SUPPLEMENTARY INFORMATION:

The Animal and Plant Health Inspection Service (APHIS) has prepared a final environmental assessment (EA) and finding of no significant impact (FONSI) relative to the field release of the blister mite, Aceria salsolae (Acari: Eriophyidae), for the biological control of Russian thistle ( Salsola tragus L.) within the contiguous United States. The action will reduce the severity of infestations of Russian thistle in the central and western United States. After completion of the environmental analysis, APHIS will issue permits for the release.

Russian thistle, or tumbleweed, is an alien weedy annual plant that infests about 41.3 million hectares (100 million acres) in the western United States. It is native to the mountainous regions of southwest Asia and was accidentally first introduced in the early 1870s in South Dakota. Since then, it has spread over most of the central and western United States and southern Canada. It grows primarily in fallow or disturbed soil, along roadsides and irrigation canals, and in waste areas in arid and semiarid zones. Russian thistle is listed as a noxious weed in five states and causes millions of dollars in damage by disrupting automobile traffic, clogging irrigation canals, displacing native plant species, providing habitat to insect pests of many fruits and vegetables, and is highly flammable, contributing to a rapid spread of wildfires.

Permitting the release of A. salsolae in the contiguous United States is likely to help control invasive Russian thistle. A. salsolae is a recently discovered eriophyid mite species. Mite species are usually extremely host specific and therefore generally pose low risk to nontarget plants, making them a likely candidate for classical biological control of weeds. A. salsolae has been reported only from S. tragus and is the only eriophyid mite collected from these plants. A. salsolae causes severe damage to the plant by feeding on epidermal cells in the meristematic tissue, stunting growth and preventing development of branches and flowers needed for reproduction. Host-specificity testing indicates A. salsolae is unlikely to attack non-target species.

Russian thistle is very difficult to control because current chemical ( i.e., herbicides), mechanical ( i.e., tilling), and cultural ( i.e., competition from a healthy, well-watered crop) controls are not effective against this widespread weed. However, Russian thistle is an excellent target for classical biological control ( i.e., use of exotic natural enemies) because it has no close taxonomic relatives in North America. Classical biological control is a potentially useful management strategy for an invasive pest species whenever effective resident natural enemies are lacking in the new distribution range.

On March 10, 2009, APHIS published a notice of availability of a draft EA ^[1] in the Federal Register (74 FR 10223-10224, Docket No. APHIS-2008-0143). APHIS explained in the draft EA that after reviewing host specific testing of 39 species and 12 varieties of host plants from five (5) families, including 25 native species of North America, A. salsolae was not expected to directly harm any plants outside of the targeted Russian thistle and there was no population increase of A. salsolae on nontarget plant species. The draft EA was made available to the public for a 30-day comment period. However, because of a comment APHIS received on the draft EA raising concerns about the release of A. salsolae, APHIS did not issue a finding of no significant impact (FONSI) and also did not issue permits allowing the environmental release of A. salsolae. The commenter was concerned about some additional testing conducted by the permit applicant that indicated that A. salsolae mites survived for at least five (5) weeks on five non-target plants. In the intervening years since publication of the draft EA, additional research has been conducted providing new host specificity information that enabled APHIS to strengthen its support for the release of A. salsolae within the contiguous United States for classical biological control of Russian thistle. Due to the availability of this additional research, we revised the prior draft EA and made the revised draft EA available to the public for a second round of public comments.

On June 27, 2025, we published in the Federal Register (90 FR 27522-27523, Docket No. APHIS-2024-0040) a notice ^[2] in which we announced the availability, for public review and comment, of a revised draft EA that examined the potential environmental impacts associated with permitting the release of the blister mite, A. salsolae, for the biological control of Russian thistle within the contiguous United States. Comments on the notice were required to be received on or before July 28, 2025. We received three (3) comments on the revised draft EA by ( printed page 58400) that date all of which were supportive of the environmental release of the blister mite, A. salsolae, for the biological control of Russian thistle within the contiguous United States. One commenter recommended APHIS coordinate the field release with other Federal land management agencies to ensure the field release can occur on all affected public lands. We have revised the final EA, where appropriate, and our full response to comments can be found in Appendix 3 of the final EA.

In this document, we are advising the public of the availability of the final EA and our FONSI regarding the field release of blister mite, Aceria salsolae De Lillo and Sobhian (Acari: Eriophyidae), for the biological control of Russian thistle ( Salsola tragus L.) within the contiguous United States. Based on the analysis in the final EA, APHIS determined that the field release of A. salsolae for the biological control of Russian thistle within the contiguous United States will not have a significant impact on the quality of the human environment. As a result of this finding, we will issue permits for the field release A. salsolae for the biological control of Russian thistle within the contiguous United States.

The final EA and FONSI may be viewed on the Regulations.gov website (see footnote 1). Copies of the final EA and FONSI are also available for public inspection at Room 1620 of the USDA South Building, 14th Street and Independence Avenue SW, Washington, DC. Normal reading room hours are 8 a.m. to 4:30 p.m., Monday through Friday, except holidays. Persons wishing to inspect copies are requested to call ahead at (202) 799-7039 to facilitate entry into the reading room. In addition, copies may be obtained by calling or writing to the individual listed under FOR FURTHER INFORMATION CONTACT .

The final EA and FONSI have been prepared in accordance with: (1) The National Environmental Policy Act of 1969 (NEPA), as amended (42 U.S.C. 4321-4370m-11); (2) the former regulations of the Council on Environmental Quality for implementing the procedural provisions of NEPA (40 CFR parts 1500-1508) as of February 25, 2021; (3) U.S. Department of Agriculture regulations implementing NEPA (7 CFR part 1b) effective through July 2, 2025; and (4) APHIS' NEPA Implementing Procedures (7 CFR part 372) effective through July 2, 2025.

91 FR 58399