Thrips have a very wide host range, damaging multiple plant varieties through stippling of the leaves which reduces photosynthesis, egg laying scars which causes deformed growth as the leaf or flower expands, as well as black fecal deposits on the leaves. They are also one of the primary vectors of plant viruses. This wide host range means that not only can thrips cause serious damage to most crop plants, they also pose a constant threat as majority of crops are surrounded by thrips pressure from nearby crops, lawns, trees etc.
(Thrips damage on Cannabis crop)
The primary thrips species found in Canada crops are Western Flower Thrips (Frankliniella occidentalis), Onion Thrips (Thrips tabaci) and European Flower Thrips (Frankliniella intonsa) all of which can be controlled by predatory mites. The primary two predator mites used in control of thrips are Swirski Mite (Amblyseius swirskii) and Thripex (Neoseiulus cucumeris) but how do you know which is the best thrips predator for your situation?
First of all, what are predator mites? Predator mites are tiny mites, typically just barely visible with the bare eye, that live on crop leaves and/or soil where they hunt crop pests. Some species act as a natural thrips control. The predatory mites sold commercially are typically fairly specific to pest, in this case let’s focus on Amblyseius swirskii and Neoseiulus cucumeris, which are both generalist predators (feed on other pests and also pollen and spores) with a long-proven track record as a thrips predator in Canada.
One of the most important things to keep in mind when using predatory mites for thrips control is that they primarily only feed on the first larval stage of thrips, which are tiny beige coloured larvae that hatch from the egg laying spots in the leaf or flower. This is key to understand as the later stages of the thrips life cycle need to be controlled by other means such as Thripor (Orius insidiosus) or Horiver sticky cards when thrips are being controlled curatively. Both of these predator mites lay their eggs on a specific type of plant hair (trichome) that are only present on some type of plants.
Both Amblyseius swirskii and Neoseiulus cucumeris are pretty similar at a quick glance; both eat roughly the same number of thrips larvae per day and have similar life cycles, where they differ is how quickly they can reproduce in your crop’s temperature range and under escalating pest pressure. For the majority of crops Swirski-Mite (Amblyseius swirskii) out performs Thripex (Neoseiulus cucumeris), as it does better under regular crop temperatures of 22C-35C (72F-95F) and responds quicker to increasing pest pressure by laying more eggs in the crop than cucumeris. Some crops (primarily ornamentals) are not conducive to predatory mite reproduction because they lack the type of plant hairs needed for the predator mite to deposit its eggs. In these situations, cucumeris may be a better choice as there is no value to Swirski’s higher level of reproduction and cucumeris has a lower cost per mite. It is also important to only place one of these predatory mites in your crop at a time, as swirskii and cucumeris are known to predate on each other at the expense of thrips control so mixing these products is not advised.
When looking into different types of Swirski or Thripex products, it is good to keep in mind that while sachets typically last 3-4 weeks, loose material needs to be re-applied weekly or bi-weekly. When choosing between products, you should be looking into your climate conditions and what type of crop you are growing. Sachets are often the best choice in crops like Cannabis or Houseplants because they are clean, easy to apply and provide the mites buffer against the low humidity climate (less than 50%) often found in indoor situations. Loose products are more commonly used in weekly curative ornamental treatments or as a quick boost in crops where sachets are already present.
Introducing predatory mites into your crop will provide you with long lasting natural thrips control and help decrease the possibility of a large infestation from developing. One application of our breeder sachets will give you up to four weeks of control, as the sachets release new predatory mites into your crop every single day. Predatory mites are often more effective than pesticide sprays, working actively against thrips larva and eggs you are unable to see, squeezing into small crevices pesticide sprays are unable to reach. Sprays also need to be applied multiple times for proper efficacy while predator mites maintain control for long periods. With pesticide sprays another issue can occur, pests often develop resistance to sprays, eventually becoming ineffective. Changing to biocontrol's is a more natural and safe way to remove unwanted pests from your crop.
More Information on Predatory Mites for Thrips Control in Canada:
Here is our general link to our Swirskii products: Amblyseius swirskii – Retail Koppert Canada
Here is our general link to our Thripex products: Neoseiulus cucumeris – Retail Koppert Canada