When Thrips parvispinus first came on the scene in Ontario, our one goal was to knock back this pest any way we could. Four years later, we are suffering the effects of an all-chemical program. This includes high costs, along with insecticide resistance developing in two-spotted spider mite, which used to be managed biologically before Parvipsinus came along.

Based on OMAFA’s work with commercial farms, along with input from technical reps from biocontrol companies, we’ve come up with a more refined IPM program for Mandevilla that balances Parvispinus control while taking into consideration other pests, as well as costs.

I’ll be going over this program in detail over a 3 part series, so buckle up!

There’s going to be a lot of content in these posts, so I’m including a handy-dandy table of contents if you want to skip to a specific section:

Original Spray Program for Parvispinus

Thrips parvispinus was first found in Ontario in 2021 on mandevilla and dipladenia, and has since been found in a LOT of other ornamental crops.

The original rotation guide for Parvispinus (Table 1, below) was developed by Judy Colley at Plant Products and myself in early 2024. We wanted to give growers a full list of Canadian products with efficacy against Parvispinus, based on our field experience. It also was designed to help mitigate potential resistance development in Parvispinus via rotation of IRAC groups.

However, it wasn’t specifically designed for any particular crop, so it didn’t take into account things like other pests or crop longevity.

As two-spotted spider mite (TSSM) is MUCH more likely to develop resistance to chemicals than Thrips parvispinus, it’s now clear a more conservative use of pesticides is needed in longer-term crops that get TSSM, including mandevilla and hibiscus. This necessitates leaning more heavily on a few non-chemical approaches.

The original rotation program can still be used for shorter-term ornamentals that are prone to Parvi (e.g. anthuriums, hoya), or for crops that are not generally hosts of TSSM.

IPM Program for Parvi, Aphids and Mites in Mandevilla

New Plan in PDF Form

After working with several growers in Niagara who were struggling with TSSM in 2025 in their mandevilla, Sarah Stuive (Regional IPM Manager at Global Horticultural) helped me tweak the reduced-pesticide program for Parvispinus developed by OMAFA (presented in this GrowON webinar) to also take TSSM resistance issues into account.

I’ve included the program as a PDF, (Fig. 2., below), for easy printing and reference. In the rest of the blog post, I’ll outline this program step by step and the rational behind some choices.

(Does this look pretty? No. Am I a graphic designer? Also no).

Treating Cuttings at Receipt:

Since we’ve done survey work to confirm that Thrips parvispinus invades Canadian greenhouse via imported cutting material (Fig. 3.), treating your cuttings when they arrive is a critical step in the program, to significantly reduce starting populations.

As most of the Parvi come in on mandevilla as either eggs or lavae (only 7% came in as adults in our trials), these are the main life stages we need to treat. This can be achieved through two possible methods.

Cutting Dips

The Vineland Research and Innovation Centre has been hard at work adapting their cutting dip research, originally developed for Bemisia whitefly and western flower thrips, to look for the most effective products and procedures for Parvi. There’s been a special focus on which products can help kill thrips eggs embedded in the leaf tissue, as this is going to offer better control of this hard-to-manage pest.

There have been some really promising contenders. The main issue is that products that work well for one life stage of Parvispinus don’t necessarily work well for all stages. 

For example, all of the Beauveria bassiana products tested worked well for larvae, with the liquid formulations (BioCeres EC & BotaniGard ES) providing the best control (96-97% larval mortality). However, most Beauveria products didn’t give provide great egg mortality.

The product that worked best for eggs was Suffoil-X (reducing hatch by 66% when 5ml/L is used), but Suffoil-X only provided suppression of larvae (53% mortality). 

Unfortunately, the products that worked best for both eggs AND larvae don’t have cutting dips on the label in Canada yet (Bioceres EC and KleenGrow). Other products showed some phytotoxicity (e.g. M52), and should be avoided on propagation material.

Given all this information, the best option right now is Suffoil-X (at 5ml/L), which affects both Parvi eggs and larvae, along with BotaniGard WP, (2.5g/L) which doesn’t affect eggs, but gives a higher percent control of larvae (68%).  Suffoil-X, even at the high rate, did not cause any phytotoxicity in Vineland’s research greenhouse trials. Nor was phytotoxicity observed in a commercial farm trial at 2.5 ml/L. As a bonus, oils are known to have some effect on spider mite eggs.

Alternative Cutting Treatment: Chilling

Another option is to chill the cuttings to kill Parvispinus, given it is a tropical pest, and cannot overwinter in cool climates.

Trials from Vineland using walk-in coolers showed >88% mortality for eggs, larvae and adults when Mandevilla cuttings were held at 3 °C for 72h, with no ill effects on the cuttings. This was validated in on-farm trials by OMAFRA, where cuttings held at 3°C for 48h had similar rooting scores (see Fig. 5) as the control cuttings (immediately planted).

This will still need some individual on-farm testing to make sure your cooler level is stable, and doesn’t dip below 1°C for any extended period of time (the only time we saw cutting damage). But it’s worth trialing a batch or two when cuttings arrive in 2026, to see if you can make it work.

Vineland is continuing to play with temperature and time combinations, to hopefully get to 100% kill using this method. Wouldn’t that be amazing!!!

Treatments in Propagation

Biocontrol of Parvispinus

After dipping cuttings, you’ll have a brief respite where Parvispinus populations will be low. It doesn’t make sense to use pesticides here, especially given the limits on the number of uses per crop for the most effective chemicals for Parvispinus (e.g. 2 max. applications per crop for Kontos (spirotetramat), 3 for Pylon (chlorfenapyr) and Rimon (novaluron)). But it also doesn’t make sense to do NO control over the next 6-7 weeks.

Unfortunately, propagation of tropical crops during Ontario summers often reaches temperatures of >30 °C, meaning most biocontrol agents will likely be killed. This includes predatory mites, microbials, and any of the larger bios. Previous trials done by Biobee and OMAFA showed no recovery of any released beneficials over 7 weeks of propagation in 2024 trials.

The one control measure that DOES make sense is nematodes. Research from Florida, done at an average temperature of 27 °C, showed that the more warm-loving nematode species did better for Parvispinus control (Fig. 6). This includes either Heterorhabditis bacteriophora or Steinernema carpocapsae. (S. feltiae, a nematode that prefers cooler temperatures, didn’t even make it out of initial lab trials here). Nematodes are also somewhat shielded form the heat, being present in moist soil.

As the experiments in Florida were only 1 week long, at this point, we don’t know how frequently you’ll need to make applications for the best outcomes (while also balancing costs). Starting early in propagation and applying every other week is one strategy, and is less likely to oversaturate the media, which can lead to other issues. Alternatively, thrips numbers are likely to be higher later in propagation, so you could start week 3 and apply weekly.

Cleaning Up Plugs Before Potting

Despite dipping cuttings at receipt, growers have noticed that visible Parvispinus and their damage tend to resurge anywhere from 12- 16 weeks after initial sticking (or 5-11 weeks out of prop) (see Fig. 7). This is evidence that low numbers Parvi are still present after cutting dips, and are slowly building up over the 7 weeks of propagation. Actually monitoring the Parvi at this growth stage is difficult, due to the low numbers and the difficulty in tapping plug trays or using sticky cards under mist. But trust me, THEY’RE THERE. To ensure you’re potting the cleanest plugs possible, treatment at week 6 or 7 is strongly suggested.

Pesticide Applications

The best chemical option here is probably Kontos (spirotetramat). Kontos has shown excellent performance against Parvi in OMAFA’s on-farm trials in previous years. It works on larvae (likely the main life stage present at this crop stage) and has a relatively long residual. I’ve observed around 6 weeks of control of Kontos against Parvi, when applied as a drench.

Unfortunately, Kontos is simply too expensive to apply as a drench once plants are potted up, so applying at the end of propagation is a cost-effective use of this chemical.

The other benefit of using Kontos here is that it will help manage against the other 2 main pests of mandevilla: TSSM and Oleander aphid. It’s unclear whether these pests arrive on cutting material as well, or primarily enter from outside (or from other crops). Either way, I’m a big fan of using 1 chemical that provides protection against an entire pest-complex, versus using 3 separate chemicals.

If Kontos doesn’t float your boat, then check out the original Parvi spray guide at the top of this post for other options to use in propagation.

Dipping Liners

As drenching Kontos in prop will use up 1 of your 2 allowed applications per crop, you may want to use a different method to clean up plugs before potting, especially if you haven’t had too many issues with TSSM or Oleander aphid in the past.

Vineland has also tested dipping rooted liners (plugs) at the end of propagation. This “double dip” procedure was first suggested by my predecessor, Graeme Murphy, for better Bemisia whitefly control in poinsettia. In these tests, Suffoil-X came out as best choice in terms of safety on mandevilla, efficacy on eggs and larvae of Parvispinus, and being labelled for this use.

This second dip helps make sure your liners come out of propagation as clean as possible before they go into your production zone. The entire plug tray just getse dipped into the same 5 ml/L rate as for unrooted cuttings. In the Vineland trials, there were no negative effects on the roots or growing on.

Just a reminder to always check the use pattern of any product for dipping, to make sure if it can be used on both unrooted cuttings and/or plugs. You can check this on the greenhouse module Ontario Crop Protection Hub, where I’ve included information on dips/mist products in propagation.

Take Home Messages

Phew! That was a lot of information. But for now, you just need to download the PDF of the plan above, and remember these 3 main points when it comes to cuttings:

• Make sure to treat your cuttings going IN and OUT of propagation, to give you the cleanest plants at potting
• Use nematodes and dips of rooted liners to help preserve chemical applications for when you need them
• Make sure to use S. carpocapsae instead of S. feltiae for Parvi control

If you follow these recommendations, then this will set you on the right track going into production. Remember to stayed tuned for Parts 2 and 3, which will focus on spider mite resistance management and pesticide choices in production to reduce costs and the number of chemical applications.