MSU Extension Floriculture & Greenhouse Crop Production

A “new” invasive thrips species is emerging as a significant threat to floriculture: pepper thrips (Thrips parvispinus), also known as Taiwanese flower thrips or tobacco thrips. We say new since this thrip species has been on the scene in the United States for a few years now. It was first detected in Florida in July 2020 and has since been intercepted on incoming plant material in at least seven other states. It has been found intermittently in Michigan greenhouses since 2023.  

Unlike the more common western flower thrips, this species has a distinct appearance. It has a dark head, a beige thorax, a black abdomen and yellow legs. Males and females of this species differ in appearance. To the unaided eye, females appear two-toned with a distinct partition between their dark-colored abdomen and light-brown head and thorax. This trait is very helpful for initial recognition in the greenhouse. Adult males are approximately half the size of females and appear uniformly yellow or light brown.  

This species is also one of the smallest known thrip species and is unlikely to be confused with other thrips, except for Hawaiian flower thrips, which are rarely found in the continental U.S. Originating in Thailand, pepper thrips have spread worldwide with the movement of plant material.  

How much of a problem will this be for Michigan? 

In Thailand, this pest has caused major crop losses in peppers, raising concerns about its potential impact on Michigan floriculture. Like western flower thrips, pepper thrips tend to feed on leaves, flowers and even fruit, however they have not been reported to transmit any viruses to date. Evidence also suggests they may outcompete other thrips species, further amplifying their threat. 

What makes T. parvispinus particularly important is the type of damage it causes. Like other thrips, it feeds by scraping open plant tissue and consuming the contents. However, the damage from this species can be especially severe, leading to pronounced deformation and extensive brown scarring on young foliage and new growth. Affected tissue often becomes brittle and puckered, with a roughened appearance that closely resembles damage caused by broad mites (Photo 1), particularly when flower and fruit distortion occur. In many cases, plants become stunted and misshapen—outcomes that are not only unsightly but can easily render crops unsalable. This damage is the primary driver behind efforts to better understand and manage this invasive pest. 

Life cycle and symptoms 

Understanding the life cycle of Thrips parvispinus is key to managing its impact in greenhouses. Under typical greenhouse conditions, this species completes its life cycle in 13 to 14 days, with two to three of those days spent beneath the soil surface as prepupa and pupa. This is slower than the more common western flower thrips (Frankliniella occidentalis), which is the predominant thrips species in Michigan greenhouses. 

Female T. parvispinus lay around 15 eggs, far fewer than western flower thrips. Eggs are typically deposited in the bract leaves, often leaving behind small, round brown spots on flowers as a telltale sign. After hatching, larvae go through two molts over the course of four to five days before reaching maturity. Pupation occurs in the soil at a depth of about 1 inch. 

Adult females live for approximately nine days, while males typically survive about six. Like most insects, their rate of development is temperature-dependent: cooler temperatures slow development, and current research suggests they cannot survive sustained temperatures below 50 degrees Fahrenheit. This makes it unlikely for T. parvispinus to overwinter outdoors in Michigan. 

Within the greenhouse, this pest tends to feed in the upper canopy, where tender new growth is most vulnerable to damage. This behavior, along with its small size and subtle signs of initial infestation, underscores the need for early detection and timely intervention. This pest has a broad host range but has been shown to cause serious damage to various tropical plants such as Mandevilla, Gardenia, Anthurium, Hoya, Schefflera, orchids and Ficus, along with some annual bedding plants such as Gerbera and Poinsettia (Photo 2). Additionally, it poses a risk to specialty crops, including peppers, citrus, eggplant and strawberries. Notably, some white-flowered varieties appear to be more susceptible to damage.  

Research efforts 

Alexandra Revynthi, PhD, at the University of Florida is leading a comprehensive research initiative to better understand Thrips parvispinus. Working in collaboration with government agencies and private industry partners, her team is focused on identifying the most effective strategies for managing this emerging pest. 

To guide effective management strategies, the research began with laboratory assays designed to identify the most promising tactics and products for controlling T. parvispinus. Once initial results were gathered, the team moved on to trials under simulated greenhouse conditions to account for the added complexity of real-world environments. Several studies evaluated the effectiveness of four different control approaches: conventional insecticides, biopesticides, dipping treatments and biological control agents. This research is still ongoing, with additional studies planned to refine and expand current findings. 

Current findings and management recommendations 

Chemical control 

As part of the management study, researchers evaluated the efficacy of both conventional insecticide and biopesticide spray applications against Thrips parvispinus. A total of 21 conventional products and 11 biopesticides were tested using both direct contact and prophylactic trials to assess residual activity. Results showed considerable variation in effectiveness across products—some performed well in direct contact, while others were more effective when applied preventatively. 

Among the conventional options, 12 products emerged as the most promising: 

*MoA = Mode of Action 

Some compounds, like Mainspring, impact thrips but do not kill them immediately. Mainspring, for example, impedes thrips ability to feed, resulting in death by dehydration or starvation after several days. It’s recommended that growers evaluate materials for efficacy in their crop at least seven days after treatment. Additionally, each product varies in its appropriate application site (greenhouse versus landscape) and crop, so be sure to read all label requirements. 

For biopesticides, M-Pede, sesame oil and Ultra-Fine oil showed the strongest results, with garlic and thyme oil also demonstrating potential. 

*MoA = Mode of Action 
**UNM = Non-specific mechanical and physical disruptors 
***UNE = Botanical essence with unknown or uncertain MoA 

Although most botanical oils (aside from sesame oil) did not cause high mortality in these early trials, several products still showed strong potential for managing Thrips parvispinus by reducing feeding damage. Garlic, sesame, and thyme oils, along with mineral oils like Suffoil-X and Ultra-Fine, and the insecticidal soap M-Pede, consistently limited visible crop injury. These results suggest that, even without high kill rates, some biopesticides can play a valuable role in integrated management strategies by minimizing damage and preserving plant quality. 

Microbial insecticides 

The Revynthi lab evaluated the potential of entomopathogenic fungi (microbial insecticides) against Thrips parvispinus through laboratory assays. While these tests were not conducted under greenhouse conditions and research is still ongoing, the initial results are promising. 

Four wettable powders (WPs) and four liquid formulations were tested. Among the wettable powders, Isarid, Ancora and Bioceres stood out in direct contact treatments for their strong efficacy. When evaluating residual activity, all four wettable powders—including Isarid, Ancora, BotaniGard WP and Bioceres—showed encouraging results. Interestingly, for wettable powders, the method of application (direct contact versus residual exposure) did not significantly affect thrips mortality. 

For the liquid formulations, Lalguard M52, Velifer and BotaniGard ES showed the most promise in direct contact tests. All four liquids, including Bioceres EC, also performed well in residual activity trials. Note that with liquid formulations, direct contact treatments generally resulted in higher mortality rates than residual exposure. These findings suggest that microbial insecticides could become a valuable component of an integrated T. parvispinus management program, pending further validation under greenhouse conditions. 

*MoA = Mode of Action 
**UNF = Fungal agents of unknown or uncertain MoA 

Beneficial nematodes 

Researchers also explored the use of entomopathogenic nematodes to target the prepupal and pupal stages of Thrips parvispinus. The study investigated six different nematode species and included both laboratory assays and trials under greenhouse conditions. In the lab, four species demonstrated significantly higher thrips mortality compared to untreated controls. Heterorhabditis bacteriophora was particularly effective, eliminating about 50% of the thrips. Steinernema carpocapsae, Heterorhabditis indica, and Steinernema riobrave also showed strong results. When tested under greenhouse conditions, the same four species continued to outperform the others. 

Among the six species, S. riobrave and S. carpocapsae showed the greatest potential for controlling T. parvispinus. To maximize effectiveness, Revynthi recommends using entomopathogenic nematodes as part of an integrated approach, ideally in combination with other biological control agents. 

Biological control agents 

Researchers have also been evaluating a variety of biological control agents against Thrips parvispinus through laboratory assays. These tests are still ongoing and have not yet been conducted under greenhouse conditions. 

Among the predatory insects, minute pirate bugs proved highly voracious, effectively preying on first and second instar larvae (L1 and L2) as well as adult thrips. Lacewings were particularly effective against L1 and L2 stages but were less successful against adults. Rove beetles, however, showed no significant impact on prepupal or pupal stages. 

The evaluation of predatory mites revealed several promising candidates. Amblyseius swirskii, Neoseiulus cucumeris, Amblyseius andersoni and Amblyseius degenerans all showed a strong preference for L1 larvae, with A. swirskii and A. degenerans also feeding on prepupae. Anystis baccarum (Crazee Mite) stood out for its ability to consume a wider range of life stages—including L2 larvae, prepupae and pupae—with an impressive average of 14 thrips consumed per day. 

In daily feeding trials, A. degenerans consumed the most thrips among the common predatory mites, averaging six larvae per day, followed by A. swirskii (four per day) and N. cucumeris and A. andersoni (three per day). Stratiolaelaps scimitus primarily targeted soil-dwelling stages and L2 larvae but was less effective on the first larval stage. 

When it came to reproduction, A. swirskii, N. cucumeris and A. degenerans each averaged about one egg laid per day, while A. andersoni and A. limonicus laid around 0.5 and 0.3 eggs per day, respectively. Anystis did not lay eggs during the study. 

Overall, most predatory mites showed a strong preference for L1 larvae, suggesting that early intervention will be crucial for biological control programs targeting T. parvispinus. 

Looking ahead 

Universities and government agencies are actively researching pepper thrips due to its potential impact on the horticulture industry. Cindy McKenzie, PhD, with the U.S. Department of Agriculture is conducting research at the University of Florida. Erich Schoeller, PhD, has some newly funded research initiatives at the University of Georgia and Sarah Jandricic, PhD, with the Ministry of Agriculture, Food and Rural Affairs has ongoing research projects with Thrips parvispinus in Canada. Federal and state agencies view pepper thrips as potentially more damaging than western flower thrips, prompting investigations into its overwintering capacity in outdoor fields across the U.S. as well. 

Additional resources 

While significant progress has been made in understanding Thrips parvispinus management, research is still ongoing. Some products may require longer evaluation periods than the initial trials allowed. Current findings highlight a range of promising options, including chemical controls, dipping treatments, microbial insecticides, nematodes and biological control agents. However, real-world conditions can add complexity, and management strategies should remain flexible and adaptive. The information shared here is intended to inform decisions and serve as a starting point for developing an integrated approach. 

For more details, visit the University of Florida Tropical Research and Education Center’s Thrips parvispinus webpage or contact a member of the Michigan State University Extension floriculture team. 

The information presented here is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.