This rule extends a time-limited tolerance for residues of the insecticide and miticide avermectin B1 and its delta-8,9-isomer in or on spinach and celeriac at 0.05 part per million (ppm) for an additional 18 month period, to January 31, 2000. This action is in response to EPA's granting of an emergency exemption under section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizing use of the pesticide on spinach and celeriac. Section 408(l)(6) of the Federal Food, Drug, and Cosmetic Act (FFDCA) requires EPA to establish a time-limited tolerance or exemption from the requirement for a tolerance for pesticide chemical residues in food that will result from the use of a pesticide under an emergency exemption granted by EPA under section 18 of FIFRA.