What's the best technique to kill German roaches. I've tried with Advion, Intruder, and wettable powders. They seem to come back.
The German Roach isn't the most successful pest roach in the world by accident. It is a survivor, and likely will be around to laugh at us when humans disappear from the planet. They can be very adaptable in a structure, but not invincible. I think we really can accept that pesticide resistance is not a major factor at this time, even though it does exist in some roach populations for some kinds of insecticides. However, for the majority of our commonly used products, if you put the roach and the active ingredient together for a proper length of time..... the roach is toast. If the proper concentration of a.i. is present on a surface, and the roach sits on that surface for a few hours, it certainly should absorb enough of that a.i. to cause its death, and the products you mention would be as effective as any.
When you have this lingering cockroach problem I think that one of two things is happening. Either you are getting a consistent RE-invasion of new roaches to the accounts, or the more likely scenario where the roaches you continue to find are simply hiding someplace where you are not treating. We know, of course, that you can eliminate 100% of the cockroaches in a restaurant, and have new ones imported the next day in infested packages, which is the usual means by which German roaches get from place to place. This is the reason a commercial account, like a food service account, should keep a pest management service full time. The pressure on their facility by roaches is constant, and while you may not (and should not) spend all of every visit "spraying" something, there definitely ought to be constant monitoring and inspecting to find that new infestation when it occurs.
German roaches prefer to hide as close to their food as possible, but they also are willing to walk long distances if necessary. We may tend to treat an infested account rather robotically, focusing on all the usual places where these roaches are so common. But, depending on the kind of account, they could be in any room, inside the walls, inside equipment, inside closets, etc. A lot of the pesticides we've used for them also have some repellent properties, and the self-respecting roach may detect this and move to some harborage that has not been treated. When all the things you've been doing seem not to be working I like to suggest leaving the sprayer in the vehicle, and making the next visit to the account with a flashlight and clipboard, and maybe knee pads, because you should spend a lot of time down on the floor inspecting for every possible missed harborage point.
The clipboard carries your written Sanitation Inspection Report (or whatever you'd like to call it) on which you document everything you find that is encouraging these pest insects to be in this place. The roach cannot survive in a structure unless it finds The Big Three - food, water, and harborage. Take away all of any one of those and the roaches cannot live there, so these are the things you are looking for when you inspect. Now, this is going to require the cooperation of the customer, which may be difficult to get. But, unless they are willing to clean up food opportunities, dry up water resources, and close off access to harborage they are telling you that they want a complete reliance on pesticides to take care of the problem, and this is not what we are all about. The recent focus on "green" pest management is a very good one, because it causes the public also to understand that over using pesticides while ignoring the contributing factors is not the proper approach.
There is nothing at all wrong with the products you already have used, but in all likelihood you have not found a few harborage points. The use of roach baits is excellent, and make sure they are applied as small spots directly into crevices and small voids - this is where the German roach prefers to feed. Apply residual products directly into crevices and voids as well, avoiding those where you plan to place the baits. Consider treating wall voids around the area where the roaches are being seen, using a residual dust or fogging with a deep void injector like the Patriot or Actisol. Use an IGR like Gentrol or Nylar, along with your application of the residual product or with Gentrol Point Source tabs, and this gives you one more weapon that does help to break down the roach population. Use liberal numbers of insect glue traps to help determine where the roaches are coming from, and this can lead you to some of those harborage sites you may be overlooking.
Mr. Pest Control
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Please note, Mr. Pest Control is answering questions supplied by PMP customers across North America. His answers are generated from industry and manufacturer-provided information. The answer may not be specific to the laws and regulations for your State, Province, Territory or Country. In addition, products mentioned may not be registered and or available in all areas. Always check with your local Univar office for specific information to your area. Always read and follow label directions.