 Hi friends, in the last class we understood what are the considerations to be given while selecting a chemical or a pesticide to be included in pest management. Fine, to continue that discussion on chemical control in IPM, one of the next important aspect is the insecticide resistance development and its management. Why the insects develop resistance? So that is one of the important question to be answered. In simple I have indicated here, the insecticide resistance is the development of an ability to tolerate doses of an insecticide, which would prove lethal to the majority of the individuals of the normal population of the same species or in general, when you repeatedly apply a particular pesticide, then automatically the same species will develop some short of tolerance to overcome this particular dosage and cause economic damage, which can be very clearly explained with this slide photograph. You see here both the susceptible ones and the resistant ones, the susceptible ones and the resistant ones in this agro ecosystem. When you spray a particular insecticide to this ecosystem, the susceptible one keeps on eliminating only the resistant ones, which remain. So when this population goes on increasing in the given ecosystem, even after spraying, you notice in the decrease in the population, thereby the economic damage also increases. When you see the economic damage, even after spraying, then you feel the insect has developed resistance. So this is a simple concept. If you trace the history of the insecticide resistance in insects, it goes as back as in 1914 itself. People thought, many of the people thought with the discovery of Miracle powder DDT, everybody thought that the problem of pest is solved once forever. They also thought they have won the war against insects, but that statement did not remain for a long time. You know the scientist got the first jolt during 1946 itself, when housefly showed resistance to this Miracle powder DDT itself. So leave aside that, even as back is in 1914 before the synthesis of the synthetic insecticides or before understanding the insecticidal property of DDT in 1939, Melander in 1914 guessed that Sanjos coal, Sanjos scale insect has developed resistance to lime sulphur. He wrote an article, in fact, can insects become resistant to sprays, which at that time nobody gave an importance. But later on during 1941, the Colorado potato beetle developed resistance and then one of the medical pest that is particulars during 1944 showing resistance to DDT. Then after 1946 particularly, series of insects showing resistance to various groups of insecticides started pouring in from different parts of the globe. The first resistance report internationally, we see in case of as I said lime sulphur on Sanjos scale and within the country, the first national report of resistance came from Singhara beetle particularly on DDT and BHC from Delhi, which was reported by Pradhan et al. And then I have here a list of resistant insects abroad. So starting with Sanjos coal, tobacco, but worm showing resistance to pyrethroids. Then DBM diamond back moth showing resistance to chlorentryprinol from China. Then lady beetle showing resistance to lambda silo-trin from Brazil. Again diamond back moth from China. So like that the number of insects went on increasing, showing resistance. Similarly in India, the resistant report was started from as I said earlier, Singhara beetle from again as to DDT from Delhi area. Then in case of paddy ecosystem, rice leaf folder showing resistance to two OP compounds, chlorophyry fuzz and quinol fuzz. And then cotton bowl worm, helicover parmigera showing resistance to both OP compounds. And then spotted bowl worm showing resistance to carbamide again in the cotton ecosystem. So like that the list went on increasing day after day. The ARAC insecticide resistance action committee, they have compiled the 14 top countries where the number of cases of insecticide resistance have been reported. If you see this particular graph, USA dominates with the 2400 species of insects reported having resistance to various groups of insecticides followed by Pakistan. And we are fifth in the ranking having around 450 species showing resistance to insecticides. Then in terms of groups of insects also they have categorized diptera recorded maximum number of species having shown the resistance to insecticide followed by lepidoptera and homoptera. You need to understand why the resistance develops in insects. That is the reasons for developing resistance. I have listed some of the important reasons here. First and the foremost is continued and frequent use of pesticide. That is overexposing a particular pesticide molecule for a pest. So applying the principle of selection pressure, the insects started developing resistance. Then use of application rates below or above than the recommended ones. Particularly the lower recommendation has its own impact on resistance development, simultaneously higher dosage also has a major selection pressure for a particular insecticide. Then whenever they spray poor coverage of the particular pesticide in that treated area, thereby there will be always possibility of the survival of the insect species wherever the treatment or wherever the spray is not covered. Then frequent treatment for insects having large population and have got shorter life cycle. One of the classic example is cotton white fly. White fly can complete its life cycle in 14 days and more number of generations can take place. To manage white fly people started applying repeatedly almost once in three days they started applying which resulted in higher selection pressure and leading to higher level of the insecticide resistance. Then failure to incorporate non-pesticidal control practices in a given ecosystem whenever you see the insecticide resistance people forget the other methods of pest control. They only think of insecticides which is another major problem why the continuous development of insecticide resistance took place. Then simultaneous treatment of larval and adult stages with single or related compounds. Say in a given ecosystem for example in red gram if you go on applying the OP compounds belonging say for example monocrotophos, chlorophyryphos, quinolphos they all belong to OP compounds and their mode of action is also same. So if you repeatedly alternate the insecticides belonging to the same group in this case OP compounds naturally the selection pressure for the particular compound increases thereby the resistance development is much faster. Similarly the insect is also a living organism you know genetic mutation and inheritance takes place because of the continuous exposure there is a genetic imbalance in the insect. A physiological adaptations take place various mechanisms particularly biochemical mechanisms that the insects has developed to detoxify the toxic compounds of these insecticides. That's how these are all the major reasons why the insect develops resistance. Then more important in the chemical component of pest management how to overcome this resistance which has been developed various simple strategies have been recommended. First and foremost is use of judicious and recommended dose of insecticides. Then most important is you know as I already said insecticides have different mode of action different target site of action different cross resistance considering all that knowledge we have to use insecticides having different target sites different mode of action. Then as I said insecticides belong to different chemistry alternate use of chemicals which have different mode of actions will certainly slow down the process of selection of a resistance to a particular compound. Then use of cultural practices which are the basic tactics in pest management which can be incorporated and then we can reduce the selection pressure for a particular insecticide. Then one should understand the life cycle of the insect when exactly the egg stage is there when exactly the larval stage is there the early stages are more vulnerable for pesticide application. Looking to this you need to target your application coinciding with the early stage of the insect. Use of insecticide mixture is one of the immediate answer for our farmers. You know when one product is not working certainly combination with another product for example the synthetic pyrethroid in combination with the organophosphorous has a synergistic effect on the mortality of a helicoverpine cotton ecosystem. So insecticide mixtures also is one of the answer in IRM strategy. Then we need to use some of the synergies in the form of simple oils, sesame oil and then sunflower oil are some specific pure piperinole butoxide. This is one of the important detox because all these oils and PBO they detoxify the enzymes which are responsible for resistance. So such oils and the piperinole butoxide you know addition can overcome one of the important problem of insecticide resistance management. And lastly we need to conserve the beneficial fauna for example in a given ecosystem like paddy spiders play a major role considering the spider fauna if there is one spider per plant that can do over almost 15 to 20 BPH adults in a given day. So when this is there why to go for pesticide application? If you avoid pesticide application itself the insects which have developed the fauna the BPH which has developed a resistance to some of the insecticides will be taken care by these predators. This is how the resistance can be managed in case of insects. Thank you.