QUESTION:

You mix an IGR with a contact residual product, and for that matter say you also use something like Exiter to get a quick knock down when doing a clean out for, let's say, German cockroaches. So you have three products mixed in your B&G. If the cockroaches come into contact with the finished product how can the IGR be effective if the other products are killing the cockroaches within minutes. I know the IGR's work, I just don't understand in this situation how the insects can live long enough for it to work. Can the female pass the IGR to the embryo and if so woudn't the other products pass as well ect...

ANSWER:

This may be a little hypothetical on my part, but let's see where it goes. First, IGR's tend to last MUCH longer than contact insecticides do. Where you may get a few weeks of effective residual from contact insecticides you could expect many months of effectiveness from the IGR. So, even when the "residual" contact active ingredient is no longer doing anything the IGR continues to be present and affecting the roaches. The Exciter or any other pyrethrum is there for a rapid knockdown or for flushing only, and it probably disappears within a day.

Another factor is the nature of a couple of the IGR's, specifically methoprene (Precor) and hydroprene (Gentrol) whereby the active ingredient has some odd ability to move over the surface. This is why you can place a Gentrol Point Source under a counter and have it treat that wide radius around that point. The vapors of the hydroprene flow over the surface to redeposit, and thus can get into hidden places where you may not have actually applied the material. We might also consider the possibility that the roaches are sitting on too little of the contact insecticide to kill them, and the addition of the IGR adds one more tool to throw at them. We might use the same logic when we apply baits as well as sprays. By not relying on a single technique or product we increase the odds that what we expose the roaches to will ultimately kill them. These are tough adversaries, which is why we still are fighting them despite 100 years or more of trying, and despite the great many kinds of products available to us. Good German roach control could also involve vacuums, steamers, dusts inside wall voids, granular baits, etc.

The effect of the IGR on the roaches is to sterilize them, but I know with fleas it also can affect the eggs so that they do not develop properly. So, it may very well manage to get into the eggs and embyroes of roachs and work in that way too. This may occur more via contact with the eggs themselves, but perhaps could be from passing into the developing eggs from the mother. This may be more likely to happen with the active ingredients in some bait products where the a. i. is within the female's system. But, young roach nymphs that are exposed to the IGR do not develop properly. They still become adult cockroaches but now are physically deformed and hopefully unable to breed. The IGR does not kill the roach,  but prevents it from creating more roaches and thus depletes the population.

Bottom line is that we might be too optimistic thinking that we are going to be able to kill all the roaches within minutes using just the contact insecticides alone. They are much too stealthy and evolved for this to happen or we would have wiped them out long ago. Because of issues like repellency, resistance, breeding potential, and their varied hiding places we need to throw the entire line of choices at them when possible, and putting it all together we kill more roaches than any one product could do on its own.

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