What’s the difference?

Pyrethrum is the name of the plant in the chrysanthemum family and the name used to describe the insecticidal goo extracted from it.

The refined extract contains Cinerins 1, Cinerins 2, Jasmolin 1, Jasmolin 2, Pyrethrins 1 and Pyrethrins 2 as the insecticidally active component

Because the two pyrethrins isomers are the bits that do the work, only the pyrethrins content or strength is listed on labels as the active constituents. The piperonyl butoxide, (PBO) also listed as an active constituent, is a synergist that reduces the amount of pyrethrins needed to get an insect kill — same effect for much less cost.