This is the nematode you want as a soil-drench treatment for both fungus gnat larvae and thrips pupae. It can also be used as a foliar spray to control adult thrips if you’re able to keep your plants wet for an extended period of time.
This is our strategy for dealing with thrips. Each life stage has to be approached differently:
Adults can be trapped on yellow sticky cards and tape, or in shallow basins of water spiked with a few drops of soap and an aromatic scent (vanilla, peppermint, or almond work well) will attract and drown many. Use a shallow pan, filled with water and 1-2% of the scents, plus a couple of drops of soap to break the surface tension of the water and drown the pests.
Or, you could do something similar by dabbing cotton balls with the scents and sticking the cotton ball to the middle of the sticky card. This should attract the adult thrips, so that more will end up stuck to the cards. It’s also helpful to vary the height of the cards as you place them throughout your growing area. Hang some near the top of the plants, and others nearer to the pots.
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,The Nemasys comes in a pack that covers about 1000 – 1500 square feet. 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.
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.