Black flies swarming a planter box

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Hello everyone
In one of our large planter boxes there is thousands if little black flies. I am not sure what it is and how to eradicate it.
Any help would be appreciated
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Welcome to the forum.
I am the other end of the world and on another continent, so I am guessing a little. My guess is that they are some sort of midge or gnat, and the larva are living in the soil. You see them when they hatch out. If you water with one part 3% household peroxide (not the strong industrial stuff) to five parts water it should kill the larvae in the soil.
 
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Thank you very much for the reply.
I am quite desperate so will try that. Will it kill the plants? And will the soil be fine?
 
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Looks like a soldier fly but with a brown back. Maybe just immature?

I put my chicken poop in a pile and about summer time it is loaded with black soldier fly larvae. They compost the manure very quickly. Your soil must be rich in organic material.
 
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1 part 3% hydrogen peroxide, 5 parts water = 0.5% hydrogen peroxide. Shouldn't hurt your plant. I've soil drenched with higher strengths. I didn't know it would kill larvae though.
 
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Peroxide is H2O2, it easily loses that extra atom of oxygen to make H2O, water, and adds the oxygen to something else, so no, adding an extra oxygen where it will stick is not going to be harmful to the soil, oxides are not poisonous, but if it is a living thing like a larvae ...
 
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I use it kill fungi and to aerate the soil. Waterlogged soil is one example to avoid root rot.

Higher strengths of hydrogen peroxide can kill your plant but I've actually soil drenched with straight 3% hydrogen peroxide before. It did seem to stunt the plant but not kill it. The plant eventually started to grow again and produce but it was noticably behind the other plants right next to it that didn't get drenched.

I don't know if it kills bacteria or not at those strengths. If it does, and if you think about it, bateria is what converts organic nitrogen into plant usuable nitrogen so would the transformation happen? Maybe that is what stunted the plant... I killed the bacteria so then nitrogen wasn't usuable for a while? Maybe the hydrogen peroxide oxidized the plant usuable nitrates into a non usuable form?
 
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I just now have seen this old thread and no one has answered it. These bugs name is Plecia nearctica aka Love Bugs. They are harmless to plants but can be an EXTREME NUISANCE. When they mate they do mate it is in huge swarms, sometimes so thick that it clogs up the radiator of an automobile resulting in overheating. I had no idea they were in South Africa though.

 

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Yep, that's love bugs alright. Good call Chuck.

The good news is they are harmless to plants, but the bad news is they can overpopulate to the extent to be a real pest. We have a spring and a fall explosion of them every year with fall seeming to be the worst. They make a real mess of vehicles that have to plow through them on the highways. Good for car wash business.
 

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