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How Bt Kills: The Science Behind Bacillus thuringiensis · Hydroponics Daily

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  Hello there and welcome back to
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  Hydroponics Daily, your go-to podcast for everything soilless cultivation.
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  I'm your host Dr. Russell Sharp from Utrema Limited.
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  We manufacture a range of fertilizers, biostimulants, biopesticides.
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  However, one biopesticide that we do not manufacture is Bacillus therugiensis or BT bacteria.
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  But this is one of the most common bacterial bioinsecticides
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  used globally and it
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  is pretty effective and safe to
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  use so i thought we're going to the really interesting way it works and
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  why it's safe to use on crops but is
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  actually very very toxic to insects it's
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  really interesting so stay tuned so i
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  will shorten the name of bacillus thuringiensis to
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  just bt from now on and bt is
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  a naturally occurring soil bacterium so single-celled
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  organism that's been studied for over a century and
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  what makes it so special is that it produces a type of protein called
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  cry proteins and these are
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  toxic to certain groups of insects especially caterpillars
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  beetle larvae and mosquitoes
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  as well so some plant pests and
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  some human plant pests so how does it work well when the insect larvae eats
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  plant material treated with the bt bacteria that can have the bt bacteria and
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  these proteins in them those proteins activate in the insect's gut they bind
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  to receptors in the gut lining punch holes into the cells and essentially stop
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  the insect from feeding.
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  Within a few hours, the pest is immobilised and it dies soon afterwards,
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  just as you would if your stomach had been punched holes in.
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  Crucially, the mechanism is very selective, Croke.
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  Selective and the cryoproteins only affect insects with
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  the right receptors in their digestive system humans animals
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  and beneficial insects and bees don't have
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  these receptors which is why bt has an excellent safety record okay so reasons
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  why it's been adopted by both conventional and organic agriculture is it's specific
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  to the pest it breaks down quickly in the environment so it doesn't persist
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  on the crop or accumulate in the soil.
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  And thirdly, BT has been used since the 1950s with no evidence of any risk to human health.
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  So if you've ever bought organic fruit or vegetables in the US or in most countries,
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  then BT will have played a role in protecting that crop.
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  In the UK, there are about 14 different products that contain Bacillus therugiensis.
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  The specific strain is azawa gc91 but
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  that's not important there's a couple of different strains
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  actually these are only available to commercial growers
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  and not to amateur growers at
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  the moment you can buy bt bacteria on ebay
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  and things like places like this but it's not registered for use on on
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  crops and so those products are very very
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  much in the gray area of of products you
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  can use in hydro because they're not registered but they
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  are the and they you don't know whether they're coming from a
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  trusted source they might just be these commercial products that
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  are re-bottled or divided up
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  things like that so they they're used in
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  a wide range of crops apples aubergines courgettes cucumbers
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  whole host of different ones the main reason they're so safe for use in humans
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  and there's never any accidental damage is because the cry proteins are activated
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  in alkaline ph so seven to ten and a half and insects actually use alkaline solutions to digest.
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  Plant material just like when we're digesting seaweed
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  extracts if you wanted to digest it seaweed you
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  know is to make a biostimulant often they use alkaline chemicals
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  the same process in an insect's guts they use alkaline solutions to digest plant
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  material whereas in your stomach you don't use alkaline you use acid and so
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  your stomach is ph1 and so there's no way the cryoprotein can get activated.
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  It's a really, really belt and braces way of preventing any contamination or issues.
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  So that's interesting from that perspective. We've talked about genetically
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  modified crops and that's at the other end of the spectrum here.
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  We've talked about organic crops and then GM crops
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  and the same technology that's used to
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  produce organic crops and this biomeceticide
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  is also used in many gm crops it's
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  not just weed weed killer resistance that is
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  the common one the glyphosate resistant crops
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  bt crops are really really common now one of the very first commercial crops
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  that proved really popular and so gm crops like bt maize and bt cotton you might
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  have heard of in these crops the gene and i think it's only one or two genes
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  from the bt bacterias are inserted into the plant genome,
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  allowing the plant itself to produce the cry protein.
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  And the advantage of this over the bacteria is its continuous protection.
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  The insect pest only needs to take a single bite of the plant tissue and the protein does the rest.
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  This reduces the need for repeated spray spraying and has a siphonic impact
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  on yield and pesticide use because you're not applying as many.
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  Pesticides and as with any gm technology
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  there are debates and consideration such as resistance management
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  and the regulatory framework you couldn't use
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  this in the uk for example currently or europe but
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  it is used widely in many other countries i think india and
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  america places like that and certainly china it's
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  grown on millions of hectares bt crops and there
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  are a number of considerations as well i'm not aware of any
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  bt gmbt crops used
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  in hydroponics but if you're aware of any then let
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  me know i guess some glass house crops are grown globally
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  that are genetically modified to contain the
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  bt cry protein so i thought that would be a good interesting
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  topic to discuss on hydroponics daily for one of the episodes if
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  you've got any thoughts or comments on bt your use of bacillus thuringiensis
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  then let me know it's not the only bacillus species
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  that is useful in hydroponics there's also bacillus
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  subtilis which has a number of different actions it.
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  Can also help with resistance against fungal attack
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  and the other good thing about bacillus whether it's
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  an insecticide or a fungicide or a biostimulant they are
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  very what's the word tough you know if you
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  have a powdered bacillus product it will survive a long time whereas
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  you have a nitrogen fixing bacteria it will die very very
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  quickly so if you ever pick up a bottle and it says contains nitrogen fixing
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  bacteria if it's been imported from america sat on a shelf in agrarian for a
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  long time you chances are it's dead and something like azotabacter will die
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  very quickly whereas a bacillus in a powder form lasts a long time so that's
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  another good reason it shows efficacy when it's applied to the crop.
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  Other updates on my microgreens. I've just brought my pea shoots and my basil
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  out to put on my new tray, on my new racking. They're looking fantastic.
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  And all the shop-bought seeds from the health shop I bought, they all germinated.
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  So that's great because I can now buy cheap seed from my local health food shop.
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  So the chia seeds did really well. The popcorn did really well,
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  so a lot of golden popcorn.
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  The spelt wheat germinated. the mung beans
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  the peas the only one
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  that oh the linseed did as well yeah the linseed did really well
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  the only one that didn't work was the quinoa or
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  quinoa as i like to call it very very poor germination on
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  the quinoa and so yeah i'm
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  not i won't be pursuing that i've got plenty of other healthy seeds
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  to grow so yeah i'll go back to the health
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  food shop buy more seeds and see which ones work
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  and i'll let you know there so the
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  number of microgreens we're growing is increasing dramatically and
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  so it'll be microgreens on toast in
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  the utremer hq for the time being thank you very much for listening for today's
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  episode as always the best thing you can do if you want to help the show is
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  leave an apple podcast review because that shoots us up the charts dramatically
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  as soon as you've done that until tomorrow thank you very much for listening and goodbye.