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Hey crew!  Like many growers, I get fungus gnats in my grow from time to time.  I often bring bags of compost or worm castings into my grow, which means I regularly risk bringing gnats or other pests in from the outside.  I also often have bags or totes of soil or compost in storage around my grow, which creates a lot of potential sites for pests to hide out.

In the past, I’ve relied mostly on sticky traps, nematodes and BTi to control the issue.  For the most part it has worked to keep the gnats in check, but lately I’ve been using compost and castings a lot more often, and my old practices haven’t been enough to keep up with the constant threat of gnat invasion.


How do you defend against invasion?




Rove Beetles (Dalotia coriaria)

I absolutely love these little guys!  They are like little soil commandos!  Open the bottle of these guys and off they go!  Zipping around the soil looking for gnat larvae or other tasty prey to brutally devour!  RAWR!

Within a week or so of deploying these guys my fungus gnat populations dropped off big time.  I’ve only used them for fungus gnats, but I’ve read they are also effective for preventing root aphids and other soil pests.

They are commonly sold in bottles of 100, but in my experience, these bottles probably have several hundred little beetles in them.  No idea where they got the number 100 from… there has been a lot more than 100 in every bottle I’ve received.

I released a tube of “100” of these guys about 3 months ago and they are still alive and thriving.  They lay eggs that hatch little larval versions of themselves and they are happily reproducing and spreading throughout my soil.  If anything, the population seems to have increased over the last few months.

I recently added a bunch of new soil into my grow so I did a second release of two vials of “100”.  They are now quite abundant and easy to find in all my pots.  I’m hoping to keep the population going permanently.

My first order of “100” was from Natural Enemies Biocontrols and it cost me $23.  Natural Enemies has a $100 minimum order, so this was part of a larger order.  Shipping was $25 for my whole order.  Shipping was overnight but it took about a week for my order to ship.

My second order was for two vials of “100” and was from Green Methods.  They have a deal where you can get two vials of “100” for $25.  They have no minimum order.  Shipping was $21.  I placed my order on Friday and it showed up on Tuesday, so Green Methods gets bonus points for speed!

Both orders went smoothly and I can fully recommend both companies.  For a smaller grow, Green Methods is probably a better option since they have no minimum order requirement.

Stratiolaelaps scimitus (AKA- Hypoaspis miles)

I’ve also been deploying these little soil mites to defeat my gnat enemies.

They are a lot smaller than rove beetles, and look a bit like brown or tan colored spider mites.  Do not be alarmed though, these little guys live in the soil and don’t feed on plants.  They do feed on lots of bad guys though, including thrips, fungus gnats and root aphid larvae.

These little critters crawl around the soil and explore the mulch layer looking for prey.  They have a quick life cycle (13 days!) and will reproduce rapidly.  They’ve established themselves quite well in all my pots and have spread rapidly.

3 months after the first release, they are still thriving.  Peel away the mulch layer and you can see them happily patrolling the soil:

Its nice to know my soil is not just full of micro-life, its full of macro-life too!

My first order was again from Natural Enemies Biocontrols and cost $28 for a 1 liter tube of 25,000.  Natural Enemies has a $100 minimum order, so this was part of a larger order.  Shipping was $25 for my whole order.  Shipping was overnight but it took about a week for my order to ship.

I also ordered some from Green Methods.  I ordered 25,000 for $30.95, but they also have smaller and larger sizes available.  Shipping was $21 for my whole order.  I placed my order on Friday and it showed up on Tuesday, so once again, Green Methods  gets bonus points for speed!


  • Soil predators are awesome!
  • They are an effective way to prevent or combat soil dwelling pests.
  • They will establish themselves in a living soil system, and will stick around even after the pests are gone.
  • This makes them especially cost effective for growers that plan on re-using their soil for several cycles.  (no-till)
  • Ordering live insects requires expensive overnight shipping.  Consider teaming up with friends to place a group order to save on shipping costs.
  • Natural Enemies Biocontrols and Green Methods are both “Soup Approved” predator dealers.

Thanks for reading!