What is the History of PBO?

Mosquito The development of PBO grew out of a need in the late 1930s and early 1940s to enhance the performance of the naturally derived insecticide pyrethrum, which was considered an important insecticide against mosquitoes and other disease-carrying vectors, thereby providing public health benefits, e.g. preventing malaria. PBO was one of a series of molecules synthesized that had little intrinsic insecticidal activity of their own; however, they did increase the effectiveness of a given dose of pyrethrins
and were thus called synergists. PBO was first patented in
1947 in the US by Herman Wachs (Glynne Jones, 1998).