Essential Facts About Thrips
Jan 27, 2025
What Does a Western Flower Thrips Look Like?
An adult Western Flower Thrips is about 1/25 of an inch long, making it nearly impossible to see any detail with the naked eye. Under magnification, however, you will see a slender, yellow or brown body with fringed wings. The various larval instar stages look slightly different, but as with most plant pests, magnification is crucial to be 100% sure of what you are dealing with. If possible, taking magnified photos or videos will greatly aid in our ability to assist with positive identification.
What Is the Lifespan of Thrips?
Given optimal conditions (approximately ~75 °F & low RH), Western Flower Thrips can hatch from their egg in 2-3 days, progressing through multiple larval instar stages. Once they reach adulthood, which can occur in as little as one week, each female can lay up to 80 eggs and can live for several weeks, laying hundreds of eggs during that time.
An Integrated Pest Management strategy can help keep the thrips under control while implementing effective practices to prevent the pest from appearing again.
Click here to check out a helpful video on Thrips: The life cycle of thrips
Where Do Thrips Come From?
Thrips are a cosmopolitan pest of many different plants, occurring in every temperate region around the world. There are several reasons why thrips might show up in your crop:
-Because they oviposit their eggs into plant tissue, they can easily be brought into a facility on propagated plant material without being identified through a visual inspection.
-Capable of flight, adult thrips are easily able to relocate and populate new areas, especially after being agitated by a neighbor's harvest of spray intervention.
-Thrips are often found in warm, dry conditions where plants become stressed. The plant's stress sends a signal to the thrips which acts as an 'invitation' to adult thrips who sense the plant's vulnerable state.
How Do I Know if I Have Thrips & How Do I Assess the Severity?
The damage caused by thrips appears as small silver or white streaks on the leaves, a result of the pest feeding on the plant through a chewing and sucking method. Black specks of excrement (frass) produced by adults and nymphs are also red flags to look for.
The most common thrips species in agricultural and horticultural facilities is the Western Flower Thrips (WFT), Frankliniella occidentalis. Populations of this pest can best be categorized in three levels: Low, Medium, and High, or 1, 2, and 3, respectively.
Level 1 thrips population indicates one or two adult or nymphal thrips on a leaf/flower with minimal damage/scarring observed.
Level 2 indicates populations of 15-20 on a leaf/flower, consisting of all life stages (egg, larvae, nymph, adult), and damage symptoms are more obvious to the naked eye.
Finally, level 3 indicates a significant level of all life stages, 25+ per leaf/flower, with easily visible damage throughout the crop."
How Do You Get Rid of Thrips?
Introduce predatory insects and entomopathogenic nematodes that are natural enemies of thrips, such as Orius insidiosus (minute pirate bug), Amblyseius cucmeris (Thripex), Amblyseius swirskii (Swirski-Mite), Stratiolaelaps scimitus (Entomite-M), and Steinernema feltiae (Entonem), at a rate commensurate with the population levels and appropriate for the crop type. The thrips lifecycle is complex and utilizing a combination of different predators and parasites to interupt theses different phases is highly recommended.
Orius insidiosus (Thripor) is a menacing thrips predator, known colloquially as the Thrips Assassin. Being capable of flight, this voracious predatory bug can easily travel throughout the growing area to hunt for and eliminate all above-ground phases of the thrips lifecycle. When introduced preventatively or at high enough rates, Thripor will work to significantly interrupt the various stages of the thrips lifecycle, thereby crashing both the pest's population as well as its own.
The predatory mites, Amblyseius swirskii (Swirski-Mite) and Amblyseius cucumeris (Thripex), are other options to specifically target the various larval instar stages of the thrips lifecycle that exist on the foliar areas of the crop. Although both of these predatory mites should not be introduced into the same crop at the same time, they each have their strengths and weaknesses in your thrips control strategy.
Thripex performs best in preventative situations, when the populations are nascent or very low. One limiting factor for Thripex is the temperature threshold of 86F, above which the Thripex become dormant. Thripex hanging sachets, and sachets on sticks, are fantastic options for early season introductions in areas known for annually recurring thrips presence. Early introduction can be the difference between a year-long uphill battle and a relatively easily controlled maintenance strategy.
Swirski-Mite is the more aggressive and impressive cousin to the Thripex mite. With their biological origins in the middle-east, Swirski-Mite can tolerate temperatures into the nineties without issue, making them ideally suited for warmer climates or mid-summer heat waves. Best utilized as a high-temperature or high-severity alternative to the Thripex, Swirski-Mite is a good choice in many instances for thrips control. However, as a Type III generalist, Swirski-Mite also has the ability to prevent or control existing populations of whiteflies, russet mites, and spider mites, and therefore might be a savvy choice for general preventative control when multiple pests are an issue.
The final stage of the thrips lifecycle that can be interrupted through biological intervention is the pupal phase. Pupating most commonly in the growing media/root zone directly underneath the foliage where they reside during their larval phases, thrips pupae are known hosts of the entomopathogenic nematode, Steinernema feltiae (Entonem), but are also readily fed upon by our soil mites (Entomite-M) and Rove beetles (Atheta). Choosing one, or multiple of these options will greatly aid in your efforts of minimizing the economic impact of thrips on your crop.
Essential for any strategy in controlling thrips, or any pest for that matter, designing and implementing a diligent scouting and monitoring program is perhaps the most crucial component of any successful IPM plan. Having an early-warning system in place will significantly reduce the number of beneficial insects inputted and therefore reduce the price-tag of a beneficial insect-focused IPM plan. Preventative measures beat curative reactions in every conceivable way.
Click here for some helpful videos on biological control of Thrips: Biological control of thrips - Neoseiulus cucumeris & Biological control of thrips - Orius laevigatus
Please reach out to our technical experts if you have any questions! We are happy to help you on your journey to a pest and pesticide-free cultivation strategy!
