 Hi, welcome back in the last class we understood about some of the microbial pathogen employed in a pest management. In this class let us look at another important the microbial pathogen or the bio agent which we can use it for the pest management system and also look at some of the advantages and the limitations of the bio control program. Entomopathogenic nematodes or the EPNs are also comes under this group of causing the diseases in the insect. You know that there are many groups of nematodes which are also considered as the plant parasitic which causes the diseases in the plant. Similarly, there are certain groups in the nematodes which cause diseases in the insects and taking some of those groups. So there is a lot of commercial exploitation made in managing the various insect pests. Those what are the EPNs? If you define the EPNs they are those nematodes which are capable of killing or sterilizing or seriously hampering the development of the insect and completing at least one stage of the life cycle in the host. So there are several groups are there but I am just concentrating on three important groups. So one is the family under mermithidae which comes under the order inopleda and this has got a bio control potential against the dipterans and that has been developed. But we are looking at these two families. This family is tiner nematidae and the heterorabdytidae which comes under the order rabdytidae are globally well exploited for managing the pest. Why these two nematode groups? Because these have got a very tremendous potential of causing the host mortality very quickly within 24 to 48 hours. As you know that the bacteria, the fungi and the viruses will take around 4 to 7 days in killing the host whereas these nematodes as soon as they enter into the body they quickly they bring the mortality and also they have got a very wide host range so nearly more than 200 insect species of 10 orders of insects they are susceptible to the entomopathogenic nematode and they have got a wide distribution they are found in all parts of the world except the cold region and most important one is that they have gotten a symbiotic association with the bacteria that is Xenorabdytidae species in case of tiner nematidae and heterorabdytidae species in case of heterorabdytidae. In fact it is the bacteria which they carry are going to cause the death of the insect and these nematodes are simply the carriers of the bacteria and they have a third infective stage which we call it as the infective stage is juvenile which is a non-feeding, free living and durable and capable of withstanding the adverse climatic changes. This is a great advantage as this stage can freely live in the soil without food for several months and also withstand the adverse condition only when get a suitable host then it can enter and then actually kill the insect. Then another great advantage is it can be mass produced both under the natural host and as well as the artificial diet. It also has got a good shelf life and it is an easy to apply which can be used with very conventional sprayers we can apply it and it is safer to the non-target organism. In fact the entomopathogenic nematodes have been exempted from environmental protection act because of their safety to non-target organisms. Now let us look at the mode of action of this entomopathogenic nematode. As I was telling you earlier the infective stage or the third juvenile stage is the one which is free living and which will be always seeking the host. So once it actually seeks the host then it enters into the host body either through the natural openings such as the mouth part or the anal part or sometimes they also go through these pyricles which are the tiny openings for respiration. And once they enter into it then they penetrate into the hemosyl and then they release the bacteria the symbiotic bacteria is released by the nematode and this bacteria produces lot of toxins and these toxins are going to kill the host cells by septicemia. And once the host is dead then the nematode will start multiplying instead either they will complete the first or the second generation depending upon the size of the host and then they will continue to mass multiply and once the host food is over then the infective juniors are going to be remained and they take this bacteria in their gut and then leave the host. So from a few nematodes which actually kill the host the millions of these infective juniors will come out from the host in search of the new insect. Now there are some commercially available entomopathic nematodes they found in the US and the European in India also the efforts are being made in mass multiplying them and using agonist the several insect pest. Now let us look at the advantages of using these biocontrol agents what are the advantages of microbial agent as a component in IPM. So exploitation of the pest control is environmentally safe because of the host specificity you know because they are quite host specific so environmentally it is quite viable and microorganisms have a natural capability of causing episodic levels due to their persistence in soil and their efficient transmission. Once you actually release them in the field if the environment is quite congenial then they cause an episodics and results into a depth of large population of the insect pest. They are quite capable with chemical insecticide some of these can be safely mixed or they can be applied even when the chemicals are also sprayed so in that way they are quite safe. And the cost of development and registration of microbial insect is much less than that of the chemical insecticide and there is a large scale culture and application is possible and it is relatively easy and inexpensive and no resistance has been developed in this case or reported in this case. But factors which are affecting the biocontrol program or the tolerant limit of the crop to the insect injury it is successful in crops with a high tolerance limit and crop value it is quite good like where it has got a successful crop with a high economic value and crop duration if the crop has got a longer duration there it is quite successful and indigenous or the exotic pest. Again these microbials or the biocontrol agents works well when they are actually against the exotic pest in fact. If alternative hosts are available for natural enemies then the control of target pest will be less. As a result they should actually be quite species specific and in case of unfavorable season occurs then the reintroduction of the natural enemy is required and presence of hyper parasitide sometimes reduces the effectiveness of the biocontrol and the tritrophic interaction of the plant, pest and natural enemy sometimes affect the success of biocontrol agent. So for example like if the trichogramma which is released as an egg parasitoid against helicoarpa will work very well in case of tomato ecosystem than in the corn ecosystem. Then use of pesticide sometimes will affect the natural enemies and suppress their multiplication since we need to go for quite selective insecticides and identical situation for the successful control does not occur. That means to say that if the biocontrol program has successful in one region we cannot expect that it is going to be successful in all the regions. So it mainly depends upon so the many other factors abiotic and biotic factors for their successfulness. Then what are the limitations of this biocontrol? The biocontrol program usually what happens is in spite of a classic control that we get the pest population will continue to exist at a level which is determined by the properties of the host. So as a result so we cannot expect that so it will be completely below an economic injury level. The effectiveness of the natural enemies must be considered related to the man's economic threshold level. So that is way so we have to make an balance between see the economic returns of the crop and while using this biocontrol agent. And attainment of biocontrol of one of the major pest on a crop necessitates an elaboration of a system of integrated control of other pest of a crop in the sense because we are going to concentrate on a particular species of insect for managing. So we need to look for the other methods also for managing the other pest. So that is why a biocontrol can act as one of the important component in IPM so rather than as a major or a major component in managing the pest. So in this class we learnt about the important biocontrol agent as endopathogenic nematode and certain advantages and the limitations of biocontrol program. Thank you.