Thursday, April 21, 2011

Differences between Immunity, Resistance and Bait Averse

What is immunology? I often hear people saying this insect immune to this Pesticide A and Pesticide B but, are they using the correct term?

Immunity is the body's ability in fighting for the large range of pathogenic and parasitic organisms. Immune system involves a series of steps which called immune response. The immune system will attacks organisms and substance which invade into the insect's body and cause disease to them. This is nothing related with chemicals as it concerns on pathogens infection and its immunity in fighting the disease. Compare with mammals, insects have shorter life time (mostly few months of few years) and with the simplicity of nervous system, they do not have immune memory.

The above photo is a good illustration on how does resistance form in the insects. In this diagram, it shows the first generation weevils have weak resistance to pesticide and high resistance to pesticide. Red weevil represents high resistance and after the pesticide application, you may see the red weevil still surviving and 2 more white weevils as survivors. When these first generation weevils reproduced for the second generation, the second generation will have a stronger resistance to pesticide compare with the earlier one. And when we treat the weevils with the same group of chemicals as the first round, they are more weevils can survive compare with the first generation. This shows that the resistance have formed and the same story will apply to the following generations. Therefore, it is advisable to rotate the chemicals. Continous spray with the same group of chemical will eventually help the insects on creating resistancy to the chemicals. This will lead the insect's control method fail in the end. When you rotate chemicals, please look into mode of action of the chemicals. Do not rotate back the same group of chemicals which give you the same mode of action. By doing this, you are actually not doing the proper chemical rotation.  

(The above photo does not belong to Carron Lee. It is an extract from internet)

Bait averse is a behaviour of rejection to the bait. Bait is a combination of attractants and active ingredients. Aversion happens when there is a large amount usage of the similar bait at the same infested area. When there is overdosed of baiting treatment, it will actually form bait averse behaviour and you will claim that, your pest control service provider is failed in achieving the acceptance tolerance level of your cockroaches infestation. Therefore, you need to rotate the gel. Regardless, how often you rotate it, is depend how you study your infestation area. Do not over treated the area. By blindly increasing frequency of treatments without any study on the infestation is not a wise choice. Cockroaches actually averse to the attractant of the bait and not the active ingredient of the bait. Can you imagine, how's your appetite will be if every day, you eat nothing but McDonald? How 'bout McD's meals for 3 months? Will you still eat McD if you are forced to continue? This is what exactly is happening to insect bait averse behaviour. In order to have a good pest management system, we shall have combination of various methods, understand the infestation area and apply when necessary. Put yourself in insect's shoe and you will get a better way to control it.


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