Neem Oil...I am in love with neem oil. It is rich in scent, great to use for pests on plants, and bugs in general do not like it! For this recipe 1 t will do.
I also suggest that you add a bit of homemade or organic (non-GMO, sustainably-sourced) vanilla extract. It has been an amazing addition to our spray at home. Those crazy little flies (that seem to have been running rampant this year) can't stand it. Again, for this recipe 1 t will work.