nm0217: okay think we've probably got a quorum er we er we're going to be recorded for posterity today ss: oh nm0217: do you want to say do you want to say something about what you're doing do you mind om0218: yeah er well i'm working at CALS which is next door Centre for Applied Studies and and we work with international students who entering the university trying to help them to prepare for listening to lectures and writing er assignments and so on and i'm going round the university collecting recordings of lectures in different departments so that i can have a look at the kinds of language that's used in lectures so then we hope we can improve our teaching [laughter] nm0217: yeah so we're going to be recorded for posterity on a C-D i think is it om0218: a minidisc yes nm0217: wow sf0219: ooh nm0217: technology so if any of you want to shout out Judas in the middle of the lecture [laughter] Bob Dylan fans would only understand that one [laughter] er it's quite ironic 'cause i got er at the end of the firs-, the student response for the first year module i did last term i got four-point- seven out of five for audibility of voice when i told my wife this she said she thought i was making it up 'cause she said i mumble all the time it's usually when i she says things like oh isn't it about time you painted that window sill with all the little teeth marks in i say yeah all right [laughter] so er anyway i'll try and be fairly er audible today er this also means that if there's anything we don't want to appear on the tape i can write it on the board and er [laughter] and see er now there's a slight change to the programme like the video i was going to show you today i lent to a student who of course hasn't returned it on time despite several reminders so er i'll have to show it to you er what i'll probably do is to you in week nine er when we've got tho-, in week nine on the timetable we've got debate preparation on that day i've got to give two lectures to the first years which i won't finish till eleven so what i'll probably do is have a have a meeting say for half an hour at eleven o'clock to discuss the debate the following week and then er i'll show you the video which is about forty-five minutes so we'll do that in week nine so what i've done instead today is i've picked out some more er slides so at the end of the two lectures today we're going to have er a couple of dozen slides to back up some of the things i'm going to talk about now we're going to do er th-, th-, in fact we're going to do three topics today er before the coffee break i'm going to talk about pesticides and then after the coffee break i'm going to cover er introduce you to the concepts of risk assessment as they're used in environmental management and also in human health as well with special emphasis on the mad cow disease epidemic and its possible er the possible numbers of people who are going to be affected by er the human variant of mad cow disease which as you'll see from the handout could be anything from a hundred to several thousand the data at the moment isn't isn't concrete enough to make an accurate prediction and then i'm going to say something briefly about ecotoxicology which is the way in which we can try and assess the environmental effects of chemicals before they're released into the environment using standard test animals but i'll go into that in a lot more detail after the break okay so first of all we're going to look at er the c-, couple of pesticides with obviously an environmental emphasis now th-, th-, the most important thing to b-, bear in mind throughout the lecture really is pest is a human definition and a pest is simply a plant or an animal which is living where man doesn't want it to live er and the best example i like to use of this is er is moles er i quite like moles i think they're quite cuddly cute little animals but of course they're considered to be a pest and it's quite legal to poison them and trap them things like bats which i think are ugly little blighters [laughter] er have enormous protection and if you have bats in your loft bats in your belfry even you it's illegal to disturb them even if they're filling the the void of your loft space up with er bat droppings and you can't you can't disturb them and it's simply a er human perception of moles are not good and bats are good and er i saw this thing which has quite amused me which was er i'll put this back up in a second which was another thing from the innovations report er and it's a thing called the sonic mole chaser the idea is that it's an environmentally friendly way of getting rid of moles it says these what you do is you ram this thing into the ground and it le-, lets off a low frequency vibration and this annoys the moles and they move away [cough] and there's a little cartoon here of a mole disappearing presumably into next door's garden it says [laughter] these sil-, these silent and unobtrusive repellents are a humane way of persuading moles to leave the area it's recommended by the Northern the widely read Northern Gardener magazine [laughter] but the best one i heard was a er it was on the Gardeners' Question Time on the radio where apparently you if you want to get rid of moles what you do is you buy one of these Christmas cards or birthday cards that when you open it up it plays Greensleeves or something you take the little musical chip out of it these last for about three months apparently and you drop them down the hole and the moles get so annoyed or [laughter] that er [laughter] that er [laughter] that they they go into next door's garden and these things [laughter] last for about three months er and it's a sort of environmentally friendly way of er of getting rid of moles [laughter] and then three months later you just buy another one right now then er it might surprise you to know that most pesticides have not been developed to kill off insects and in fact the main thrust of the of the G-M crops the genetically modified crops research has been not to develop plants that resist insects although of course that is part of the research programme the main development is to do with the fact that most pesticides are used to kill off other plants and just to give you an sm0221: sorry can you repeat it nm0217: pardon sm0221: sorry can you repeat it nm0217: which bit sm0221: nm0217: er most sm0221: nm0217: er genetically modified crops sm0221: thank you nm0217: is that okay sm0221: nm0217: the whole [laughter] sentence right sm0222: sentence nm0217: er research into genetically modified crops you might think it was main- , mainly to do with developing crops that were resistant to insects sm0221: mm nm0217: the main in p-, but in fact the main t-, er traits that are being selected for are resistance to herbicides in plants okay sf0223: nm0217: and this is because in the U-K for example about eighty per cent of pesticide usage is for herbicides just for spraying for weeds and only about ten per cent is for fungicides and about ten per cent for insecticides and then a minor component for killing off other things for example pesticides for killing off rats of course are called rodenticides and i think you've probably heard quite a lot about that in the course already er for herbicides th-, the usage is mainly to do with er direct drilling where in the past er historical past of course farmers would have always ploughed their fields before they planted the crops to kill off the weeds now they can spray the fields and kill off the weeds and then plant the seeds directly in the ground without having to to plough the plough the field and this saves them an enormous amount of money in labour this is called direct drilling er fungicides are used mainly for seed dressings when you collect seeds from a crop to store for the following year if you store them in a in a barn or something they can go mouldy quite quickly so if you cover the seeds in a very thin layer of of fungicide and this prevents them from going mouldy this is the main use of fungicides in the U-K insecticides have a have a much smaller usage because there aren't any really major insect pests of crops and we don't in the U-K we don't get things like locusts swarms er coming in and it's only occasionally when you get things like Colorado beetles which is on the handout that i gave you arriving that er tha-, that you have to very seriously spray for insect pests so that's the sort of ratio that er of usage that you get now the ideal pest-killing chemical if it existed would do the following first of all it would only kill the target pest so if you have a pest problem you want your pesticide to be very specific to only target the specific thing that you're trying to kill off of course as we know that's not often er invariably not the case er they should have no short or long term health effects on non-target organisms and this of course includes people clearly you preferably don't want to kill off the natural predators of things so if you have had a problem with greenfly er aphids on a crop er clearly you don't want to kill off all the ladybirds because ladybirds eat lots of aphids lots of greenfly but if you spray the crop to kill off the aphids then you'll kill off their natural predators as well so the pest problem in the long term can in fact become worse so ideally you'd want to target a specific er specific organism that was causing the problem er the third factor is you'd want them to break down rapidly into harmless components better rub this off while i remember hadn't i [laughter] break down into harmless components so that you spray your or you apply your chemical to the crop it kills the pest and then it breaks down very quickly and er one as we'll see one of the problems of pesticides that were used s-, s-, historically in in the past was that many of them were extremely persistent you remember when we did the practical on D-D-T the D-D-T was shown to cause eggshell thinning eggshell thinning in birds of prey and i'll come back that to that in a bit more detail later on but the pesticides which are being developed nowadays tend to have a much shorter half-life in the environment and some of them will in fact break down instantly when they touch the soil so er they're very effective when you spray them but they break down very quickly so there aren't such long term effects a fourth er factor is quite important although difficult to control i mean i-, the ideal pe-, er pesticide should prevent the development of genetic resistance to target organisms and i'll come back to this in more detail later on but er there are several species of insects which have become resistant to a w-, a wide range of pesticides and these are have very difficult to control in the field without er massive applications of pesticides which become ecologically unacceptable finally er farmers of course are all in in a business as as we hear i-, increasingly nowadays and the use of pesticides should save money compared to making no effort to control pest species and er pesticides are relatively have been relatively cheap er and it's in the farm-, been in the farmer's interest to spray the crops very regularly without actually doing doing without the scientific back-up to to er know whether or not this er is an an effective way of controlling the pests sometimes you can get away with much fewer with with many fewer applications of pesticides if you look for example at the climate and the the weather conditions and er th-, the natural population fluctuations of the pests rather than just spraying say every on the first Monday of every month because your farmhand happens to have that allocated in his diary look at the population structure of the pests look at the weather what's the best time to spray to have the most effective effect rather than just er spraying just because it happens to be that time of the month okay now i want to say something very briefly about the different th-, the three main types of pesticide just to illustrate the sort of problems that you can have environmental problems that you can have now the most or one of the most effective herbicides that's a pesticide for killing other plants is a s-, chemical called two-four-five-T and this was very widely used in farming and was also unfortunately very widely used in the Vietnam War where it became known as Agent Orange and the American Army sprayed er vast areas of the Vietnamese jungle with two-four-five-T er in an attempt to actually wipe out the jungle completely so the Viet Cong had nowhere to hide couldn't hide in the jungle and l-, vast tracts of Vietnam were laid waste by the spraying of this chemical and unfortunately during the manufacturing process there's an impurity which evolves in the in the chemical process called dioxin and dioxin is extremely toxic and many of the American servicemen who were involved in spraying this chemical and also farm workers who were spraying two-four-five-T er got some symptoms of dioxin poisoning which is a general sort of er aching of the body aching of the limbs er acne develops on the skin you get quite severe acne er and eventually headaches er and er it can be quite dehabilitating of course what happened to the poor Vietnamese who were in the jungle when they got sprayed i mean they've got very badly affected as well so er the effects of dioxin ca-, er have been quite serious so one of the problems with pesticides is that can contain impurities which cause effects which are nothing to do with the er th-, th-, the pest-killing status er for fungicides there is an example quite a sev-, s-, er serious example in Iraq in nineteen-seventy where er seeds were dressed with mercury it was quite common a common practice to dress seeds with mercury as a fungicide ev-, even in the U-K up until er the early nineteen-nineties it was still legal to do this no doubt now it's been stopped but er in Iraq in nineteen-seventy er the mercury which had been dressed s-, w-, ha-, was by mistake sent to a bakery and er loads of bread were made out of this brea-, this these seeds and er before it was discovered er that that this had er had occurred er about a thousand people died of mercury poisoning and many others were er dehabilitated by the mercury so you have to be very careful with these things with er that that that that they don't get move in the wrong direction in the food chain okay now thirdly insecticides er insecticides have been again very widely used and they're they've been studied quite intensively because of their potential effects on er high levels in the food chain and historically chemicals like D-D- T which were developed er some some years ago now have have had a long half- life so D-D-T technically has a half-life of two-point-eight years and the ninety-five per cent breakdown is about ten years but er this can be much longer if the D-D-T is in a a cold environment or a dry environment th-, the breakdown is very affecti-, er is very er affected by the temperature and the climatic conditions so these this is a sort of average figure it can be much longer now more modern insecticides like aldrin er have a much shorter half- life and they tend to break down more quickly and the very modern ones will break down often in a period of days and of course the problem with these insecticides is that they can accumulate in the food chain now you don't need to copy this down because you've had it on the er on the handout that i gave you for the practical but just to er reiterate again the problem about the eggshell thinning the er D-D-T which was used very widely for sp-, for spraying crops as an insecticide was accumulated through the food chain and er birds of prey like peregrine falcons and sparrow hawks which were eating er small small mammals and birds which had accumulated D-D-T [cough] became er badly affected because their the D-D-T would would interfere with the calcium metabolism of the birds so if you remember from the practical when we measured the egg eggshells er i've just put up the peregrine falcon data er we saw a thinning of the peregrine falcon eggs that had been removed from abandoned nests er in the sort of nineteen-fifties nineteen-sixties and there has quite been quite good recovery er in recent years although we did still find a few eggs that were were thinned okay so there can be impurities in these pesticides they can get er into the human food chain if if you're not very careful and the insecticides can also affect things if they pass up through the food chain now D-D-T it might interest you to know you'd think that D-D-T would have been banned but in fact this is an article from New Scientist on the eighteenth of September last year and it says here proposals to ban the pesticide D-D-T by two-thousand-and-seven have been dropped for fear of harming efforts to fight malaria instead countries negotiating to limit persistent organic pollutants agreed in Geneva last week to achieve elimination over time which is a good politician's fudge phrase on condition that poor countries get help finding alternatives er World Wide Fund for Nature says combinations of safer insecticides bed nets and draining of mosquito breeding areas control malaria just as well but the World Wildlife Fund dropped calls for a ban by two-thousand-and-seven because arguments over the date got in the way of the more important goal of helping poor countries adopt alternatives so the proposal to ban D-D-T by two-thousand- and-seven has in fact been dropped so D-D-T is still being used in er developing countries and of course if we have birds which er migrate like the osprey which migrate from Scotland down to er to Africa then they can pick up the D-D-T when they're in Africa and then when they come back to the U-K and start laying eggs that can cause problems if the eggshells are thinned okay so how are pesticides evolved there are three main generations of pesticides the third of which has arisen in the last few years but the first generation pesticides pesticides have been around for a very long time er before nineteen- forty which is a good sort of cut-off point pesticides were invariably natural products and the pesticide pyrethrum which is an extract from er flowers of a pyrethrum plant so you pick the the flowers from the pyrethrum plant er and they would be soaked in water and then you could spray that onto crops and the natural defence of the plant would also protect against insects and there's evidence that the Chinese were doing this er two-thousand years ago so many quite ancient cultures have been using pesticides for some considerable time but er s-, just bef-, before and after the Second World War there was a an explosion in the chemical industry er not an explosion expansion [laughter] in the chemi-, well probably was an explosion as well though w-, though i talk about explosions later on er there was a persistent er th-, th-, the persistent organ-, inorganic chemicals were developed and it was thought at the time that er in the sort of white heat of technology that existed that er this was the answer to all pesticide problems and that er if you had a pesticide problem you could just go and spray it with these chemicals and the problem would disappear of course as we know that hasn't happened er some of the chemicals which were used in in Victorian times were quite toxic and in up to relatively recent times er these include things like Bordeaux mixture which is named after the fact that it was used extensively for spraying vines in France grape vines and these are b-, basically just solutions of of metal salts like copper and arsenic and these are very persistent er and these would be sprayed on on crops and er would be quite good at resisting insect attack er i always think it's ironic that if you go a garden centre and you go to the organic sort of gardening section they include Bordeaux mixture as a traditional organic remedy which in fact it's probably about the worst thing you could spray on your on your garden because it is very persistent and er if you analyse soil from gardens and houses of more than say before about nineteen-ten nineteen-twenty they invariably have very high concentrations of er copper and lead and arsenic because people would traditionally just use this Bordeaux mixture as a traditional remedy er the house we used to live in off the Oxford Road in namex which was built in about nineteen-hundred i analysed the soil from from the back garden and it had about between five and ten times the normal background level of copper and it's almost certainly because people had been spraying Bordeaux mixture on their er on their roses or whatever they were growing there at er the turn of the century okay now the second generation pesticides which have developed from the Second World War onwards are mainly synthetic organic chemicals so for example D-D-T came into widespread use from nineteen-thirty-nine onwards and er it was a very important er chemical it it its n-, s-, it i-, er its use has certainly saved er millions of lives particularly for control in in wartime conditions where you get where you get high concentrations of people soldiers or refugees or whatever people in very impoverished conditions or difficult cramped conditions you can get diseases er diseases like er typhoid transmitted very easily and and if you have er mites for example which or lice which are transmitting the diseases er these were controlled quite effectively by D-D-T and er this this er had a big effect on er saving many a people's lives particularly during the war so although these chemicals clearly have have major problems environmentally they have saved a lot of lives now worldwide something like two-point-five-millions tons of second generation pesticides are used every year so the massive massive quantities it's a huge er industry which is economically is very important but er eighty-five per cent of these are used in the most developed countries like er America and Western Europe most farmers in developing countries don't er use as er pesticides very extensively because they're they're expensive and er there are cases of them being used locally of course but er in general most of the pesticides are used in developed countries er there are something like fifty-thousand different types of second generation pesticides which have been developed and of course this has implicatio-, environmental implications because it's really would be impossible to test every single pesticide on every single potential species in the wild and ways of getting around this problem i'll come back to later on when we we talk about ecotoxicology after the break so there are large numbers of of these chemicals and the usage is more or less the same as it is in the U-K about eighty-five per cent of herbicides o-, of c-, pesticides used in the world are herbicides and of that eighty-five per cent about twenty-five per cent sorry twenty per cent is used on golf courses and gardens i read some statistic once that said that five per cent of all herbicides in the world were sprayed on Japanese golf courses and they just drench them with chemicals to kill off the weeds so they have this very very particularly on the golf greens they have this very very pure er grass on a on a specific culture of grass which is mowed to within a couple of millimetres of the soil so the golfers can knock their balls in the holes another reason reason for banning golfers er [laughter] er ten per cent are used er for insecticides and about five per cent for fungicides so er again we can see that the vast majority of chemicals are used for er for herbicides now the third generation pesticides which have come into being in the last few years of course are genetically modified crops or G-M crops and if i asked any people in this room whether they would eat genetically modified crops i would guess that most people would say no they wouldn't and er the fact is that we've all eaten gemet-, genetically modified crops and we've been doing so for at least two or three years and this is because most of the soya that's used in er in food processing for a very very wide range of things like cakes baked beans er sauces er biscuits tons of things are made with the h-, have soya added as a as a part of the food er preparation process and most of the soya that's used is now genetically modified soya so we've all been eating it er whether or not we whether we like it or not and the main thrust for the development of the genetically modified crops is to develop crops which are resistant to herbicides which may sound rather peculiar but er the point of it is that if you can make your crop resistant to herbicides then you can spray er larger quantities of herbicides on a crop you can make them grow faster because you can get r-, rid of the weeds more easily er and this is because you cou-, if you for example if you spray twice as much herbicide on a herbicide resistant crop in theory you can get rid of the weeds twice as fast because your genetically resistant crop is able to survive much higher doses of herbicide this is very good for the the manufacturers of herbicides because they can sell more basically that's the that's the th-, idea behind the the problem and er on the handout one of the handouts i've given you this is er er on the one about Colorado beetle i-, i'll come back to Colorado beetles later on er the one that's on sideways on the bottom this is from yesterday's New Scientist so this this t-, course is nothing if not er topical and er there's a little article here which says resistance is useless and it's confirmed that in fact the major fear of the development of these herbicide resistant crops is that the genes for resistance can pass from the crops to the weeds if you then get weeds which are resistant to herbicides you can imagine the potential financial implications for farmers because if you er if you've got er weeds in a crop and you can no longer when you spray them with herbicides the weeds are no longer killed it means that you might have to go back to the er to a traditional method of farming again which is of course might be quite good but er but er has enormous economic implications now er in in America there well let's just do this where are we properly here we are if we look at er a couple of recent articles this is one from this is from Nature back in November this says er area under transgenic crops shoots up forty-four per cent it's the area of land planted with G-M crops is expected to increase dramatically particularly in China Argentina Canada and South Africa according to Monsanto the U-S agri-biotechnology company er the company said that almost forty-million hectares will be planted with G-M crops this year so we're not talking about a sort of fringe industry this has become a major thing er says G-M crops were planted commercially in Portugal and the Ukraine for the first time this year Teng was speaking at the Asian rice conference in the Philippines [laugh] so er worldwide these things are really taking off er but in the U-K er there is b-, a hol-, the British government has put a hold on it er there's a cartoon down here it looks like President Reagan actually i'm not sure as to who is it supposed to be but er [laugh] it says all we ask for is a level playing field with a r-, roller with genetically modified crops written on it squashing a squashing a butterfly er so the implication is that the the the the companies who develop these things are roller-coasting this thing through but as i said in the U-K there is now a voluntary ban on growing ge-, genetically modified crops in Britain until two- thousand-and-two so er that's that's been put on hold in the U-K but in the rest of the world it's it's really taking off and in America er more than half of of the acrea-, of the of the area growing certain c-, types of crops like er cotton for example are now genetically modified at least they include genes to make them resistant to to insects or resistant to herbicides okay now er what i thought i'd do next was to go through the major types of insecticides because er if you're reading around this subject which hopefully you you will er you'll come across these terms and it's useful to have the definitions in one place okay now the major types of insecticides are there's four main types there's first of all chlorinated hydrocarbons and er examples of these are D-D-T and aldrin they're also known as er organochlorines of course and the persistence of chlorinated hydrocarbons is quite high up to fifteen years or more okay the second type of insecticides are organophosphates we're sort of going through a sequence of of development here in terms of the t- , historically how they developed the the second type of insecticides are organophosphates and an example of an organophosphate is malathion and these are tend to be l-, these tend to be less persistent up to er to a year or so de- , again depending on the the sort of climatic conditions and then th-, the final two have low persistence carbamates er an example of which is carbaryl has a low persistence typically of weeks and pyrethroids again have a low persistence of days or weeks but er py-, most of the pyrethroids that are used now in farming are synthetic pyrethroids and er one of the ways in which these insecticides have been developed is that scientists have looked at the chemical structure the molecular structure of naturally occurring chemicals like pyrethrum and they have then synthesized a molecule which is very very similar but then th-, they've tweaked it to make it more toxic so what they did with the synthetic pyrethroids was to look at the chemical structure of pyrethrum which is a chemic-, a naturally occurring chemical in pyrethrum flowers [cough] synthesize it er synthesize it in the laboratory and then change change the structure of or slightly or maybe add or take off a hydrogen atom or something er and then test this and ma-, er to to find whether it's more toxic and the commercially available synthetic pyrethroids are more toxic to ins-, more toxic to insects than a naturally occurring pyrethrum t-, sf0223: change the nm0217: yeah sf0223: does that mean they can then patent it nm0217: er y-, er yes yes so then most of these chemicals are patented that's why there probably why there's fifty-thousand 'cause what they tend to do is they'll produce you know if they come up with a new chemical in the lab th-, er they might not have e-, any evidence that it's useful but if they patent it in ten years time sf0223: yeah nm0217: or at the end of the field trials they might find that it's useful 'cause these things take typically new chemicals nowadays and drugs as well take about ten years from discovery to final commercial approval because they have to go through a wide range of of er tests before they do that sf0224: with things like the chlorinated hydrocarbons and you say they're persistent can't you alter the persistence nm0217: yeah that's what these these more well organochlorines tend to be very stable molecules because of the the nature of the atoms sf0224: nm0217: yeah you and and it's difficult too that's why these new chemicals have been have been developed which are less persistent organochlorines in general are persistent chemicals just 'cause of the nature of the of the structure the of the chemical they're diffi-, more difficult to break down okay now the major types of herbicides are three main types of these er first of all contact herbicides an example of which is atrazine and these things you spray them on the crops and they will kill the foliage er because they block photosynthesis er second type of herbicides you get are sys-, so-called systemic herbicides and this is what two- four-five-T is it's a sys-, systemic herbicide and the systemic herbicides interfere with the natural hormones in the plants and essentially they make them grow too fast so the plants can't take in enough nutrients from the or water from the soil to make to sus-, sustain the very rapid growth rates that that they that are induced by the spraying of these chemicals and the third type are things called soil sterilants an example of which is trifluralin and this these chemicals will kill soil microbes essential for plant growth so if plants have mycorrhizal er fungi around the roots or if they're nitrogen-fixing for example these soil sterilants will kill off these microbes and the plants won't grow so well because they don't have this er symbiotic these symbiotic fungi or microbes around the roots so those are the main the main types okay now pesticides i've given them a pretty bad press so far but er of course pesticides can be are are have been very useful in a wide range of situations and if we just present the case for the defence for a s-, for a moment for a moment before we get on to the problems er pesticides have clearly saved er millions of lives controlling diseases er for example malaria the spraying of pesticides managed to ho-, con-, con-, contain m-, er malaria outbreaks quite successfully for er a number of years unfortunately we'll come we'll come back to this later but unfortunately of course er mosquitoes have m-, become resistant resistant to many of the pesticides that are used and in some ar-, areas malaria has returned er because of this resistance er the second point is that pesticides have er increased food production er lots of er er crops have been saved by the spraying of pesticides because they would otherwise have been eaten by insects er and it's estimi-, estimated that worldwide about er fifty per cent of all crops are lost to pests er incidentally another another twenty-five per cent is thrown away so of of the food which is grown in the world only about twenty-five per cent of it actually ends up in a inside us inside humans one of my ex er PhD students namex who er left a few years ago went to work for Tesco's because he w-, he realized that if he wanted his w-, he wanted a Porsche and he realized that if he stayed in academic life there was absolutely no chance and er so he went to work for Tesco's he's now in the working in the office which plans new Tesco's stores which is quite interesting anyway he was for a while when he was on the management training course they put him in charge of the fresh fruit department in Tesco's in Broadmead in Bristol which he said was like working in a prisoner of war camp or something he said it was just unbelievably stressful er for about eighteen months just to sort of test him out to make sure he could could hack it before they put him into the office and he said that they used to throw away about half of the f-, half of the fresh produce was thrown away only half of it was sold because things like tomatoes particularly more than half of the tomatoes that you see on the display that people pick out by themselves are thrown away because they s-, go past their sell-by date [cough] or because people damage them when they're handling them so on average about half of the food that's grown is lost to pests and of that that s-, survives about half of it is thrown away which is not good news really but er okay now one of the er major problems with using pesticides of course is the development of genetic resistance and something like five-hundred insect species are resistant to some insecticides and twenty insect species are resistant to some extent to all insecticides and this is a a clearly is a major problem er to to to put it into context er in the U-K there are periodically there are outbreaks of er scratching my head i shouldn't do that outbreaks of head lice instinctively scratching and er my children had it a couple of times when they were er you know when they were at sc-, school when they were about er think once when they were about six and once when they were about er ten er haven't had it for a quite a long time i should reassure you about that but er [laugh] so i don't have it now but er it's very widespread and you very often er friends of ours who've got children will often mention oh there was an outbreak of head lice at school today and head lice has re-emerged in the last fifteen t-, ten to fifteen years as a p-, as a problem and this is because the head lice have become resistant to the chemicals that are used in their control and er when our kids had head lice you have to go to to Boots the chemists and er buy some head lice lotion and you rub it some of you probably know about this who probably don't want to admit it but you have to rub it in your hair and leave it for a er half an hour or something then you wash it all out and then you have to do it the same thing again a week later to kill off the eggs or anything that's hatched out and er what they do in Boots o-, in all the chemists is there is a national programme to change the active ingredient in this shampoo er about every month or two and the idea behind it is to prevent the head lice from becoming resistant to one particular chemical so for one month they may use er malathion as the active ingredient and then a couple of months later they'll change from malathion to another chemical and the idea is to prevent the head lice from becoming resistant to to er to these insecticides the er the nowad-, in the last year or two head lice have become resistant to all the chemicals that have been used and it's now become very difficult to get rid of them and er people are recommending that you go back to the traditional methods of of of er combing with a very fine comb on a regular basis to try and get rid of them but it's not nothing like as effective as dousing them with chemicals so head lice is a is a m-, major problem at the moment another problem with pesticides of course is that you tend to kill off natural enemies if you spray a crop you'll kill off things like ladybirds and er fly larvae that are eating eating things and of course er you can kill off er wildlife and there are clearly threats to er to wildlife if you're spraying a crop particularly on a windy day less than ten per cent of the pesticide that you spray will settle on the crop most of it will get land on the soil or will get blown away to adjacent er land and if of course if you've got farming surrounding a nature reserve it's possible that you could get quite severe mortality of of er insects if the pesticide blows on to the nature reserve and of course there are threats [cough] excuse me to wildlife and humans through passage up through the food chain er f-, last of all the problems er you do get occasionally get major disasters the worst one that's occurred is the explosion which i referred to earlier on and this was at a place called Bhopal a Union Carbide factory in India and here three-thousand-three-hundred people were killed by release of thirty-six tons of methyl isocyanate gas this is in nineteen-eighty-four and about twenty-thousand serious injuries occurred so er you you can get major disasters that in with the chemical industry associated with er leakages of toxic chemicals of course cyanide is also in the news at the moment because of this there's a been a major release of cyanide from a gold mine in Romania and it's seems to have killed almost everything in the Danube in the last week or two okay now before we go on to look at a few slides what are alternative methods of pest control without using chemicals okay now the first of these is is biological control and with biological control you can encourage the na-, p-, instead of just spraying the pests you can encourage natural predators to try and bring the pests under control er for example you can now commercially buy little packets of of eggs of parasitic wasps which you can hang up among crops and when these hatch out these will parasitize the pests particularly er aphids and er they lay eggs inside the p-, the aphids and the aphids die because the larvae eat eat them eat them from the inside out but these methods really only work very well in glass houses where you can p-, where you can confine the pest and the predator or the parasite if you try it in the field the the the the the the density of the parasites isn't sufficiently high to control the pest because they tend to fly away so that works pretty well in er in glasshouses course you can also introduce diseases into pests er particularly virus diseases and this can also be ef-, effective and there's a thing called bacillo virus which is quite widely used commercially as a pesticide which contains a bacterial toxin which will kill off insect pests particularly caterpillars now another way which is quite a cunning way and this is a good example of where basic biological knowledge zoological knowledge is used in an applied sense and this is what's called insa-, insect sterilization and this has been quite effective in controlling a pest rather disgusting pest called the screw worm fly in America this fly lays its eggs on the back of a back of a cow and the larvae hatch out and then burrow through the skin of the cow and live in a sort of chamber underneath with a breathing hole it's a revolting sty-, lifestyle really and er and this apart from causing intense irritation to the cow er means that you can't sell the hide afterwards 'cause it's full of holes and what they do here is they will breed screw worm flies in the lab they expose them to irradiation and this sterilizes them so you end up with large numbers of sterile male flies er you then release thousands and thousands of these sterile flies into the field and they will mate with the females and of course because they're sterile the females' eggs are not fertilized and er when the females come to lay the eggs there are no larvae to hatch out and although this doesn't get rid of the problem completely it reduces it to such a low level that it becomes commercially viable er and is is a very good way of controlling the the pests now another way is to attract pests u-, er sort of hijacking their natural s-, er attractive attract er sexual attractant system and of course many species of moths er the males will be attracted to the females because the females give off this pheromone sort of come and get me chemical and what you can do is you can either you you can have a in the field you can have a you know like those er ultraviolet traps you get in butchers' shops and things and food shops with a ultraviolet light and an an electrified grille and the fly comes in and sort of oh there's a ultraviolet light and then go she-oo pssh whack zap you hear this crack as the thing gets instantly electrocuted well you can do the same thing with moths and you can put a a female moth behind one of these grilles and the males come flying in thinking thinking they're about to have sex and then they whack zap they get electrocuted on the electric grille [laughter] and er of course one female can attract hundreds thousands of males and er this is very effective at reducing the the er incidence of males in the population and can ha-, kind of be quite effective now there was something again in yesterday's New Scientist which is er very similar to this if you read the article you'll get it in more detail but the Colorado beetle which is a major pest of potatoes er they're suggesting er using the same technique but rather than using a sex attractant to find out what the active smell is in potato leaves and er again use this as a as a trap mechanism you put the the chemicals in a trap and er the Colorado beetles think oh it's a potato and they come flying in to the er to the trap and then of course they get killed because er because they're er 'cause it's not a potato a-, at all it's just a chemical to attract them and er f-, finally insect hormones er you can mess up the biochemistry of insects by spraying them with chemicals which mimic chemicals within their bodies er within ca-, er caterpillars for example there's a cormone called juvenile hormone and the animals secrete juvenile hormone until the end of the fifth instar and then it the juvenile hormone production stops and then they then pupate into a pupa and then of course into a butterfly or a moth if you spray the insects with these juvenile hormones or or mimics of the juvenile hormone synthetic versions of these hormones you can prevent the caterpillar from pupating so it gets to the fi-, fifth instar and then it just keeps growing moults into a sixth instar and eventually it will die because er because the other components of its biology think it's turning into a pupa when it's still a still a caterpillar so you can er target the pesticides to hit particular aspects of the biochemistry of the animal okay right final overhead before we er look at some slides whoops okay now this is a schematic er diagram don't want to er show you that yet schematic diagram which illustrates the principle of biological pest control if we have time along the X-axis and pest density along the Y-axis the purple line is the density of the pest and the orange line is the economic threshold if we can get the population of the pest well below the economic threshold then er then it's if there's a small amount of pest damage it doesn't really matter if the dif-, if the overall level of damage is acceptable so if you've got the pest density going along here it's clearly t-, above the economic threshold line which is too high er if we introduce some method of biological control some of the methods which we er mentioned above we can get the pest population to get down below the economic threshold and this means that we have to accept a small amount of pest damage but the damage is not sufficiently great to significantly affect the the income of the farmer but if we do biological control we have to accept some damage i'm giving away my age here but er most of you probably haven't heard of Joni mitch- , Joni Mitchell but there's a song that you hear ev-, every so often Big Yellow Taxi and one of the lines is give me spots on my apples but leave me the birds and the bees and er every time if you go shopping in the supermarket and you're picking out apples for example from a a big display of apples if you pick one up and it's got a small imperfection on it a hole or a small scab or something if you put it back you're encouraging the over-use of pesticides because you are only accepting perfect fruit and the environmental consequences of perfect fruit and vegetables is an increased use of pesticides so er we have to if we want to use less pesticides and use biologic-, biological control we have to be able to accept that er some of the things that we eat may not be er absolutely perfect okay let's look at some slides before we stop right has everybody finished with this yep okay about another ten minutes or so then you can have a sm0225: really nm0217: [laughter] what's s who said all right [laughter] can have a nice er er a coffee break right now then er of course pests as i said aren't just used for killing insects er this is a Forestry Commission plantation just south of Reading at a place called Heath Warren near Bramshill and when they clear the trees when they chop down the trees as a commercial product er what's left behind is er is a bare ground because the light doesn't penetrate very well here and you get a very rapid growth of things like birch trees and er general er low growing plants and they can control these by spraying and this is just an example here this is the an area which has been felled and after they've felled it er they put this notice up i've got a higher magnification picture of it here here we are er this is a this area has been sprayed to control weeds and there's a says herbicide applied do not eat fruit and there's a pi-, just in case you don't know what fruit looks like there's a [laughter] picture of it and er if you were a kid and you had an I Spy book I Spy Signs that would probably be worth about two- hundred marks [laughter] 'cause it's a 'cause it's a couple of blackberries with a line through so er they spray the area instead of going around for somebody physically going around and chopping all this stuff down it's obviously much cheaper for them to spray spray it er to allow the baby pine trees the chance to grow up because if they don't do that then the pine trees get er get smothered by this very rapid growing er vegetation now er one method of biological control is to encourage natural predators of pests to migrate into crops and in some farms nowadays the farmers will leave a strip quite a wide strip around the field and this acts as a reservoir for things like carabid beetles and er natural predators and during the night they can crawl from this area this refuge into the crop and er help to control the pests it's not a er a complete substitute for spraying but certainly it has been shown that there are significantly lower numbers of pests in the margins of these fields than there are in the centre and what th-, some of them er very organic farms do is they will put strips of these sort of set-aside strips right through the crop er so that the natural predators have a refuge all throughout the crop and this does significantly reduce the incidence of pests okay now just something briefly about the D-D-T problem er the D-D-T didn't didn't just affect birds of prey this is a picture of a a nest of a brown pelican and this is a double-crested cormorant which became deformed in the egg the egg managed to hatch but as it grew this the beak was very badly deformed you can see the upper part of the beak here is curled and here the eggs have become squashed by the female because the eggshells have become thin because of the interference with the calcium and metabolism by the D-D-T that was used in the area in the U-K er this is changes in the status of sparrow hawks in relation to agricultural land use this is a proportion of land which is farmed er intensively and you can see the black areas here in East Anglia particularly of very intensive farming and this is the er populations of sparrow hawks around the time when D-D-T was being used and you can see there's an almost mirror image here in the in the terms of the intensity of farming and the populations of sparrow hawks sparrow hawks manage to er persist qu-, in quite high populations in Wales and south-west England where the farming intensity is lowest but er during the maximum period of usage of D-D-T the sparrow hawks died out almost completely from East Anglia although now of course they've returned and er this illustrates the whole problem this is the same thing with peregrine falcons relative to nineteen- thirty you can see that the population of peregrines declined during the usage of er s-, these pesticides and has recovered quite substantially since the er D- D-T was in fact banned throughout the E-, European Community f-, in nineteen- eighty-one although in the U-K it was banned banned earlier than that and this is the eggshell thickness index er just reiterates what we saw on the overhead and we saw in the practical class that there was a distinct thinning during the period of maximum D-D-T use and that er if we relate the thickness of eggshells to the D-D-E content which is the er er metabolic breakdown product of D-D-T we can see there's a very clear correlation between the thickness of the eggshell and the concentration of D-D-E okay so now i just want to show some general slides to back up the idea of pests er this is over in chemistry this is the where the manic mole used to er [laugh] do its stuff there's a big huge ar-, there's this big area of daffodils which are about to come out now but er every so often the mole manages to get across the road and then it causes all these little er little hummocks but again it's a the concept to the fact that the moles are a pest because they're in an area that er the ground staff don't want them to be so they they're defined as a pest whereas if they were a t-, colony of bats living in the top of the er Chemistry department up here then we wouldn't be able to do anything about it because they'd be legally protected even though they might be covering the floor in er bat droppings [laugh] okay here's some more pests this is a er an example where you can have a an animal which has a natural its natural food er is a plant which grows wild in the environment but er if it manages to cross that barrier and start eating other plants then it becomes a serious pest this is a large white butterfly caterpillar which of course is a very er severe pest of cabbages but it will s-, will also eat nasturtiums this is a one on a nasturtium leaf in our back garden so these things can cres-, pests can cross er species barriers and eat er plants which they wouldn't naturally have evolved to here's another pest this is a sawfly larvae this is a larvae of a of a wasp rather than a moth or a butterfly and if you don't know the difference between them the way to tell the difference between a sawfly larvae and a caterpillar a butterfly or moth is that sawflies have seven pairs of prolegs one two three four five six seven as opposed to butterflies and moths which have five but er these sawfly larvae are quite serious pests of u-, of a range of crops and er when you annoy them they will exhibit this characteristic alarm behaviour which is to raise their bottoms in the air and er apparently it's supposed to to scare off er potential attackers okay er greenfly this is a w-, one of the main problems with aphids is that they can reproduce very rapidly and they can reproduce parthenogenetically which means that they don't have to have males the females can produce baby greenflies little baby greenfly here aren't they sweet sf0226: mm nm0217: [laughter] er without without mating with a male so they can increase their population density extremely rapidly er exponentially in fact er in under certain circumstances and of course if you spray the crops then you'll kill off the natural predators of of these things like two-spot and seven-spot ladybirds these here are munching their way through some er cherry aphids on a cherry er cherry tree in our b-, again in our back garden at home so they a ladybird can eat between fifty and eighty greenfly a day so they really are major er pests er major predators of pests here's another one this is a hoverfly larvae er sorry not a hoverfly larvae a lacewing larvae eating a eating a fly here and these again are major pests of er pred-, predators of of of pests particularly greenfly and here's one here this is a business end here which has grabbed on to this this er fly so all these things will get killed if you spray the crop with a general purpose insecticide okay now the-, wasps are good examples of animals which are most of us would consider to be pests but but in fact are on balance very very beneficial because they themselves will eat lots of pests this wasp here is in a place where i don't want it to be because it's it's er rasping its way through our garden bench and er when you're sitting out there in the summer reading a book or something you can hear this sort of scraping noise what the hell's that you look around and there's a wasp scraping away at the bench and er this is made of teak i should have environmentally friendly teak i should point out approved by Friends of the Earth so this must have about the hardest wasps' nest in namex 'cause it's scraping away the wood to take away to make its er make its nest but that's clearly in that situation the wasp is a pest er also if you get wasps on er apples they're a pest 'cause you might end up with er with one in your mouth but on balance wasps are very useful animals because they eat very large numbers of pests themselves okay this is a a head louse er which isn't from my hair i should point out it's from somebody who c-, who sent it to me and er if you remember these these er head lice have become very resistant in recent years to er to pesticides and er one of the problems is that they will lay their that you can rid of the the adults themselves but they lay eggs on the hair shafts and these eggs are very very resistant to the pesticides so you have to have two applications of the pesticide to kill off the the er the the baby head lice which hatch out of the out of out of the eggs okay flies most people would sco-, would consider flies to be pests but of course flies are er very important in decomposition and as maggot larvae er if we didn't have flies around then er we'd have dead bodies lying all over the place dead animals because flies are extremely important in breakdown of materials so it's another example of an animal which is a pest from one point of view in that you don't like them buzzing around anno-, getting on your food but if they were absent then there would be er real problems in terms of a slowdown in decomposition of dead animals it's just a load more there the pupae down here right finally this is today's joke anybody guess what that is fly in the ointment yeah er [laughter] right okay i think we'll stop there and if we restart at er do you want a long coffee break today sm0227: yeah nm0217: shall we restart at eleven ss: nm0217: okay