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The impact of an experimental aerial application of carbaryl (Sevin-4-oil®) on the macroinvertebrate fauna of woodland ponds was studied in northern Maine. Carbaryl was applied at the rate of 840 g A.I./ha, the same rate as was used for control of spruce budworm, Choristoneura fumiferana (Clemens), damage. Four treated ponds and three untreated ponds were observed for up to 30 months following treatment. Maximum residue levels of 254 μg/L were found in the water and 53,793 μg/kg (dry weight) in the sediment. Residues were detectable in the water 14 months and in the sediment 16 months after treatment.The most severe and persistent impact was on the Amphipoda with Hyallela azteca (Saussure) and Crangonyx richmondensis Ellis reduced to near 0/m2 and failing to recolonize in some of the ponds 30 months after treatment. Numbers of immature Ephemeroptera and Trichoptera were reduced immediately following spray application but this impact did not persist throughout the season nor into the following year. Immediate reduction in numbers of adult Ephemeroptera and Trichoptera emerging from the ponds was also found. Numbers of immature Odonata were reduced following treatment and remained low during the following year. The Chironomidae did not appear affected either as immatures or emerging adults.