Post navigation

Ask a Grower

Ask-a-Grower #146 – How to kill gnats without harming the plant

I’m a first time grower and I got these little gnats in the soil. What do I do to kill them and not harm the plant?

Those little things are most likely fungus gnats.  They are not the worst pest to get but are still a pain.  There are a few products you can use in hydro or soil.  I use Azamax and SNS 203. They both can be used in soil or hydro and can be used as a foliage spray and a root drench.  You can actually run Azamax in a hydro reservoir.  Just remember always spray plants with lights off, unless you are using a “wetting” agent like Dutch Master Saturator.

Even though I recommend using foliage sprays, you are still going to want to do a root drench to kill the gnat’s larvae.  They breed in the root zone and actually feed on your roots.  I root drench 2 times a week for a couple weeks.  Then throughout the life of the plants I spray the top of the soil or rock wool or coco or whatever growing media I am using. This is just a light spray to keep any bugs away.  I hope this has been helpful. If you have any more questions please email ask-a-grower@ or call 619.796.1857.

What’s root drench?

A root drench is when you physically “drench” the root zone.  I would make up my water and either SNS 203 or Azamax, and then I would water the plants with this solution.  You can “top feed” (which is just watering the plants from the top of the growing medium), or you can dunk or flood the root zone.  Flooding or full root dunks are usually done for hydro systems.  Either way the object is to get the insecticide to the roots.  I hope this cleared up any confusion and as always please email ask-a-grower@ or call 619.796.1857 for any more questions.

16 thoughts on “Ask-a-Grower #146 – How to kill gnats without harming the plant

Leave a Reply

Your email address will not be published.