Fungus Gnats & Thrips

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Pictured top:  Cucumeris consuming thrips larvae

Pictured bottom:  Stratiolaelaps consuming root weevil larvae


Stratiolaelaps (Hypoaspis) should be used only once, on new areas as an inoculation as they will stay in the soil for the life of the crop.  They are primarily purchased as fungus gnat egg and larvae predators, but they also help with thrips control by going after immature thrips pupae that live in the soil. This generalist mite will also go after diapausing pest mites when they leave the crop, and are a great treatment for immature stages of weevils that also live in the soil.


Nemasys should be used every 2 weeks up to 3 times to help break the life cycle of an established fungus gnat infestation.  The Nemasys are not very persistent so that is why follow up treatments are needed.  It can take up to 6 to 8 weeks for the adult population to crash, once 2 or 3 generations of larvae have been removed by the nematodes. 


However, if the room is not tight, and fungus gnats keep getting in, re-infestation will take place and they will continue to cycle.  And this also happens if there are areas of soil that are not treated, like walkways and under benches, for example.  They are hard to eradicate, but 

perhaps a reasonable goal is to focus on the larvae, as they cause the direct feeding damage to seedlings and young plant roots.  And in that case, you may have to decide to make it a regular practice to keep using the Nemasys.  Or you can decide, once plants are hardy and there is not much fear of disease through root feeding, to live with the adults and ignore them if they are just a nuisance and not truly causing damage.

Atheta (Dalotia), otherwise known as Rove Beetle, is another product you can consider to introduce against fungus gnats. Rove Beetles do best in very wet environments, as they mainly feed on shore flies and fungus gnats present in moist areas. They have a longer life cycle and take longer to establish, so should be introduced alongside Hypoaspis for the best results and effectiveness. One application of Atheta per crop cycle is sufficient if introduced early in the season, and can be applied to the soil in the center of your greenhouse/growing area.


However, we do have a much different strategy for dealing with thrips. 


Each life stage has to be approached differently.  Adults can be trapped on yellow sticky cards and tape, and shallow basins of water spiked with a few drops of soap and an aromatic scent (vanilla works well) will attract and drown many.


Cucumeris is an older biological control, but still one of the best. On a cost basis, there is no other thrips predator that even comes close.  You can apply cucumeris on foliage to eat young larvae that are on the leaves.


You can apply Hypoaspis (Stratiolaelaps) to the soil to help by consuming thrips pupae (and fungus gnat eggs and larvae) in the soil. Stratiolaelaps is a generalist soil predatory mite that is also capable of controlling fungus gnats,  springtails, root weevils, etc.


You can use the nematode Steinernema feltiae, called Nemasys, as either a foliar spray to help kill thrips adults, or as a soil drench to help with thrips pupae.  Nemasys is also very good on fungus gnat larvae control.  

The cucumeris and Hypoaspis each cover about 1000 square feet and come in a 1L tube, $45.00 each for either the cucumeris or for the Hypoaspis. The Nemasys comes in a pack that covers about 1000 - 1500 square feet. (one pack costs $75.00)  Nemasys come in packs that can be stored in the fridge for usually about 2 months, so you can buy more than 1 pack at a time for a repeated application.  Yellow sticky cards start at $15.00 for a small pack.


If your crop is young, we would recommend using all aforementioned biological controls. If the crop is near harvest, then concentrate on the cucumeris and Nemasys as a foliar spray, plus the use of cards to trap adults.

No one product is better than another, as each concentrates on a different life stage of the pest.

Click here to go to Applied Bio-nomics thrips technical manual

Click here to go to Applied Bio-nomics fungus gnats technical manual

No-Thrips (Neoseiulus cucumeris):

10,000 Mites (22690): $25.00 cover up to 500 sq. feet of foliage

1L tube (50,000 mites) (22700): $45.00 suited for areas 1,000-2,000 sq. ft.

            Buy 3 or more: $35.00/1L

Hype-O (Stratiolaelaps scimitus / Hypoaspis miles):

3,000 Mites (22742): $19.00 suited for areas up to 200 square feet

1L tube (25,000 mites) (22740): $45.00 for areas 1,000-2,000 square feet

            Buy 3 or more: $35.00/1L

Nemasys (Steinernema feltiae):

50 million (25250): $75.00 suited for areas of 550 to 1,650 square feet

              Buy 3 or more: $65.00 

Yellow Sticky Cards:

Pack of 10 (10 x 25 cm ea.) (23800): $15.00 

Pack of 100 (10 x 12.5 cm ea.) (23795): $65.00 



Rove Beetle (Dalotia (Atheta) coriaria):

100 Beetles (22712): $40.00 suited for areas up to 1,000 feet

1,000 Beetles in 1L tube (22713): $150.00 suited for areas 5,000 to 10,000 feet

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SMALL: $52.00 (22820)

Contains: 10,000 cucumeris

                  3,000 Hype-O

                  10 Sticky Cards

Combined value of $57.00

REGULAR: $96.00* (22822)

Contains: 1L tube cucumeris

                  1L tube Hype-O

                  10 Sticky cards

Combined value of $105.00

*Make it Deluxe (22825): add Nemasys for total of $155.00, combined value of $180.00

Pictured top: Both sizes of Hypoaspis (Stratiolaelaps) 3,000 (Hype-O) on the left, and the 1L tube behind.

Pictured middle: The lids of both the Stratiolaelaps (left) and cucumeris (right). Either of these mites can be stored for up to 5-7 days if kept in a cool room (12-20C) with the filter paper lid facing up, as pictured here.

Pictured bottom: The small vial (100 count) of the Rove Beetle and the large 1L tube (right).