Black Flies a nuisance?

murihikukid · January 8, 2017

Hi...Is there a good way to get rid of black flies...These must be coming from soil within the house ...Most of my plants are now outside in a greenhouse but the flies are still inside....
I do have some seedlings and a propagator which I can move to another room if a spray is used ....These insects like Banana skins ???

Thanks Ron..

gorbelly · January 9, 2017

Sounds like they're either fungus gnats or fruit flies. You may have both, as I noted in your other thread that it sounded like you had a serious fungus gnat problem.

For fruit flies, you can buy traps, or you can make a homemade one. Make sure you always seal up your kitchen waste, don't leave fruit out, etc. so that they have no place to breed. Eventually, the adults will die, and if they have no fruit or veg waste to breed in, they'll disappear.

Fungus gnats are more stubborn. The best remedy if you don't want to go chemical is BTi (Bacillus thuringiensis var. israelensis). Note that this is NOT the same BT used to kill caterpillars. It's a different strain that targets different organisms.

BTi over here is sold as Gnatrol or Knock-out Gnats (granular form). You can also break up and use mosquito dunks/mosquito bits which also contain BTi. Use it as a drench and apply at every watering for every plant in the house for three weeks. Make sure it drenches the soil evenly.

In the meantime, sticky traps can help cut down on the adults of both fruit flies and fungus gnats.

In future, do not use moisture-retaining potting medium with a lot of organic material in it indoors. That's just asking for fungus gnats. Topping your houseplants' soil with a thick layer of sand and only watering from the bottom and only watering when needed, letting the surface of the soil dry out completely between waterings, will prevent a recurrence of the problem. When starting seedlings, use a sterile medium.

Fruit flies are harmless to plants, but fungus gnats can lead to damping off, and their larvae will devour the roots of young seedlings and can do serious damage.

murihikukid · January 9, 2017

gorbelly...Thanks for all the information ...so fungas gnats could result in serious root damage...I always check any plant that is finished with especially the roots and some plants lately have hardly any roots at all...and I wondered if there was a reason for this ...
Cheers on

gorbelly · January 9, 2017

The conventional wisdom is that fungus gnats are only dangerous to very young seedlings and not full-grown plants. But I tend to think after hearing other people's experiences and having dealt with them myself that they can at least stunt the growth of older plants, too, and certainly do enough damage to hamper nutritional uptake. I personally have seen pretty extensive damage on the roots of larger seedlings that have more than one set of true leaves. It probably depends on the plant as well.

But there's also the fact that damage from the fungus gnat maggots is difficult to separate from the damage from the environmental conditions they like. They like mucky, overly moist soil with lots of fungal organisms in it. That kind of soil can also lead to root rot, etc. So your problems could also have been due to root rot caused by too much watering or a potting medium that is too moisture-retentive.

Cole_Robbie · January 9, 2017

I personally have seen pretty extensive damage on the roots of larger seedlings

I absolutely agree. Fungus gnat larvae eat roots.

murihikukid · January 9, 2017

Quote:

Originally Posted by Cole_Robbie

I personally have seen pretty extensive damage on the roots of larger seedlings

I absolutely agree. Fungus gnat larvae eat roots.

Hell I hope its not that ..my new seedlings are really looking good..i have started using my 5 foot LED tubes ...These produce no heat so I can lower tham right down til they are basicly 1/2 inch away from the leaves without any worries of burning the small plants..They might be better out in the greenhouse now getting real light...
Cheers Ron
PS The straggly looking plant to the right of the window is one of my original Tasty Tom Cuttings ...it was raised and then transplanted on May 11th 2016 and has survived through everything including the bleach and is still producing tomatoes ..not many and they are small but I love that plant...Without it I would have given up a long time ago...

MuddyToes · January 14, 2017

Thanks, Gorbelly. I think fungus gnats have attacked my Meyer lemon tree.

January 8, 2017	#1
murihikukid Tomatovillian™ Join Date: Feb 2016 Location: Invercargill New Zealand Posts: 1,022	Black Flies a nuisance? Hi...Is there a good way to get rid of black flies...These must be coming from soil within the house ...Most of my plants are now outside in a greenhouse but the flies are still inside.... I do have some seedlings and a propagator which I can move to another room if a spray is used ....These insects like Banana skins ??? Thanks Ron..

January 9, 2017	#2
gorbelly Tomatovillian™ Join Date: Jul 2015 Location: Southeastern Pennsylvania Posts: 1,069	Sounds like they're either fungus gnats or fruit flies. You may have both, as I noted in your other thread that it sounded like you had a serious fungus gnat problem. For fruit flies, you can buy traps, or you can make a homemade one. Make sure you always seal up your kitchen waste, don't leave fruit out, etc. so that they have no place to breed. Eventually, the adults will die, and if they have no fruit or veg waste to breed in, they'll disappear. Fungus gnats are more stubborn. The best remedy if you don't want to go chemical is BTi (Bacillus thuringiensis var. israelensis). Note that this is NOT the same BT used to kill caterpillars. It's a different strain that targets different organisms. BTi over here is sold as Gnatrol or Knock-out Gnats (granular form). You can also break up and use mosquito dunks/mosquito bits which also contain BTi. Use it as a drench and apply at every watering for every plant in the house for three weeks. Make sure it drenches the soil evenly. In the meantime, sticky traps can help cut down on the adults of both fruit flies and fungus gnats. In future, do not use moisture-retaining potting medium with a lot of organic material in it indoors. That's just asking for fungus gnats. Topping your houseplants' soil with a thick layer of sand and only watering from the bottom and only watering when needed, letting the surface of the soil dry out completely between waterings, will prevent a recurrence of the problem. When starting seedlings, use a sterile medium. Fruit flies are harmless to plants, but fungus gnats can lead to damping off, and their larvae will devour the roots of young seedlings and can do serious damage.

January 9, 2017	#5
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	I personally have seen pretty extensive damage on the roots of larger seedlings I absolutely agree. Fungus gnat larvae eat roots.

January 14, 2017	#7
MuddyToes Tomatovillian™ Join Date: Sep 2016 Location: Delaware Posts: 234	Thanks, Gorbelly. I think fungus gnats have attacked my Meyer lemon tree.