Lewis Mites 2025 – a Poinsettia Problem that’s Here to Stay?

*Lewis mite damage on poinsettia. Photo by OMAFA.*

Let’s face it: although Lewis mites (Eotetranychus lewisi) used to be more of a cyclical pest, this mite has been consistently bad in poinsettia the last few years. As regular Lewis mite infestations now seem to be the new normal in poinsettia, this week is the time to to start thinking about your pest control plan for Lewis mite.

Whether you choose the preventive route or the wait-and-see approach, knowing which strategies and chemicals are working is critical. Read on for tips on dipping to prevent mites along and what we learned from last year‘s chemical approaches.

Lewis Mite Symptoms and Scouting:

Lewis mite is closely related to spider mites (Tetranychus urticae) but are an entirely different species. If you need a refresher on symptoms or their biology, check out these posts:

Taking your Lewis mites for a Dip?

As we don’t see Lewis mites in other crops (except, perhaps, greenhouse strawberry) in Ontario, our Lewis mite problems are most likely coming from the producers, i.e. your cuttings. Research from the Vineland Research and Innovation Centre has shown that cutting dips can be highly effective for two-spotted spider mite as well as pests like Bemisia whitefly and thrips that arrive on propagative material. Given spider mites and Lewis mites are related, it stands to reason that dips might do Lewis mites good as well!

Traditionally we have used cutting dips that are a combination of soap and BotaniGard for Bemisia whitefly control in poinsettia. This is because it is highly effective, and also the safest choice in terms of phytotoxicity for growers who are concerned about that. Unfortunately, soap and BotaniGard seem to have little effect on spider mites.

However, the research also showed (see Table 1, below), that a low dip rate of 0.1% Suffoil-X was effective for Bemisia AND spider mites, reducing both by up to 75%, with little risk of phytotoxicity. If you’re struggling with Lewis mites regularly, then experimenting with changing up your dips on part of your crop this year is probably worth your while.

Table 1. Efficacy of various reduced-risk products when used as cutting dips against various pests. Chart courtesy of R. Buitenhuis (Vineland Research and Innovation Centre). Green boxes indicate high efficacy of treatments against specified pests. Caution symbols containing plants indicate a significant risk of phytotoxicity.

Treatment in Propagation / Early Production:

*Webbing caused by a severe infestation of Lewis mite. Photo courtesy of Ohio State University.*

Given that Lewis mites are difficult to detect, but end up causing a lot of damage, the easiest solution is often a single, preventative application of a miticide at the cutting stage.

Unfortunately, products traditionally used for Lewis mite don’t seem to be working as well the last few years e.g. Floramite (bifenzate). So what other options are there?

Avid (abamectin; IRAC 6), although hard on biocontrol agents, is currently our most effective chemical. It can be used effectively without derailing your bio program if you use it early in propagation as a preventative spray, before natural enemies are released. The residues generally dissipate before parasitic wasps are put on at potting. (This strategy obviously will not work if you release bios in propagation). If you’re hesitant to use Avid for compatibility reasons, then FujiMite is the next best chemical for Lewis mites and is a little softer.

Other products that can be used early in the crop (before bract formation) are listed here, but their efficacy may vary, as does their compatibility with biocontrol agents.

Table 2. Products for controlling Lewis mite early in production (before bract formation). Products with low efficacy are omitted. Efficacy data based on grower experience in Ontario, 2023-2024.

Product	A.I.	Application Type	Activity	Efficacy	Hard on bios?	CAN or U.S.?
Suffoil-X	mineral oil	Cutting Dip	Contact	***	n/a	Both
Suffoil-X	Mineral oil	Spray	Contact	**	Hard but short residual	Both
Avid	Abamectin	Spray	Translaminar	****	Hard -use in prop only – 2 wk residual	Both
FujiMite	Fenpyroximate	Spray	Contact	***	Moderate	Both
Vendex	fenbutanin oxide	Spray	Contact	**	Soft	Both
Kontos	spirotetramat	Spray or Drench	Systemic	***	Hard – drench only in prop	Both

Treatment in Late Production:

Controlling Lewis mite later in the crop can be tricky, given that some products are not safe on poinsettia bracts, and can also be hard on parasitic wasps that form the backbone of Bemisia whitefly biocontrol. However, Lewis mite are a relatively slow-moving pest, so you don’t need to blanket the whole bench or compartment. Spot sprays mean you could use harder products like Avid or Kontos and keep effects on natural enemies to a minimum.

If you want to focus on products that are safer for natural enemies, some growers have found Floramite still has some efficacy if followed immediately by Shuttle (acequinocyl). This combination remains fairly soft on parasitoids. Be aware that Floramite and Shuttle are in a similar chemical class (IRAC 20B vs 20D). Therefore, they should be used in the SAME pest generation “window” (2 week period), as opposed to alternating sprays over the season, as this could promote resistance.

Table 3. Products for controlling Lewis mite early late production (after bract formation). Products with low efficacy are omitted. All products are safe on bracts. Efficacy data based on grower experience in Ontario, 2023-2024.

Product	A.I.	Application Type	Activity	Efficacy	Hard on bios?	CAN or U.S.?
Avid	Abamectin	Spray	Translaminar	****	Hard -spot spray only	Both
FujiMite	Fenpyroximate	Spray	Contact	***	Moderate	Both
Floramite followed by Shuttle	Bifenzate, Acequinocyl	Spray	Contact	**	Soft	both
Kontos	Spirotetramat	Spray or Drench	Systemic	** (not as good for clean up)	Hard – spot spray only or drench	both
Magister	Fenazaquin	Spray	Contact	**	Hard on mites, moderate on parasitoids	both

*Miticides chosen before Sept 29 should be soft on natural enemies such as Encarsia, as to not interfere with biocontrol of Bemisia whitefly. Photo by OMAFA.*

If you find yourself needing to do a second spray 2 weeks after the first spray, then Vendex (fenbutatin oxide; IRAC 12) may be a good option, and is also soft on bios. However, it is NOT safe for use at the pre-bract stage and beyond. Magister (which has no label warnings about bracts) provided about 50% kill of Lewis mites in grower trials last year, so Magister is a potential option to include in a rotation program where biocontrol is a consideration.

Spear T (IRAC 32) is also a relatively new product on the market, derived from spider venom, and is reportedly effective on both two-spotted spider mite and whitefly, and therefore may be useful in poinsettia production. However, close observation would be needed to determine it’s efficacy on both Lewis mite and Bemisia whitefly, as well as it’s effects on parasitic wasps.

As the season progresses, control with contact insecticides like FujiMite, Floramite, Shuttle and Magister will be much more difficult since the canopy is denser. Translaminar or systemic miticides will be more effective for Lewis mite at this time (e.g. Avid, Kontos), but will likely interfere with whitefly biocontrol programs. However, if you’re on a chemical program for Bemisia whitefly (or need to switch to one if whitefly pressure is high), late September or early October this is the perfect time to apply Kontos, as it will also help control whitefly nymphs (see diagram below).

What about Biocontrol/Cultural Controls for Lewis Mite?

If you are a facility that is focused on getting to sale using only biocontrol in Poinsettia, then your best options for Lewis mite control are Amblyseius fallacis and Neoseiulus californicus (with Californicus generally being the cheaper, and therefore preferred, choice). Note, for this to be effective, you have to put these out early and at high rates (at least 5/sq ft). Both of these predators can eat other sources of food besides prey mites to survive (e.g. pollen) and are tolerant to the high temperatures poinsettia are produced under.

If put in the crop early (i.e. in propagation or immediately after potting), then predatory mites can help keep Lewis mite in check – but spot sprays may still be needed in a warm fall. According to a hot tip from Ecohabitat at 2023’s Poinsettia Open House at Sawaya Gardens, A. fallacis also seem more tolerant to Avid residues that other bios, and could be released 3-7 days after spot sprays of Avid as extra insurance.

As for cultural controls, a hot tip from a big grower is to take the old leaves off the poinsettia plants. This should happen about 2 weeks after pinch, when all the new side shoots are breaking. This can really help reduce the Lewis mites by removing the original infestation at the source, before they have time to travel to the new growth. And you don’t have to remove the leaves entirely – just slicing the petiole will cause the old leaves to dry up and the Lewis mite colonies to fall to the soil and die.

Special thanks to the consultants and IPM staff that keep me (and you!) in the loop for the content of this post!

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