Agglomerated corncob fines have been proposed by the primary supplier of ground corncob, as an additive toground corncob for use as a granular pesticide carrier, but how much agglomerated corncob product can be added withoutchanging spreader rate or pattern performance is not known. Pesticide formulations on plain corncob and cob amended with5, 10, and 20% agglomerated cob material were evaluated for pattern and rate effects in three homeowner rotary spreadersand for rate effects in three homeowner drop spreaders. Two of the three rotary spreaders had differences in pattern skewing.Rate changes due to material were noted with five of the six spreaders, but changes were not consistent with the percentageof agglomerated material added. It is necessary to test each formulation using agglomerated corncob additive to determinewhether setting changes will be required on the product labels.