Exponent Insecticide Synergist should be mixed 0.8 oz. per gallon of water.
Yes, adding Exponent Insecticide Synergist to Bifen IT will give you a faster initial knockdown only. Once dry only the residual of Bifen IT will be left behind to keep killing insects.
Exponent Insecticide Synergist would offer a faster initial knockdown of those insects out in the open during application when tank mixed with an insecticide. Since there is no residual, it would not affect the Tandem.
Exponent Insecticide Synergist is only a synergizing agent and by itself, will not actually be able to kill insects. For control of spiders, including black widows, we recommend a product such as Onslaught FastCap.
Yes, you can mix Exponent Insecticide Synergist with Bifen IT.