How Do IGRs Affect Cockroaches?

I recently had a message come in from someone who wants to better understand how IGR’s affect cockroaches, especially the brown banded cockroach, Supella longipalpa. (By the way, the picture currently on Wikipedia for the brown banded cockroach isn’t the best.)

Ah, not only are cockroaches one of my favorite pests, but brown banded cockroaches in particular hold a special place in my heart. I still remember the first time I saw them, back in 1999 in a Riverside, California home. I opened up the kitchen cabinets, specifically under the sink, to inspect for pests. Crouched down, I peered up inside the cabinet, shining my trusty rechargeable Maglite into the dark recesses where the sink was attached to the cabinets. And I saw, for the first time ever, small egg cases glued onto the cabinetry. Small glued egg cases in areas such as this are often a sign of brown banded cockroaches. Unfortunately, there were no live cockroaches.

Perhaps brown bandeds would be a good entry for a future blog… in the meantime, let’s get down to the mail!

Dear Mr Snyder: RE: german cockroaches -esp those prodigious quantities that I endured during a quarter century in New York City Rental Apts ( my first landlord was Trump assoc) What exactly are Insect Growth Regulators ( “juvenoids)- are these effective in controling just the German cockroaches or can these IGR be used for Brown Banded critters??? Do these require like 6 months to get rid of roaches??

Would I be correct in assuming that you are familiar with Andre the Giant and, more than his wrestling and acting career (“anybody want a peanut?”), his health problems?

Andre was unhealthy and died young because he had an excessive amount of growth hormone. He couldn’t stop growing.

IGR’s work similarly on insects. Young cockroaches, once exposed to an IGR, will not grow up, but rather will stay immature and keep on growing, like Andre. And, like Andre, although they won’t die immediately, their lifespan will be shortened. Since they never grow up, they cannot have children.

Through this affect, IGR’s stop the rapid growth of cockroach populations.

Adults are affected differently.

There’s no affect on adult males.

Adult females increase their feeding. So, if you are using IGR’s along with cockroach baits, the bait becomes more effective.

In German cockroaches (but not brown banded), females will carry their eggs until hatch. An IGR will cause them to abort their egg cases, causing the eggs to die.

I don’t recommend using an IGR alone. Although in theory you should be able to get control with only an IGR, it would take a long time (you quoted 6 months – I’m not sure if anyone has done a study to find the exact length of time), they are best used along with baits, sprays, or other treatments.

They will be very effective on all types of cockroaches.