Aavo from Sterling, Va writes
Insecticides using the ingredient Pyrethrin are normally contact kill only products due to the nature of the ingredient derived from the crysanthymum plant. The Harmonix Insecticide has other inert ingredients in it which give it both contact kill and residual properties. Each product containing pyrethrin will vary on how it is produced as to how it works. Please let us know if you have any other questions.
Answer last updated on: 07/19/2013