 Hi friends, in the last class we discussed the status of pesticides across the globe and the history of the pesticides, how they developed and lastly we discussed the different classification of pesticides and then ended with the new class of insecticides classification. We will continue our discussion with regard to chemical control in IPM. Today we will understand how these pesticides act on insects that is the mode of action of these insecticides, nervous system of the insect and on the nervous system it used to act on four target sites, one the organochlorins mainly acting on the gamma aminobitric acid gated chloride channel, another group of insecticides organophosphates and carbamates, they are mainly inhibiting the acetylcholin esterase enzyme which in turn was controlling the production of acetylcholine chemical which is mainly responsible for transferring the impulses or the messages from one synopside to another synopsis in the insect nervous system. When the acetylcholine esterase enzyme was stopped automatically the insect could not transfer the message to the next cell thereby paralysis and death of the insect took place. Then the third one is formadine group of insecticides, they are mainly acting on the octopamine receptor of the nervous system again bringing in paralysis and death of the insect. The fourth target site is from pyrethroids this group of insecticides were acting mainly on voltage gated sodium channel, they were blocking this particular channel because of this also impulse could not be transferred to the brain hence which led to paralysis and death of the insect. After 1992 as I said in the last class lot of new class of insecticides were synthesized. If you see this diagram wherein I have clearly indicated the five modes of action of this new class of pesticides, the first and the foremost is insecticides acting on the critical synthesis, they inhibit mainly the critical synthesis during that process chitin is one of the important compound which is very much required for the formation of cuticle further at the time of molting. So, these products they were inhibiting this chitin synthesis thereby resulting in death of the insect. In the second case the insecticides mainly interfering in molting and metamorphosis particularly during molting you know we need agdazone hormone during metamorphosis we need joenil hormone, joenil hormone maintains the joenility of the insect, molting hormone helps in digesting the old cuticle and formation of a new cuticle. When these two hormones are interfered by various antagonistic chemicals then automatically it the growth and development of the insects is affected. So, the insecticides affecting this belong to this category of the mode of action. Then the third group of insecticides they were mainly interfering the metabolic process within the insect. Various enzymes required for digestion of the ingested material were affected because of inhibition of various enzymes during the process of metabolic activity and this also led to the paralysis and death of the insect. And lastly the effect on nervous system in insect is very commonly seen. This nervous system is action is in two ways. One it some of the insecticides it stimulates the nervous system some of the insecticides they inhibit the nervous system. In case of stimulatory nervous system the astral coloene receptor is destroyed and also the astral coloene receptor modulators are affected and then the voltage dependent sodium channel is blocked. Because of these three things the nervous system is stimulated thereby the over action of the insect takes place which again leads to improper impulse transmission from one neuron to the next neuron resulting in again paralysis and death of the insect. In case of inhibitory nervous system the gamma-minobiotic acid production is stopped. This again results in improper transmission of the impulse resulting in paralysis and death of the insect. This is how the new chemicals with four different mode of action we see the death of the insect ultimately. We now we have to understand what is the novel advantages of these novel insecticides over conventional insecticides. I have listed very clearly here all these new molecules or the novel insecticides have a better efficacy or the good by efficacy. Their mortality factor is very high and all these novel insecticides have high selectivity and less toxic to non-target organisms particularly parasotoids and predators and all these novel insecticides have very low mammalian toxicity and they have potent act by preventing the immature stages of the insect molting. That means they also interfere in the various developmental stages of the insect they affect the molting process of the insect and they are all used at very low concentrations. Just to quote an example you know chlorophyrophous insecticide is required to cover one acre of cotton almost 2000 ml. Now with these novel insecticides or new insecticides flubendomide for example we need hardly 20 ml to cover the same one acre of area with higher bio efficacy. So that is why I said they need at a low concentration. They are more target specific chemicals and replacing all the broad spectrum synthetic pesticides. All these new molecules very specifically they affect a particular insect rather than the broad spectrum insecticides and they are environmentally and ecologically very sound. Majority are green labelled insecticides because they are either derived or synthesized from plant origin or from microbes which are inhibiting in water. Then there is no question of resistance development unlike the old insecticides because they have different mode of action. If you see if you just see the last slide wherein there were five different modes of action. So each new novel insecticide is acting differently in by different means of action. That is why the question of resistance development is very very slow and then their residue in the soil is very minimum because of quick disintegration in the soil.