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Fungus Gnats: a major pest in hydroponics and houseplants · Hydroponics Daily

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  Welcome back to Hydroponics Daily with me, Dr Russell Sharp.
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  Today we're talking about a very common pest in hydroponics,
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  houseplants and horticulture in general and that is fungus gnats or as they're
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  also called scarred flies.
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  Stick around to the end because I'll talk about an amazing new way of controlling
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  scarred flies that I'm inventing and developing here in the Eutrema laboratories.
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  So I said scarred flies, they're also, they all belong,
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  there's a number of different species and they all belong to the scaridae
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  family the most common one in the uk is bradesia
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  deformis so there's two scientific names there for
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  you already it won't be that too heavy on scientific names
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  but i'm just putting them in there because i'm testing the ai bot
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  that is summarizing all our podcasts it's been performing extremely
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  well i've been very impressed with it so far getting scientific names correct
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  and so i'm going to put about five scientific names
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  in this one and see if it gets them right so as i said the
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  most common species of fungus that in the uk is bradesia deformus
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  they all look exactly the same though and
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  they all are treated and and act in
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  the same way they've all got the same life cycle it's just one will
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  have a slightly different look the leaves will be slightly different shape and
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  stuff like that to the others so as the name suggests they eat fungus so might
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  on the face of it be not too much of a problem however they can also eat young
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  roots and if they're eating mycorrhiza then they're also harming a friend of your plants.
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  And so they thrive in damp decaying
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  compost and growing media but you
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  can also get them in inert media because there will be fungus growing
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  on it algae growing on it that they can feed off the it's
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  the larvae that are doing the feeding so the maggots because they're
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  a fly so the tiny little maggots that are
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  doing the feeding and they're attracted to the
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  odor of damp decaying grow media you might not think your grow media is decaying
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  but a cocoa compost peat it will be decaying if it's waterlogged so first method
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  of control is obviously don't water every single day to contain a capacity do
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  what's optimum for your plants.
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  And then one area where my colleague Matt and I differ dramatically is I always
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  pot from one size pot to the next to the next to the next as I fill the plants.
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  That's to prevent transplant shock and also to make sure there's not too much
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  wet, decaying compost around a young plant.
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  Whereas Matt likes to put his seedlings into the pot they'll eventually end
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  up. And I think that is a recipe for fungus gnats.
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  But obviously there are advantages in that method. it
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  makes sure they're never root restricted until they come into
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  flowering and you only get transplant
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  shot once so let's go into the
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  methods of control so let's say let's go do the life cycle of fungus
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  gnats so it starts off as an egg they pupate
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  into a maggot and and sorry
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  they emerge as a maggot then pupate and then they form this
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  black fly that hovers around the plants the
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  surface of the soil and is looking for fresh
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  plants to invade and the populations can increase dramatically
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  very quickly so you can get thousands and thousands and
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  thousands of fungus gnats and it becomes as
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  much of a problem for your plant roots as it is an annoyance
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  they are become very annoying to have no one
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  wants to have flies around their grow room and so
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  the first thing that you should do is put out sticky traps
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  and obviously as i said previously black traps are the best but because of economies
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  of scale yellow traps do just as well and a top tip get the big rectangle yellow
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  sticky traps and then just cut them up and then stick them with the polybutane sticky stuff.
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  Directly to the the edge of the plant pots and then they will fungus gnats will naturally.
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  Get attached to them as i said in the last episode increase the airflow and
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  the fungus gnats will just get whirled around the growing room they won't be
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  able to control where they go and then they'll just get stuck on the trap and
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  then if you position your your outflow fan.
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  Close to the soil surface or below they'll get sucked into it they'll get sucked
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  off out into your out of your growing room,
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  other let's say physical modes of control you
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  could put diatomaceous earth which is or zeolites
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  these are like materials that fungus gnats
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  don't like on the top of the soil surface and this
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  will put them off the the
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  sense of the the damp growing media below and they'll
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  struggle to get through that to the to the growing media there's they go by
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  a number of trade names but that's what they are they're either zeolite or diatomaceous
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  earth chemical control you can go for a common insecticide like pyrethroids
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  pyrethrum so that pyrethrum is from a african,
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  chrysanthemum and then pyrethroids are chemically derived
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  different to this slightly different they're synthetic
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  there's a company called cx horticulture who
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  have a product called tanlin which is a various it's
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  allowed to be used in certain countries it's called tanlin because if you
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  spell it backwards it means nil nat and so they sell it don't know if they sell
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  it as a direct fungus neck killer but it's that's what it's you know that certainly
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  it's been sold as in the past i believe the active ingredient is chitin or chitosan
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  i think it's chitin we sell chitin and chitosan here at utreema.
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  Far higher concentrations but we never recommend it's used for
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  fungus gnats control even though potentially we
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  could because this is what the active ingredient in tannin is i
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  just don't see how there is a mode of action how
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  chitazan or chitin can really give
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  good control of fungus gnats you can say that it stimulates
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  chitinolytic bacteria and fungi in
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  the soil that degrade the the maggots but that's
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  a pretty long shot we prefer to
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  look at soil sterilants so organic soil
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  sterilants that will kill fungus gnats instantly and then
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  the use of yellow sticky traps so if you're
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  looking for a soil sterilant that can be used in hydroponics get in touch with
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  us we don't recommend it for house plants because it's hazardous for use so
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  we don't like to recommend hazardous products for house plants but when they
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  can be used safely and keep used in an organic system in horticulture and hydroponics,
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  then that's where we recommend them.
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  In a house plant situation, I'd probably go for either a nematode or a parasitic mite.
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  So a couple of good scientific names to test the AI bot.
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  The biological nematode that's used is Stenamifeltenae.
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  No i can't get this right at all anyway that nematode it's the nematode that's used for all,
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  fly-based pests so if you've got and
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  also a lot of beetle-based pests i think as
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  well so it's a very common nematode the actual strain
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  might be different for different pests the problem with nematodes
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  is they have to be applied at the correct soil temperature so they don't work
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  very well in the garden if it's cold but in a grow
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  room they should work very well and they're really
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  good to get under a microscope and have a look because you might think
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  oh this is a lot and you can see if they're alive or not you just stick them
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  in some water and you will see millions and millions of nematodes wriggling
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  around if they're alive i think it's basf that makes them i think they're made
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  in england it was one of the very first biological pesticides to be made and
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  being an English innovation.
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  It was quickly sold off to a multinational company.
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  There are issues around supply. The nematode that is good for slug control,
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  Phasma Haberditas hermaphroditae. Off the top of my head, that one.
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  People can struggle to get it in spring because the supply is so limited.
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  If you can get the nematodes, it might be worth trying that.
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  The mites, the predatory mites that eat the.
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  Maggots they are normally available 12 24 7
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  365 common species there is hypoapsis miles
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  hypoaspis miles i've grown
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  that mite in the lab here as well
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  so you can culture it as well if you know what you're
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  doing and so you can keep a ready supply it's it
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  is quite difficult though and if you're not careful you'll
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  you'll cultivate fungus gnats as well because and that's
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  what you definitely don't want to do because you have to you have
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  to put them in the compost that is wet and then decompose
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  in a bit and then culture them on the specific culture method
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  and things like this so yeah maybe just
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  buy that from the shop along with some nematodes if
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  you want to play around with some chitazine we can play with some chitazine but
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  i would probably go for a soil sterilant and i did say
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  we're working on a new one i've got this bit of
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  a heath robinson contraption in the office and it
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  involves decomposing grow media
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  that's kept purposely wet and it's and it's
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  like a little trap below one of those
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  traps that you would normally find in a delicatessen in
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  a supermarket that electrocutes blue bottles i've
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  taken all the uv lights out of it that would normally attract you
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  blue bottles and kept it dark and damp and
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  obviously keeping the moist grow media away from the electrical bits.
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  And the idea is that the the fungus gnats
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  in the grow room get attracted to this really
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  decomposing ground media and then on their way down hit
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  one of these wires and get electrocuted one of
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  my colleagues who didn't know about this trap was just sat
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  there having a rest having a drink and fungus
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  nut hit one of these electrical bars and it got the shock
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  of his life as it got electrocuted because he didn't know what it was obviously.
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  That's not been commercialized yet and if you don't know
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  what you're doing don't mess around with electricity and water but certainly something
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  we've enjoyed playing with here in the eutreema labs when
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  we've been testing it out and that's that so keep
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  your growing media not too wet what do
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  others say doesn't seem to be affected by ph or
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  anything like that and that's about it really fungus
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  gnats so or scarred flies if you've
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  got any other comments please let me know please click the
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  of when there's another episode and feel free to listen
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  back to any of the previous episodes at your leisure we've
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  now done over 100 episodes of hydroponics
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  daily which is a bit of a it's been a bit of a mammoth task
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  but it's been highly enjoyable so we'll be going for
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  some time yet hopefully at least until the end
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  of december so and we're gonna i'm gonna be doing
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  a lot of episodes from events as well
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  so things like green tech and might
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  even go to cultivate in ohio later in the year and grow tech in turkey that's
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  another one we're going to we'll go to fruit not fruit logistica there's one
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  in in spain anyway we'll probably go into in madrid so until then till tomorrow
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  tuesday thank you very much for listening that's been hydroponics daily.