In Case you Missed it: UofF Webinar on Latest Thrips parvispinus Research

On March 12th, 2025, Dr. Alexandra Revynthi’s lab (University of Florida) gave an amazing update on what they’ve been working on with regards to Thrips parvispinus. A lot of this was important basic knowledge about their biology, such as development time and survival at high temperatures. There were also quite a few lab and small greenhouse trials looking at potential biocontrol agents.

Some of this will be information we build on to create effective IPM programs for Parvi in the future. But some of these findings, you could put into use right now.

You can go watch the full webinar using the link in the full blog post, or read my summary notes and see what I thought were the important take-aways.

Link to the Zoom Recording:

There is LOTS of good info this webinar, so don’t let the 2 hour run time scare you. You can watch the full using this link.

TLDR (Too long didn’t read – or watch, in this case):

If you don’t have time to watch the webinar in full at the moment, and just want the Cliffs notes, here’s the important points I took from the webinar. I’ve also included my thoughts about which information you could put into practice now, versus things we should take a “wait and see” approach on.

There was a lot covered in this webinar, so I’m including a table of contents in case you want to jump to a specific topic:

1. Link to the Zoom Recording:
2. Current Regulatory Status:
3. Basic Biology of T. parvispinus
4. Efficacy of Chemicals in the Greenhouse:
5. Curative vs. Preventative Sprays
6. Dipping URCs to Reduce Parvispinus:
7. Use of Microbial Pesticides:
8. Preliminary Results with Nematodes:
9. Preliminary Results with Large Biocontrol Agents:
10. Preliminary Results with Predatory Mites:
11. Take Home Message:

Current Regulatory Status:

From the webinar: Thrips parvispinus is no longer a regulated pest for nurseries in FL. Current quarantine orders will only target stock dealers with large thrips populations (not nurseries themselves).

Figure 1. High number of T. parvispinus females on a mandevilla flower. Photo by OMAFA.

What this means for you (the grower): The good news is that URCs may now have lower thrips numbers on them, if large Parvi populations are reported at a facility. We’ve already been seeing reductions since 2 of the main suppliers of mandevilla cuttings have screened their production facilities. BUT, finished products from FL nurseries may have high numbers of Parvi on them, as they are no longer regulated. So use discretion when ordering whole plants.

Basic Biology of T. parvispinus

Below are some things Alexandra’s lab learned about Parvi biology that I wanted to highlight. Make sure to watch the webinar for LOTS more good information.

From the webinar: Their development time (egg to adult) is fastest at 32 C (10 days), but takes much longer at lower temps., i.e. 31 days at 17 C. (See Figure 2, below).

What this means for you: This is useful to know in terms of resistance management , i.e. how many pesticide applications with the same IRAC group you can fit into the pest “window”, or generation time, of the insect. (See page 13 of this module on pesticide resistance for more info on this). You’ll have a much shorter pesticide application window at 32 C (e.g. 2 applications, 5 days apart, of the same chemical) than at colder temps (where you could do up to 3 applications, 7-10 days apart of a product, depending on the product label). Further applications of the same product (or same class of chemicals) outside this window could promote resistance to that class of chemicals.

Figure 2. Development time of Thrips parvispinus at different temperatures. Slide by Alexandra Revynthi.

From the webinar: The highest level of feeding damage is caused by adults in general, followed by L1 larvae.

What this means for you: This highlights the need for both adulticides and larvicides in our battle against Parvi. We’ve put together a Canadian pesticide rotation chart that addresses this, or you can check out the rotation program for Parvi put together by SePro for U.S. products.

From the webinar: Alexandra showed that adult Parvispinus could only survive for 24 hours with only water or pollen present (see Figure 3, below).

What this means for you: As soon as I saw this, all I could think of was CLEAN OUT YOUR GREENHOUSE BETWEEN CROPS. If you grow plants susceptible to Parvispinus in the North, it’s very important to leave the greenhouse compartment fallow before a new crop (even one that’s not preferred by Parvi) goes in. We are currently recommending 1 week between plantings here in Ontario. Make sure to sweep up ALL plant material immediately, and eliminate any weeds as well. It also wouldn’t hurt to wash out the greenhouse with a soap like Strip-It, followed by a sanitizer, like KleenGrow or Virkon, as you would for disease control. Keep the greenhouse compartment at a normal or higher temperature, to speed up the lifecycle of the thrips and make sure they die due to lack of food.

Figure 3. Data showing Thrips parvispinus can only survive for 24 hours in the lab without plant material. Data and slide by Dr. Alexandra Revynthi.

Efficacy of Chemicals in the Greenhouse:

From the webinar: Alexandra’s lab initially did their pesticide efficacy trials that lead to this paper in the lab. Their lab study on leaf discs showed that a product like Pylon (Piston in the U.S.), could give close to 100% control of Parvispinus. They repeated these trials on whole plants and found that, in a more realistic setting, Pylon only provided about 80% control of Parvi on mandevilla. Results were even worse with some of the other chemicals, e.g. Success/Conserve went from 80-100% control in the lab to just over 40% control on whole plants.

What this means: I don’t think anyone who’s been battling Parvi for the last 4 years was surprised by this, but it definitely helps us understand why this pest cannot be eradicated from greenhouses, even in the North, where there are no outside populations of Parvi invading. Simply put, we aren’t getting 100% control from any chemical we have.

Curative vs. Preventative Sprays

From the webinar: During their greenhouse trials, Alexandra’s lab also demonstrated some of the pesticides (e.g. Piston, XXpire, Timectin) had better efficacy when applied preventatively. For example, Pylon went from 80% efficacy when used curatively, to 90% efficacy when use prophylactically.

Figure 4. Comparison of chemical products when applied to mandevilla plants for T. parvispinus control, either curatively, or preventively. All data and graphs by Dr. Alexandra Revynthi.

What this means for you: I personally wouldn’t suggest putting on any of the products preventatively, except for perhaps biorationals like oils, given that there is not a big difference here (e.g. only a 10% gain when it comes to Pylon, and Success actually worked better curatively). Preventative sprays could also also increase the expense of a chemical program, as we are still likely to need curative sprays later in the crop. Further, preventative sprays run the risk of just heading us back towards calendar spraying (which can increase the chances of resistance), versus basing sprays on scouting and damage thresholds.

Dipping URCs to Reduce Parvispinus:

From the webinar: Similar to work done here in Ontario, Alexandra’s lab confirmed that oil dips can reduce thrips populations on cuttings (larvae) by 80-100%. What this means for you: Anyone growing tropical plants susceptible to Parvi from URCs should definitely be dipping their cuttings upon receipt. In Ontario, we are currently recommending Suffoil-X, as it can be less phytotoxic than other oils (which Alexandra also demonstrated). If you’re too worried about phyto, then BotaniGard WP is also effective. Studies are continuing at the Vineland Research and Innovation Centre to give a list of other products that are both effective and safe.

Figure 5. Work done by the Biocontrol Lab at the Vineland Research and Innovation Centre confirms that oils can effectively reduce incoming Parvispinus on plant material, similar to results prevented by Dr. Alexandra Revynthi (University of Florida). Slide and data courtesy of R. Buitenhuis, Vineland Research and Innovation Centre.

Use of Microbial Pesticides:

From the webinar: Alexandra’s lab tested a bunch of microbial pesticides, including ones we are familiar with (e.g. Beauveria-based products) and some ones we are less familiar with here in Canada (two strains of Isaria fumosorosea). Many of these had very good efficacy in lab tests. Of the WP formulations, the two Isaria products (Isarid and Ancora) worked best against all stages of Parvispinus, with the product Isarid resulting in 90-100% control in terms of both direct and residual activity, and Ancora around 85%. (You can find these results starting at about the 45 min point in the webinar recording). Of the liquid formations (OD or ES), Lalguard M52 worked the best (again, with near 100% mortality), with slightly more efficacy against larvae than adults (see slide below). It will be exciting to see what percent control they get with these products in greenhouse trials on whole plants, which are happening soon.

Figure 6. Relative efficacy of different microbial pesticides against Thrips parvispinus. Data and slide by Alexandra Revynthi.

What this means for you: Unfortunately, if you are reading this post in Canada, we don’t currently have any microbial pesticides containing Isaria fungi registered on any crop. This means it could be a few years before we get a product registered for greenhouse use. However, we do have Lalguard M52, and have been seeing good results with this product in commercial greenhouses growing Anthurium and Mandevilla. If you are in the United States, however, all 3 of the best microbial products are available to you: Isarid, Ancora and Lalguard M52. Any chemical program for Parvi should include these products as part of a rotation to improve control and decrease the chances of resistance developing.

Preliminary Results with Nematodes:

From the webinar: After confirming that T. parvispinus pupates in the soil (at a depth of about 1 inch) the Revynthi lab also tested different entomopathogenic nematode (EPN) species in the lab. Interestingly, our old friend S. feltiae was not different than water control. Other species of Steinernema worked better in the lab, and this was confirmed in greenhouse experiments. Applied at a rate of 100 IJ/cm2 to the soil of mandevilla plants, the best performers were S. carpocapse and S. riobrave (which is more generally used in turf). These provided a reduction in emerging thrips by about 60% compared to a water control.

Figure 7. Relative efficacy of different nematode species in controlling emerging T. parvispinus in whole-plant trials. Data by Dr. Alexandra Revynthi, University of Florida.

What this means for you: Given these results held up in whole-plant greenhouse experiments, I think it’s worth it to switch to S. carpocapse (which is commercially available in both countries), or at least a product that is a mix of S. feltiae and S. carpocapse, if you also want to control fungus gnats. I am uncertain if S. riobrave is available in Canada, so email me at sarah.jandricic@ontario.ca if you supply it!

Preliminary Results with Large Biocontrol Agents:

From the webinar: Several large biocontrol agents, including Orius, Macrolophus praeclarus (native to North America), Anystis, Dalotia coriaria and green lacewing, ate a LOT of Parvi in lab trials. Several of these biocontrol agents could also reproduce when fed a diet exclusively of Thrips parvispinus, which is also a good sign. Of all the biocontrol agents, Orius was probably the most promising in terms of it’s predation on all foliar-dwelling stages of Parvi, although Anystis definitely ate the most thrips!

Figure 8. Orius insidiosus searching for Parvispinus on a mandevilla leaf. Photo by J. Colley, Plant Products.

What this means for you: Although these results are very exciting, it’s too early to be implementing a complex biocontrol program involving these predators. This is partly based on the fact that we’ve seen VERY high pesticide residues on propagative material of both mandevilla and anthurium in the last year, which means bios don’t survive when used in propagation or at early production stages (where large bios would be most cost-effective to apply). Once the pesticide residues grow out, it may be more feasible to start adding Orius, Dalotia and perhaps Anystis to the crop as a means of suppressing Parvi. I suggest these, as they are the only natural enemies we’ve been able to recover after application in mandevilla in a collaborative trial with Biobee, OMAFA and an Ontario grower. A second trial by Plant Products in Ontario used Orius successfully in anthurium for control of Parvispinus, and for prevention in mandevilla (Figure 8).

Preliminary Results with Predatory Mites:

Webinar findings: In lab trials, all the of the predatory mites species tested preferred 1st instars of T. parvispinus – very few preyed on any 2nd instars (this part of the webinar starts around the 1 h 16 min point). Of the mites tested (including ALL commercially available mite species, plus some unique species found in Florida), the mites that ate the most Parvi larvae were Degenerans (5 L1 larvae/day) and Swirskii (4 L1 larvae/day). Stratiolaelaps scimitus is the only mite that could consume L2 larvae (besides Anystis, which I included in the “big bios” section), as well as pupae and pre-pupae in the soil.

Figure 9. Summary chart of commercial predatory mites and the life-stages of Parvispinus they are able to consume. Data from the Revynthi lab, University of Florida.

What this means for you: This data conflicts with Koppert’s recently published research that can be found in this magazine article, which showed that Limonicus seems to be the best predatory mite for Parvispinus. However, that’s neither here nor there, really, as both of these sets of data are from lab trials looking at mites and thrips in small cups – we need to wait for results to be in using whole plants. It will also be important to determine if mites can happily exist on the waxy surface of plants like mandevilla at all. In my trials with Biobee, we could not recover any predatory mites despite using sachets, blowing mites on weekly, and/or adding supplementary foods. The mites (both Cucumeris and Swirskii) just seemed to hate these plants. Similar observations have been made by Judy Colley at Plant Products in Ontario in anthuriums. I will be MORE than happy to eat my had if mites are shown to be effective in certain crops or using certain techniques at some point, but I’m not getting my fork and knife out just yet. It will also be interesting to see what rates of mites are needed per plant to keep damage levels acceptable, and if that’s at all economical.

Take Home Message:

I know I went over a LOT of material here, so here’s my take-home messages:

• There’s a lot of exciting work happening on Parvispinus and happening QUICKLY! With both Florida and Ontario leading the charge, as well as work being done in Europe, I think we might have some non-pesticide options to add to a chemical program soon.
• If I was a grower on a spray program, I would still be incorporating nematodes (S. carpocapse), microbials (Lalguard or Isarid) as well as some soil predators (Dalotia and Scimitus) into my program. These things can only help, and may help delay sprays of more expensive chemicals like Pylon or Success. S. carpocapsae may be especially helpful in propagation, where temperatures may be too high for the other natural enemies.
• I would DEFINTELY be dipping any incoming cuttings prone to Parvispinus in Suffoil or BotaniGard to reduce incoming thrips populations.
• You could try early, prophylactic sprays of products like oils in early production, to help suppress thrips once pesticide residues of cuttings have worn off (at around the 13 week point after cutting receipt, based on 2024 scouting data at a large commercial farm). This could help delay the need for chemical pesticides.
• I would wait on trying any foliar-dwelling biocontrol agents on a large scale at this point, until some whole-plant or greenhouse trials have come out on relevant plant species. But I’m hopeful these are coming soon and will be enlightening!