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Avoidance and Resistance

Pest Control Problems with Sprays and Baits

Of the many ways that pest management programs can possibly fail, insecticide resistance and bait avoidance are two topics that are not always understood and even recognized in do-it-yourself pest control as well by professional pest control service technicians.  This article will address bait avoidance, insecticide resistance and other topics that sometimes cloud the issue: the flushing action of insecticides, the ability of pesticide sprays to contaminate insect baits and how crack and crevice tools are used to flush out targeted pests into the open.

Bait Avoidance, Immunity to Pesticides or Pesticide Resistance

Pesticide Resistance    Flushing Action of Pesticides    Bait Avoidance    

Bait Contamination         Bait Index    Roach Baits    Ant Baits 

Pest control operators, their technicians as well as the general public are all concerned with chemical, pesticide insecticide resistance and other somewhat related problems with different pest management tools. To confuse the picture (more than it already is!) is another concern: bait avoidance.
If you do your own pest control you might encounter a problem of targeted pests avoiding an insect bait, whether it be for ants, roaches, crickets or silverfish.   These instances are not as common as you might think but when they do happen you need to know how to handle the problem. As will be explained in this article, there is such a thing as resistance to an insecticide (active ingredient in sprays and baits) and there is also a phenomenon known as "bait avoidance." 

There is a difference between bait avoidance and bait contamination.  Avoidance occurs when selected pest populations actually avoid parts of the bait being applied.  Contamination occurs when an outside source causes the bait to become unacceptable to the targeted pest. 

Bait Contamination        Bait Avoidance

Any bait can be contaminated: roach, carpenter ant, fireant, silverfish and regular ant baits in gel, solid, liquid and granular formulations as well as rat and mouse baits (rodenticides) in solid block, bulk pellet and place pack forms.

Baits usually fail when the baits are exposed to tobacco, pesticide sprays, mop water, cleaners and other materials that make the bait work completely opposite of its intended use - bugs are repelled instead of attracted.
[In a few, isolated cases German cockroaches have been known to avoid a roach bait that was not contaminated by any outside source.  In this case there is a true bait avoidance.]
Keep it simple: baits should attract, not repel.  Repeated cases have proven that using a bait and a spray in the same room results in a few bugs dying from the spray and the bait placements fail.  When the correct bait for each particular job is placed in the proper areas and no sprays are allowed in the same area, the bait will do its job.  This is even more evident with baits such as Maxforce FC Roach Bait Gel, Maxforce Ant Killer Gel or Maxforce Carpenter Ant Bait are used.  These particular baits have an active ingredient (Fipronil) that has a domino effect on the targeted ants, fireants, carpenter ants and roaches.  
Do not kill the messenger!  If a roach that touches or feeds on your roach bait will in turn kill dozens of other roaches by transferring the bait material, why would you want to kill that roach (with a spray or dust) before it has a chance to come into contact with other roaches in the population?  
Do not take a great tasting food and change it into a disgusting food!  Would you eat your favorite meal if someone covered the food with a foul smelling liquid?  Do not ruin your bait by letting it come into contact with bug sprays, foggers, bug bombs or insecticide dusts.

There are service technicians that have not been properly informed on this subject while others fall prey to yielding to their customer's demands in situations where the customer needs to be educated about proper pest management procedures.  A common example of this when a customer demands that their roach infested home be fogged when the technician knows that fogging the structure might at first look impressive to the customer, it (fogging) is not always the best way to exterminate the roaches.
There are two basic ways to ruin your good roach or ant bait: contaminating the bait with pesticides and trying to get a leg up on the situation by fogging and/ or spraying prior to baiting the structure.  This last method usually defeats the special domino effect of advanced formulas of ant baits and roach baits.
If you go to the trouble of properly baiting the structure with a good professional bait, you should then leave the baited area alone!  Coming back (after baiting) with a contact spray or fog will contaminate the bait.  Would you like to eat a desirable food that has been doused with an insecticide?  Of course not - and neither do the roaches and ants in you home.
We have had customers that were instructed on the correct use of roach and ant baits but their pest control project fails because of their impatience.  They cannot resist the temptation of setting off a few bug bombs in their home before applying their professional bait.  
Top of Page

Synthetic classes of insecticides have a flushing action that is not to be confused 
with avoidance.
The Pest Control Terms
Insecticide Resistance/ Immunity     Bait Avoidance     Flushing Action

Insecticide Resistance, Pesticide Immunity
Since there are far too many pests to discuss in this article, we will concentrate 
on cockroaches. The cockroach as an amazing creature that would be fascinating 
to everyone if there were not such a pest. Their ability to adapt is what makes 
them such a pest that they will probably never be put on the endangered species 
Let us say that there are 1,000 cockroaches in your kitchen and you decide to use 
a spray to exterminate the roach population. Let us also say that you spray the 
area with a solution that contains Cypermethrin. Thirty days after spraying the 
kitchen, there are about two hundred roaches still alive. Most of these surviving 
insects are probably hiding in wall voids or other areas that your spray could not 
possibly reach. Only if the roaches leave their hiding places and crawl across the 
treated areas will they come into contact with the insecticide.
Of the 200 cockroaches that are remaining, there could be five of the insects that 
were in fact exposed to a lethal dose of the bug spray but were not killed by the 
bug spray. These five are said to be "resistant" to that spray. In other words they 
are considered to be "immune" to the effects of the insecticide.
Why are the roaches not killed by the spray? The remaining roaches in our 
example of a treated kitchen are still alive after being exposed to one of the best 
roach sprays on the market. These lucky bugs have an enzyme that breaks up the 
pesticide molecule which is then flushed out of the insect's system, in much the 
same method that our own bodies have the ability to catch foreign or dangerous 
particles and then send them on their way through our very own waste 
management system.
The lucky roach in question was born with this particular enzyme and will pass it 
own to its offspring. In other words, the roaches exposed to a certain pesticide 
spray do not necessarily "build up" a resistance to the spray but instead are given 
the lucky pass handed down to them by their ancestors.  In the chain reaction that follows, 
more and more of the resistant strain are seen as the roaches multiply.
How do we take care of a population of resistant roaches? That problem will be 
discussed in the resistant roach control section.

chemical resistance

Over the years we have seen many new products introduced to the pest control 
industry but it is not often that we see new classes of chemicals. Most resistance 
is seen in classes of products. For example, pest control service technicians in 
the 70's and 80's relied on organophosphates for most general purpose pest 
control. In this particular class of chemicals are a couple of products that are 
familiar to the general public: Dursban and Diazinon. Another class of products 
was also used in the 70's: the Carbamate. Two Carbamate products that were 
very popular were Baygon and Ficam. When a pest control operator saw that he 
was not getting the desired control using Dursban, he would naturally switch to 
another chemical for at least one month. Very little change was noticed if (for 
example) the pest control operator (PCO) switched from Dursban to Diazinon. A 
greater change was noticed when the PCO switched from Dursban to Ficam or 
Baygon. The reason for the difference was not in the products so much as in 
which classes of chemicals the products belong.

If a population of German Cockroaches becomes resistant to a chemical, that 
population is usually resistant to almost every chemical in that particular class.

Bait Avoidance         Bait Contamination

Roaches and ants will sometimes refuse to eat a specific bait because they are repelled by either the bait's attractants or the active ingredients used in the bait formulation.  The rejection of a particular bait that has not been contaminated is called bait avoidance.

When people use insect baits for controlling ants or roaches in their home but do not get the results that were expected, they usually blame the product that they purchased and used - or the person that suggested the product.  As seen in the bait contamination section, even a good professional bait can fail if it is not used properly.  (There are also other reasons for bait failure: choice of bait, proper identification of targeted pest, bait placement, etc.)
In most cases of reported bait failure, the problem lies in bait contamination.  However, it is possible for the targeted pest to be repelled from the bait (instead of attracted to the bait) when everything from selection of product to application of product has been done as directed.
Several years ago it was documented that in a small, isolated area of south Florida, there were roaches that actually ran away from or avoided the best cockroach bait on the market - Maxforce Gel Roach Bait.  The manufacturer of the product immediately researched the problem and found that there was one single item in the bait that these peculiar roaches were avoiding: a particular type of sugar.
Once this material was replaced with another attractant, the problem was solved.
Maxforce Roach Bait remains as the favorite of most pest control operators and has become very popular with the public.  Another excellent bait for getting rid of roaches is Invict Roach Bait Gel.  Invict Cockroach Bait is showing excellent acceptance and also kills roaches faster than other baits tested.  You can now purchase Invict Gold in different sizes: Invict Gold Single and Invict Gold Box.
Rotating between Invict Gold Cockroach Bait and Maxforce Magnum is a great idea.  Both baits are excellent.
On rare occasions you might hear of roaches or ants refusing to feed on an excellent bait.  When this happens, switching to a different bait usually solves the problem, especially if an effort has been made to eliminate other food sources that the targeted pest would naturally feed on.
In libraries, on the web and other places you can often find home-made recipes for roach or ant baits.  Some of them have only one or two attractants that may or may not get the interest of your targeted pests.  Along with attractants there must be something to kill the roaches, an active ingredient.  In some cases the active ingredient itself can repel roaches.  There is a delicate balance between attractant and active ingredient in any bait.  Professional baits now contain several different attractants to make them attractive to roaches, ants or crickets of different species.  This is important because pest populations in various locations can often have a different diet from others of the same species in other locales.
The active ingredients in modern, professional baits have been chosen for effectiveness, safety for the end user and lack of repellency action to the targeted pest.

Flushing Action

Flushing Out Pests with Crack and Crevice Work

Flushing Action of Certain Pesticide Sprays

After spraying a home or business for cockroach infestations, many customers 
will complain that "all the pest control company did was feed my roaches!" This 
reaction is usually due to the flushing action of either the residual insecticide 
spray, the crack and crevice tool used after spraying or a combination of the two.  The only other time this "feed my roaches" complaint is heard is when the pest control technician has a real problem getting the roach problem under control.
Residual insecticides that are sprayed in cabinets, on baseboards and other 
common indoor spots are usually in a type of product called "contact 
insecticides." As their name implies, the targeted bug, spider, insect must come 
into contact with the applied chemical in order for the chemical to do its job. 
With most of the pest population hiding in wall voids and other out of the way 
places where contact insecticide sprays cannot always be used, good pest control 
technicians rely on the use of crack and crevice tools to finish the job. After 
spraying inside a home, using their professional sprayers that contain a safe 
solution of a contact insecticide, the technician then begins the hard part of the 
job - which is also the most important part of the job: crack and crevice work.
Armed with either a hand bellows duster or aerosol that has an attached straw or 
tube, the pest control professional attacks the tiny places where most sprays 
cannot be used. Any small area where bugs can slip through is treated with the 
crack and crevice tool. If a pencil point, playing card or business card can be 
inserted into an opening, a bug can and probably will use the opening as it travels 
through your home.

Pesticide Flushing Action

We are now in the post-organophosphate/ chlorinated hydrocarbon era. With 
organophosphates such as Dursban, Diazinon and Dursban Pro no longer being 
produced for indoor residential pest control, synthetic pyrethroids are the 
mainstay of pest control sprays. While some may lament the demise of bug 
sprays made from Dursban and Diazinon, the pest control industry is better off 
with the more modern products left for pest control operators and the public to 
As the remaining supplies of the last few Carbamate and organophosphates are 
used up, the vast majority of general purpose pest control (as well as turf and 
ornamental pest management) is being done with synthetic pyrethrins. These 
man-made pyrethrins are commonly known as "pyrethroids" in pest management 
industries. Pyrethroid insecticides, as a class of insecticides, offer us a better 
product with far less possible hazards than older classes of insecticides. There 
are many ways in which synthetic pyrethroids are better than older classes of 
insecticides but for the purpose of this discussion the flushing action will be the 
center of attention.
Man learned long ago that powder made from specific plant blossoms had some 
unique properties: low toxicity, low possible hazards to humans, pets, domestic animals, quick knock down of insect pests and no residual action.
This pest control material has been slightly modified and is widely used for killing many different invertebrate pests in a wide variety of areas 
needing control. The material is what we now call natural pyrethrins. These 
pyrethrins can be used on animals, in homes and warehouses and in some 
outdoor applications. There is a trade-off with pyrethrins: although they are 
considered extremely safe to use in sensitive areas, when used properly, they 
have no residual action. A good example of this would be common flea and tick 
sprays for dogs and cats. The active ingredient (pyrethrins) has a very fast 
knockdown or quick kill for fleas on pets but an hour or two later there is no bug 
killing power left on the animal - pyrethrins are safe to use but are not very stable 
for long term pest control.
Another great property of pyrethrins is their ability to flush pests out of hiding 
places. Pyrethrin aerosols are often used for this very purpose. When a short 
blast of this aerosol is close to where roaches and other bugs are hiding, they 
usually leave their hiding place in a hurry.
Experts now know how to mimic natural pyrethrins by developing a very similar 
molecule - what we now call a synthetic pyrethrin or pyrethroid. With these so 
called "synthetics" we can now enjoy the best of both worlds: much lower hazard 
possibilities to people, pets and domestic animals but with the staying power or 
residual activity of older chemicals.
Synthetic pyrethroid insecticides also have the flushing property seen in natural 
pyrethrins. When Cypermethrin was first introduced to pest control operators, 
many of their technicians stopped using their crack and crevice tools. This 
happened because as technicians started spraying inside homes with Demon WP 
and Cynoff WP, the flushing action of the chemicals were so great that roaches 
would literally "rain down" out of cabinets and light fixtures that were far above 
the actual surfaces treated with the insecticide! Seeing this initial reaction to the 
insecticides containing Cypermethrin, many technicians simply stopped using 
their dusters and aerosols.
With pest control technicians now being trained in greater detail on integrated 
pest management (IPM), the use of hand bellows dusters and crack and crevice 
aerosols is beginning to rise back to proper levels.  Extensive crack and crevice work not only finds the hidden areas where bugs forage, travel, feed and breed but allows for a decrease in amount of chemicals used in a home.  

Crack and Crevice Flush Tools
Using Crack and Crevice Tools to Flush Hidden Bugs, Pests 

When an insecticide dust (Drione Dust, Delta Dust, Tempo Dust) is puffed or injected into these  voids where roaches and other bugs enter, hide, forage, breed and feed there are  two good things that happen. First, any roach or spider that is in the immediate  vicinity will many times be flushed or chased out of their hiding place. As they  leave these crevices they can be seen crawling across baseboards and other areas  where the residual contact insecticide has been sprayed. In other words, they run  from the frying pan into the fire!
The second aspect of dusting cracks and crevices is the very nature of a propelled 
dust. These dust particles travel through voids and hidden areas behind walls, 
traveling a much greater distance than liquid applications. Not only is the bug 
killer pushed deep into bug hiding places but the propelled dust has a tendency 
to cling to surfaces. If you simply place piles of insecticide dust in an area, most 
roaches and other bugs will crawl around the unattractive obstacle. But when you 
properly use a hand bellows duster or electric duster to apply your dust, the dust 
particles are charged and will stick to most of the surfaces they meet. Now your 
targeted roach, ant, spider, cricket or other pest cannot escape your insecticide 
application because it covers everything the bugs touch with a nice, thin layer of 
As you can see, flushing out pests is a good thing and can be accomplished 
through the use of synthetic pyrethrin insecticides and good crack and crevice 
work. This work can be done with either dust or aerosol. An aerosol that is 
equipped for cracks and crevices is handy and is often preferred. Dusting certain 
areas of a home or business is best because more areas can be treated, the 
material travels further in voids and insecticide dusts give you a much longer 
residual activity than do aerosols. 

Maxforce Baits    Maxforce Gel Roach Bait    Index of Baits    Cockroach Index    Ant Index

Pest Control Supplies    Pest Control Information    Index of Pests    Resistant Roaches   Bait Avoidance