Several predatory insects and mites feed on thrips at different life stages, and using them together gives you the best shot at keeping thrips populations low. The most effective approach targets thrips both on plant foliage (where they feed) and in the soil (where they pupate), since no single beneficial bug covers the entire thrips life cycle.
Predatory Mites for Foliage
Two predatory mites dominate thrips biocontrol on leaves and stems: Amblyseius swirskii and Neoseiulus cucumeris. Both hunt thrips eggs and immature nymphs, which are the most vulnerable life stages and the ones worth targeting before thrips reach adulthood and start reproducing. Adults are harder for these small mites to take down, so early and preventive releases pay off more than reactive ones.
Neoseiulus cucumeris is the more widely used of the two and works best at temperatures between 75 and 85°F with relative humidity above 65% (ideally around 75%). It’s a reliable first choice in greenhouses and indoor grows where you can maintain those conditions. Many growers introduce it using slow-release sachets that hang on plants and dispense mites over several weeks.
Amblyseius swirskii performs best between 68 and 86°F with roughly 70% relative humidity. It handles warmer, more subtropical conditions better than cucumeris, making it a strong option for summer releases or warm growing environments. Both species can be released preventively before you even see thrips, as long as pollen or nectar is available for them to feed on in the meantime.
One important caveat: these two mites will prey on each other if released together. Pick one or the other for your foliar program rather than stacking both.
Soil Predators That Target Thrips Pupae
Thrips have an unusual life cycle. After feeding on leaves as nymphs, they drop to the soil to pupate before emerging as winged adults. This soil stage is a blind spot for foliar sprays and leaf-dwelling predators, which is exactly why soil-dwelling beneficial mites matter.
Stratiolaelaps scimitus (formerly sold as Hypoaspis miles) lives and hunts in the top half-inch of growing media. These fast-moving mites intercept thrips pupae and pre-pupae in the soil, catching them at a stage most other biocontrols miss entirely. They also feed on fungus gnat larvae and springtails, making them a useful all-around soil predator.
For preventive use, introduce about 10 mites per square foot of soil surface. If you already have a visible thrips or fungus gnat problem, bump that to 30 mites per square foot. Cannabis growers typically need to double even the curative rate because of the dense canopy and high pest pressure common in those environments. The mites ship in bottles or bags mixed with peat or vermiculite, and you simply sprinkle the material across the soil surface.
Green Lacewing Larvae
Green lacewing larvae (Chrysoperla carnea) are generalist predators with a big appetite. Unlike the adults, which feed on pollen and nectar, the larvae are aggressive hunters. They’re gray-brown, alligator-shaped, and equipped with large pincers they use to pierce soft-bodied insects and drain their fluids. They’ll eat thrips nymphs, aphids, mealybugs, caterpillars, and leafhoppers.
In lab studies, third-stage lacewing larvae killed between 40 and 90% of thrips they encountered, with the range depending on thrips density and conditions. That’s a wide spread, but it reflects the reality that lacewings work best as part of a broader program rather than a standalone fix. They’re especially useful when you’re dealing with multiple pests at once, since one lacewing larva handles several pest species without any additional cost or effort.
Lacewings are sold as eggs or larvae. Eggs are cheaper but take a few days to hatch, and some may be eaten by ants or other predators before they do. Releasing live larvae gets predation started immediately.
Why Combining Multiple Species Works
Thrips are difficult to control with a single predator because their life cycle spans two very different environments. Nymphs feed on leaves, then drop to the soil to pupate, then fly back up as adults to lay eggs. A foliar predatory mite like swirskii catches eggs and young nymphs on the plant. A soil mite like Stratiolaelaps intercepts the pupae below. Lacewing larvae add another layer of pressure on the foliage. Together, these beneficial bugs hit thrips at three different life stages in two different locations, leaving fewer survivors at each transition.
This layered approach matters because thrips reproduce quickly. A single female western flower thrips can produce dozens of offspring in her short life, so even a moderate number of adults escaping your biocontrol program can rebuild the population fast. Closing gaps in the life cycle is more effective than doubling down on just one predator.
Getting Conditions Right
Predatory mites are sensitive to temperature and humidity. If your growing space runs below 68°F or stays dry (under 50% relative humidity), mite populations won’t establish well, and you’ll burn through money on repeated releases that never take hold. Before investing in biocontrol, make sure your environment falls within workable ranges: 70 to 85°F and at least 65% humidity for most predatory mite species.
Soil predators are somewhat more forgiving since the growing media retains moisture, but they still need consistently moist (not waterlogged) substrate to thrive. If you’re growing in a very dry medium or using fabric pots that dry out quickly at the edges, Stratiolaelaps populations may concentrate only in the wettest zones and leave gaps in coverage.
Timing also matters. Releasing predators preventively, before thrips numbers explode, is far more effective than trying to catch up with an established infestation. Once thrips are visibly damaging leaves and you’re seeing adults flying around, biocontrol alone may not bring populations down fast enough. At that point, a compatible knockdown treatment followed by predator releases gives you the best combination of immediate relief and lasting control.