I live in Ft. Lauderdale and treat all my orchids monthly with orthene. Seems to work but I've heard that orchids can become tolerant... true?

[skirincich]

As an organic chemist with experience in the field of drug discovery, I am inclined to avoid pesticides which target biochemical systems that exist both in insects and humans. In the case of organophosphates, this class of insecticides binds to and inhibits the enzyme acetylcholinesterase (AChE) in nervous system tissues. Humans and insects are clearly very different yet share some similar cellular systems, including (AChE). If exposed to organophosphates, I am probably safer than insects due to my size. Clearly a 190 pound human can withstand a dose that is lethal to an insect. Here is where the risk assessment becomes a personal decision. Although more expensive, I prefer to use insecticides whose modes of action target biochemical systems unique to insects. The IRAC (Insecticide Resistance Action Committee) has some good information on the various modes of insecticide activity.