Battling Broad Mite in Spring Crops

Broad mite, Polyphagotarsonemus latus. Photo credit: USDA BARC

I’ve hearing a lot lately about Broad Mites (Polyphagotarsonemus latus) in spring crops, especially Reiger begonias and New Guinea impatiens. Other crops that are commonly affected include torenia, exacum, ipomea and gerbera.  

Broad mite are often difficult to detect and control. Read on for tips on monitoring and the latest management strategies for this pest.

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Upcoming Floriculture Pest Management Webinars

Here at OMAFRA, we’re always happy to promote work done by our colleagues in floriculture extension, including Michigan State University Extension!

The Fall edition of their popular Bug Bites! Webinar Series features talks on onion thrips and thrips identification (by yours truly), as well as talks on nematode application, biopesticide interactions with beneficals, and supplemental nutrition for bios! It’s jam packed! Keep reading for all the details.

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Last chance to register for FCO’s Research Conference!

screen-shot-2016-12-21-at-2-48-09-pm Flowers Canada Ontario is hosting a Research Conference on February 1st.

The conference will focus on best management practices (or BMPs) in the greenhouse, including those for water management, lighting, and pest control.

Keep reading for details on speakers and registration.

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“Sticking” it to high populations of thrips in greenhouse crops.

Can patterned tapes significantly improve thrips catches?

You’ve likely noticed by now that thrips populations are especially high because of the hot, dry summer. Many growers are noticing their usual biocontrol programs can’t keep up, and further defenses are needed this year.

The use of mass trapping strategies may be the key to getting an edge over thrips. This post discusses the latest research on mass trapping of thrips in ornamentals, including patterned sticky tapes and the use of pheromones.  

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“Bug Dorms” – an incredibly useful tool to help answer pest questions in your greenhouse

A basic “Bug Dorm” from Bioquip.

Today I want to share with you one of my favourite things of all time – the Bug Dorm.  Basically a mini, insect-proof tent, Bug Dorms are an amazingly useful tool for conducting quick-and-dirty experiments in your greenhouse.  By containing (or excluding) insects, they can help growers answer SPECIFIC pest questions in their SPECIFIC crop or operation, without needing to wait for researchers to find the answers.


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Can you safely mix nematodes and pesticides?

Entomopathogenic nematodes – used to control fungus gnats, shoreflies and thrips – are often a “gateway bio” into biocontrol use in greenhouses.  This is because not only are they effective and easy to use, but they’re generally compatible with insecticide use.   Readily applied with regular spray equipment or through drip lines, nematodes can even be tanked mixed with pesticides to save on labour costs.

In this post, I’ll share some of my research at NC State, looking at which commonly used pesticides in Canadian and U.S. greenhouses are safe to use with nematodes.

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IPM “Basics” Workshop on Feb 25th

Scouting plants for insect pests: an IPM basic!

Check out this flyer for details on my “Intro to IPM” workshop on Feb 25th.  The workshop will cover identification of common pests (insects AND diseases!), review of IPM basics, and optimizing IPM strategies in greenhouse floriculture crops.

This is a great workshop for new greenhouse employees, first year scouts, or as a refresher.

A more advanced workshop will be offered in the summer on integration of biocontrol and IPM for key pests (date and exact topic TBD, so check back!).

Got thrips? Check out this exciting new resource!

It’s an exciting time for Floriculture IPM!  I am VERY pleased to announce the launch of the all new GreenhouseIPM website! presents a compilation of up-to-date information on Integrated Pest Management (IPM) and biological control  in greenhouses.

And, as part of the website launch, we are holding a  FREE THRIPS WORKSHOP (with a free lunch!).  The workshop will cover all the components of thrips IPM and how they fit into a greenhouse production system.

Dates are Nov 23rd (8:30-1pm) OR Nov 30th (8:30-1pm) at Rittenhouse Hall.  Please RSVP Rose Buitenhuis: ( or 905-562-0320 x749).  SPACE IS LIMITED SO RESERVE YOUR SPOT NOW!

The most current information on thrips and whitefly IPM is now at your fingertips at provides detailed descriptions of pests, biocontrol agents  and detailed instructions on how best to use biocontrols within an IPM program.

Its initial format it focuses on two key pests – whiteflies and thrips – and their control. The site will evolve to encompass all common insect and mite pests, as well as diseases, in greenhouse crops.

New tool in floriculture IPM: testing your microbial products.

What’s the first thing you do with your shipments of predatory mites, parasitoids and predators when you receive them?  You probably check to see if these natural enemies are alive before you put them out in the crop.

Now Albert Grimm (Jeffries Greenhouses) and I have come up with a way to check if many of your microbial products are still viable, too.

We’re still in the process of testing these methods for all microbial products, so please consider this preliminary.  Right now, we know this works for Beauveria and Metarhizium-based products only (e.g. BotaniGard, BioCeres and Met52).  I’m hoping to put the methods up for more products in December.

Supplies Needed:

Figure 1. Various fungi growing on a 3M Yeast and Mold Petrifilm

  • 3M™ Petrifilm™ Yeast and Mold Count Plates. These are pre-loaded with media that grow a variety of fungi (Fig. 1).  They are about the size of one playing card, are relatively affordable ($113.97/50), and are easily stored (click here for more handling details).
  • Disposable plastic water cups that hold at least 200 ml
  • Rubbing Alcohol
  • Small measuring spoon, like the kind you use in baking (i.e. can measure 1/8th of a teaspoon)
  • Disposable plastic pipettes (Fig. 2). I bought 0.2ml ones from ($4.16 for 100).
    • Distilled (sterile) water.  Unopened bottled water will do in a pinch.  Do NOT use tap water.


0.2mL sterile, disposable pipettes that can be obtained from
Figure 2. 0.2mL sterile, disposable pipettes that can be obtained from

Step 1: Disinfect the water cup and the measuring spoon with rubbing alcohol.  Wipe dry with paper towels.
Step 2: In one plastic cup, add a small amount of sterile water (a few mL is fine). Keep for Step 4 to act as a control.
Step 3.   Take a second cup to mix up your product in.  Add 200 mL of sterile water.  Then add approx. 1/16th of a teaspoon (0.3ml) of product (Beauveria or Metarhizium). To measure, fill the smallest baking measuring spoon (1/8th of a teaspoon) about half way.  Stir well. This will give an approximate concentration of 1 g/L, which is similar to recommended rates of these products.
Step 4: Take a disposable pipette and fill with sterile water.  (Make sure to re-seal your bag of pipettes so they stay clean and sterile). Grab a single Petrifilm and peel back the thin, clear cover on top.  Carefully squeeze the pipette to form a line of water across the surface of the Petri film.
Step 5.  Repeat Step 4 on the same Petrifilm using your product in solution. You can use the same disposable pipette (since it only had sterile water in it previously).

Figure 3. Photo courtesy of Albert Grimm. A 3M Petri Film used to test the viability of Met52 and BotaniGard microbial pesticides. The blank water control indicates that all fungal spores came from the products, not from the water source (here, distilled water).
Figure 3. Photo courtesy of Albert Grimm. A 3M Petrifilm used to test the viability of Met52 and BotaniGard. The blank water control indicates that all fungi came from the products, not from the water source (here, distilled water).

  • Step 6.  Gently drop the plastic cover back over the Petrifilm. Write directly on the plastic cover with a sharpie to indicate the position of your “control” water line and your “product” water line (see Fig 3).  Store the film between 20-25 °C in a dark location.
  • Step 7: After a minimum of 16 h (the time it takes for Beauveria spores to germinate), check your Petrifilm.  The sterile water line should be blank.  The Beauveria and Metarhizium lines should be light blue -the film has a dye in it that reacts to fungi (Fig. 3).                                 Note that this dye reacts to ANY fungi or yeast.  Thus, you CANNOT use it to diagnose what fungus is growing.  This is why the sterile water control is so important – you want to be sure the reaction is from your microbial product, and not from random fungal spores in your water.

With the growers still tentative in their use of  microbial-based products, this viability test may give growers some piece of mind.  It will be particularly useful for product that’s been shipped in hot summer months, or in the dead of winter, as some products are sensitive to extreme temperatures.  It can also be used to test product that has been sitting in storage for long periods.

Note that this is a simple live/dead test.  These methods do not quantify how much of the product is still viable.  That’s something Dr. Anissa Poleatewich (Vineland) and I are working on, as we think it would be useful to know if your product is decreasing in efficacy over time.  So, stay tuned for more information as we perfect our methods.

Floriculture IPM Check-in: What’s working in Points?

It’s that time of year again, where the struggle against pests of poinsettias is real.  So I thought it was time for a summary of what’s working in the industry, and what’s not. (Beware!  This is a longer post than usual!).


It’s no surprise that the biggest pest issue in Points is still Bemisia whitefly.

Bemisia whitefly on poinsettia.

For those of you relying on pesticides as your tool of choice, it’s time to cross your fingers and hope you’ve mostly got the less-resistant “B” species of Bemisia (click here for background on “B” versus “Q” ).   Against “B”, you may see results with chemicals like Distance (pyriproxifen) and Kontos (spirotetremat).   Dyn0-Mite (pyridaben) will also provide rapid knockdown of adult whiteflies only, so it can be used for crop clean-up.

But if you happen to have mostly the “Q” (or Mediteranean) species, you are pretty much out of luck when it comes to pesticides, except, perhaps, for Dyno-Mite.  “Q” is generally thought to be resistant to all our registered products for whitefly. “Q” is also impossible to distinguish from “B” without genetic testing, so you won’t know you have it until your spray program fails.

Given this, biological control really is your best option for whitefly control, at least until mid-October.  Why? Because, in the absence of pesticide pressure, “B” will gradually displace “Q” over the growing season (population genetics, baby!).  This means that crop clean-up with chemicals near the end of the season will have a chance of working, as long as you don’t start it too early.

Bemisia whitefly (left) and greenhouse whitefly (right).
Bemisia whitefly (left) and greenhouse whitefly (right).

But even with biological control, the pest-control gods refuse to favour us. One of our best weapons against Bemisia – the parasitoid Eretmocerus mundus – is no longer available in Canada as of this year.  So, we’ll have to rely on the less-effective parasitoid Eretmocerus eremicus. You’ll also want to co-release Encarsia formosa, since these will control any greenhouse whitefly that come into the greenhouse.  Encarsia will also do a bit of parasitising and host-feeding on Bemisia.

Bemisia whitefly parasitized by Encarisa (top, blackened pupa), versus one that’s been parasitized by Eretmocerus (bottom, yellowish pupa).

With E. mundus gone, some growers are avoiding parasitoids altogether and trying Amblyseius swirskii and/or Amblydromalus limonicus.  Although these mites do eat whitefly eggs and crawlers, research at Vineland by Dr. Rose Buitenhuis has shown that A. swirskii are less effective for whitefly control than E. eremicus.  So, I wouldn’t rely on these guys alone.  But, they may have a place alongside other whitefly biocontrols, such as sprays of Beauveria bassiana.

I’d also be remiss if I didn’t mention Delphastus catalinae.  This predator seems REALLY effective for our friends on the West Coast.  However, we’ve historically had less luck with it in Ontario.  Given their compatibility with whitefly parasitoids (they don’t attack parasitized whitefly), their use within whitefly biocontrol programs may be worth re-visiting.  But they may not establish unless you’ve got a moderate whitefly population already, and they are very sensitive to pesticide residues.

Ultimately, the trick will be finding the right combination of natural enemies to replace the job of E. mundus.  This is why Graeme Murphy (you remember him???) and I are also looking at the potential for the generalist predator Dicyphus hesperus to aid in whitefly biocontrol programs.  I’ll keep you posted on our results.

Lewis Mite:

Lewis mites (Eotetranychus lewisi) . Photo courtesy of the University of Maryland.
Lewis mites (Eotetranychus lewisi) . Photo courtesy of the University of Maryland.

Lewis mite (a species of spider mite) can be a real problem in Poinsettia around mid-October, when populations have built up enough to start noticing damage.  Early detection is difficult, since the symptoms are rather subtle at first: faint speckling and chlorosis (click for a link to pictures).  If left unchecked, the upper foliage will turn brown and the mites will form unsightly webbing.

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

Given that they are difficult to detect, many growers are turning to preventative applications of miticides.  These include Avid (abamectin), Floramite (bifenazate), Vendex (fenbutatin oxide), Shuttle (spinosad) or Forbid (spiromesifen).  This is usually done at the cutting stage, however.  Control of Lewis mite with pesticides is more difficult now that the poinsettia canopy is filling in, since Floramite, Vendex and Shuttle are all contact miticides. Applications of more systemic miticides at this point (like Avid and Forbid) may interfere with your biocontrol program for whitefly, since they can be hard on parasitoids or predatory mites.  

If you haven’t already treated for Lewis mite, walk your crop a little more often and look for the characteristic stippling symptoms.  Look for mites on the underside of these leaves. Lewis mite is often confined to a particular cultivar or spot on the bench, so consider throwing out infested plants, or simply do a spot spray of miticides. If you need to spray more than once, remember to rotate chemicals to avoid resistance.

There are also some biological control options for this pest, one being the predatory midge Feltiellae.  But, at this time of year, the midge is starting to enter diapause, so it likely won’t be active enough to give you control in time. However, you might see some control with releases of the spider mite specialist Phytoseiulus persimilis.

Pythium root rot:

Now that the plants are off the misting bench, our focus turns from Erwinia to Pythium root rot.

Wilting on a bench of otherwise healthy plants suggests Pythium root rot.
Wilting on a bench of otherwise healthy plants suggests Pythium root rot.

Above-ground symptoms of Pythium include stunting and severe wilting.  There will also be evidence of dark, wet, rotted roots.  But if you’re not sure if Pythium is your problem, check out this Poinsettia Diagnostic Key from the awesome horticulturalists at NC State University.

Brown roots on a wilting plant is indicative of Pythium infection.
Brown roots on a wilting plant is indicative of Pythium infection.

The old standby chemicals for Pythium,  including Subdue (metalaxyl), Truban  (etridiazole) and Previcur (propamocarb hydrochloride), still usually work for Ontario growers – but this may not be true forever.  Many growers in the U.S. have been encountering fungicide-resistant Pythium strains, especially with regards to Subdue.  Because of this, many growers in California have starting applying microbial fungicides at the cutting stage to boost root growth and prophylactically help prevent disease — something to think about for next year.

Additionally, Dr. Anissa Poleatewich (Vineland) and I are running a commercial trial to see how drenches of microbial fungicides measure up to traditional chemicals for Pythium control over the season.  Keep your fingers crossed that we get some good data to share!

Whew!  That was a long one!  And I STILL probably didn’t cover everything!  Feel free to call or email to discuss issues not addressed in this post.  Commenting below on what’s working and what’s not for your particular operation is also encouraged.