14 C.F.R. § 137.39
(a) Except as provided in paragraph (b) of this section, no person may dispense or cause to be dispensed from an aircraft, any economic poison that is registered with the U.S. Department of Agriculture under the Federal Insecticide, Fungicide, and Rodenticide Act (7 U.S.C. 135-135k)—
(b) This section does not apply to any person dispensing economic poisons for experimental purposes under—
[Amdt. 137-2, 31 FR 6686, May 5, 1966]