Dr. Michael Scharf of Purdue University presents a comprehensive overview of insecticide classification and mode of action for pest management professionals. Scharf covers insect physiology fundamentals, the key-and-lock relationship between insecticides and target sites, and nine insecticide classifications — five neurotoxic and four non-neurotoxic. The presentation concludes with practical factors affecting performance including formulations, pest behavior, sanitation, and resistance management. Q&A moderated by Dr. Dan Suiter.
45:18 Inhibitors of Energy Production — Hydramethylnon, Chlorfenapyr, Fumigants
46:56 Cuticle Dehydrating Dusts — Silica Gel and Diatomaceous Earth
48:15 Factors Affecting Insecticide Efficacy
48:46 Stability, Persistence, and Formulations
51:02 Pest Behavior — Secondary and Tertiary Kill, Trophallaxis
53:04 Sanitation and IPM
54:19 Resistance Management — Rotation Strategies
56:30 Summary Points
57:44 Additional Resources
57:53 Q&A — Combination Product Resistance
59:53 Q&A — Flow of New Active Ingredients to Market
1:01:08 Q&A — Chlorantraniliprole and Non-Target Invertebrates
1:01:40 Q&A — IRAC Classification System
1:02:38 Q&A — Nicotinoids vs. Neonicotinoids
1:03:43 Q&A — Oral vs. Dermal Toxicity Routes
1:04:43 Q&A — Repellent vs. Non-Repellent Insecticides
1:05:32 Q&A — Essential Oils and 25B Exempt Products
FREQUENTLY ASKED QUESTIONS
Q: What are the four basic insecticide modes of action?
A: All insecticides disrupt target sites through stimulation, blockage, modulation, or inhibition. Understanding these four mechanisms provides a framework for classifying any product a professional might encounter.
Q: Why are diamide insecticides considered especially safe for mammals?
A: Diamides target insect-specific muscular calcium channels. Their mammalian toxicity is so low that the EPA initially required no signal word, though manufacturers voluntarily adopted a "caution" label.
Q: Why is resistance a major concern in cockroach management?
A: Research has documented cockroaches surviving on bait as their sole food source for a month. Even combination products face dual resistance. Rotate active ingredients every three months or monthly.
Q: How does the IRAC help pest management professionals?
A: The Insecticide Resistance Action Committee classifies active ingredients by mode of action, helping professionals plan rotations between different target site groups rather than simply switching trade names.
Q: What is the difference between repellent and non-repellent insecticides?
A: The distinction largely comes down to pyrethroids versus everything else. Pyrethroids are highly detectable to insects — like "pepper spray" — while most other actives are not nearly as detectable.
RESOURCES
• Scharf & Suiter, "Insecticide Primer and Insecticide Mode of Action," PCT Magazine, 2011
• Scharf & Suiter, "Insecticide Basics for the Pest Management Professional," UGA publication
• IRAC Mode of Action Classification Chart: https://irac-online.org
