburn University—have worked to expand the current oxalic acid dihydrate label (EPA Registration Number 91266-1) for the control of Varroa mites in managed honey bee colonies. API-Bioxal™ (EPA Registration Number 91266-1-73291) is currently the only legally registered oxalic acid dihydrate product in the United States that can be used to treat varroa mites.

In the near future, the current label for oxalic acid (i.e., API-Bioxal™) use in bee colonies to control varroa mites will be amended (expanded), as described herein, to allow for the application of oxalic acid (API-Bioxal™) year-round, including when honey supers are in place. Allowable application methods and application rates will not change. The first step in this expansion process has taken place, with EPA issuing a tolerance exemption on February 23, 2021, as announced in the Federal Register. A tolerance (i.e., the legal limit for a pesticide chemical residue in or on a food) is issued under the Federal Food, Drug and Cosmetic Act (FFDCA); FFDCA allows EPA to establish an exemption from the requirement for a tolerance if EPA determines with reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue. As discussed in the Federal Register notice, EPA was able to meet the requirements stipulated under the FFDCA to exempt oxalic acid from a tolerance.

Oxalic acid is ubiquitous in the environment, found naturally in many plants and vegetables, as well as in honey. It occurs naturally as the potassium or calcium salt in plant sap, notably in plants of the Oxalis and Rumex families. It can be a considerable constituent of the dry weight of some plants, such as beet leaves, cocoa, tea, spinach, rhubarb, and chard.

Oxalic acid (API-Bioxal™) is still registered under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and its application must adhere to EPA label requirements. The oxalic acid (API-Bioxal™) label is currently undergoing amendments by EPA to expand the in-hive use to year-round. Use of oxalic acid that does not adhere to what is specified on the label or use of an unregistered source of oxalic acid (that is not a registered EPA product) is considered an “off-label” use and is subject to EPA enforcement under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).

Frequently Asked Questions:

  1. When can I start applying oxalic acid (API-Bioxal™) in my hives when honey supers are on?

The label amendments expanding the in-hive use to year-round are still being finalized. Oxalic acid (API-Bioxal™) cannot be applied in hives when honey supers are on until the amended label or a supplemental label is provided on the product. USDA is pursuing a supplemental label to ensure that beekeepers can begin using this product legally when honey supers are on as soon as possible. However, beekeepers can only legally begin using this product year-round once a supplemental label and/or the new amended label is included with the product packaging.

  1. What products can I use to apply oxalic acid to my honey bee colonies?

Oxalic acid dihydrate can only be applied to colonies legally using API-Bioxal™ (EPA Registration Number 91266-1-73291). It is currently the only EPA-recognized oxalic acid product for in-hive use and the only way a beekeeper can apply oxalic acid to their colony for varroa mite control. The use of wood bleach, oxalic-acid rich plants, or oxalic acid from chemical supply companies are not registered products. Use of oxalic acid that does not adhere to label requirements or that is not an EPA-recognized product is considered a label violation and is subject to enforcement under FIFRA.

  1. I have existing stocks of EPA-registered oxalic acid (API-Bioxal™) product. Can it be used when honey supers are on or must I adhere to the label that was included with the product when it was purchased?

No, users of oxalic acid (API-Bioxal™) must adhere to the label supplied with the product. That is, oxalic acid (API-Bioxal™) cannot be used when honey supers are on unless specified on the EPA-approved product label or supplemental product label. Use of oxalic acid that does not adhere to what is specified on the label would be considered a violation and is subject to enforcement under FIFRA.

  1. Once the amended label is approved by EPA, can I print a copy of the new label and use the product legally?

No. The amended label must be supplied when the product is purchased to use the product legally.

  1. Does this mean I can apply oxalic acid (API-Bioxal™) using different application methods or application rates than those that are currently on the label?

No. Use of application methods or application rates that differ from those specified on the label would be considered a violation and is subject to enforcement under FIFRA. Currently, the only allowable application methods are a solution method, spraying package bees, and using a vaporizer method. Determining which method is best depends on your colonies, past experience, and mite loads. USDA recommends that you consult with apiary inspectors in your area for additional information. Use of oxalic acid that does not adhere to what is specified on the label would be considered a violation and is subject to enforcement under FIFRA. Further, off-label patterns of use may be detrimental to the user, honey bees, the environment, and products of the hive.

  1. What is the limit in the number of consecutive treatments I can do annually?

At this time, the current label does not specify a maximum number of applications that can be made per year.

  1. Why is the label so vague about how I can treat with OA and how often and at what day time temperatures I should use it?

USDA and EPA believe that the product can be used effectively throughout the year without further limitations. When oxalic acid dihydrate was evaluated by EPA for in-hive use to control varroa, the evaluation was conducted based on the proposed label and consistent with data that had been previously used to support the active ingredient’s use in other countries. If there are indications through incident reports that current label-specified use parameters are insufficient as evidenced by adverse effects to applicator and/or non-target organisms (e.g., bees), the EPA would consider additional mitigation to ensure that use of the product meets the FIFRA standard.

  1. How much oxalic acid (API-Bioxal™) could be in the honey if using this product when honey supers are on?

At this time, the EPA has determined that the quantity of oxalic acid (API-Bioxal™) in the honey is not expected to exceed levels that naturally occur in various products in consumer diets. That amount likely varies depending on the plant just as levels in honey will depend on floral nectar sources; therefore, the specific concentration cannot be readily specified.

  1. Will the honey label have to be changed to show that it may contain oxalic acid crystals?

As indicated in the Federal Register Notice, EPA determined that oxalic acid residues in honey resulting from the use of the product when honey supers are in place would be not be substantially different to other naturally occurring products which also do not contain hazard statements regarding oxalic acid crystal formation. If incident data become available to suggest adverse or unexpected effects from the registered use of a product, then those data will be considered by EPA in determining whether advisory and/or more restrictive language is needed on the label.

  1. Does vaporizing colonies in the summer affect honey bees? 

If there are documented adverse effects on bee colonies resulting from the registered use of oxalic acid (API-Bioxal™) and these incidents have been reported to the EPA, they will be considered in determining whether additional advisory and/or compulsory statements need to be added to the label.  

  1. Are any other aspects of the oxalic acid (API-Bioxal™) label changing?

Yes. Clarifications are being made throughout the label. Additionally, Personal Protective Equipment (PPE) requirements have also been updated, such as wearing a minimum of a NIOSH-approved particulate filtering facepiece respirator with any N, R, or P filter when applying solution methods and wearing a minimum of a NIOSH-approved elastomeric half mask respirator with acid gas cartridges and combination N, R, or P filters when applying the product by the vaporizer method.

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