Synergism Synergists are usually combined with insecticides in ratios from 2:1 to 10:1 (synergist to insecticide). In the presence of a synergist,a little active ingredient can go a long way. Synergism Synergists are usually combined with insecticides in ratios from 2:1 to 10:1 (synergist to insecticide). In the presence of a synergist In the presence of a synergist, a little active ingredient can go a long way