I’ve written about the tropical pest Thrips parvispinus, now being called “pepper thrips”, infesting certain tropical ornamentals in Canada before. But it appears this pest has become widespread in Florida.
As Ontario sources much of its plant material from Florida, it’s a good idea to exercise caution, even on non-tropical plants. The known host range of this pest is evolving, and thrips have the potential to hitch-hike on less-preferred plant hosts and spread to more preferred hosts in your greenhouse.
Read on for information on the situation in Florida and what you can do to help protect your greenhouse from this pest.
What’s Happening in Florida:
Unfortunately for our friends in the south, T. parvispinus is no longer just a pest of greenhouse ornamentals but has permanently moved outdoors onto landscape plants. This makes it much more difficult to control, as it can constantly re-infest crops. (There is no worry of that in Ontario, as this tropical pest cannot overwinter outside here).
Along with ornamentals, it’s also been devastating pepper crops in Florida, another of its favourite hosts. Because of its high populations and significant threat to multiple horticultural crops, T. parvipinus is now a regulated pest in parts of Southern Florida.
As of March 31, 19 growers in Florida are under quarantine.
You can read more about the situation in this University of Florida Pest Alert and in this issue of Tech on Demand by Grower Talks.
Where do I find More Information About T. Parvipinus?
Given its broad host range, and that it has been found in several greenhouses growing tropical plants in Ontario over the last year, all growers (including those growing greenhouse peppers), should familiarize themselves with the following information:
- What T. parvispinus looks like
- It’s general biology
- Signs of damage
- How to scout for the pest
- Potential controls
- Who to send samples to for proper identification
Muchof this information can be found on the new website dedicated to Thrip parvispinus, run by researchers and extension agents at the Mid-Florida Research and Education Centre.
Thrips parvispinus is also included in the “Simple Thrips Key for Growers”, created by OMAFRA and the Vineland Research Innovation Centre. This easy-to-use picture key gives Canadian and Northern U.S. growers a tool to be able to distinguish T. parvispinus from other dark-coloured thrips (FYI, a microscope is needed). I’ve also done a previous post on what to look for and other thrips T. parvispinus can be confused with.
Additionally, The Horticultural Research Institute (HRI), in collaboration with AmericanHort, the Canadian Nursery & Landscape Association and the American Floral Endowment, is offering a free webinar on May 10 featuring three experts discussing Thrips parvispinus.
Topics covered on May 10th will include:
- History and Field Identification of Thrips parvispinus in Florida: Lance Osborne will discuss the response of USDA-ARS, University of Florida and Florida’s Regulatory Agency (FDACS-DPI) to the detection of this important pest. He will also discuss the use of observations and field guides to identify Thrips parvispinus.
- When, Where, and How to Monitor for T. parvispinus. Thrips parvispinus causes severe damage to several types of tropical ornamental plants. Sarah Jandricic will share what damage looks like on several plant species, where the thrips like to reside on the plant, and effective ways to monitor for them in your crop.
- Options to Manage T. parvispinus. Damage from Thrips parvispinus feeding reduces plant quality. Cristi Palmer will present outcomes from international efficacy research and options that are available in the US for thrips management.
You should register for this webinar immediately to stay on top of the latest developments.
Think you’ve found T. parvispinus in your crop in Canada? Adult thrips should be sent to myself (Dr. Sarah Jandricic, OMAFRA, Vineland station) for positive identification. Note that this thrips is NOT a quarantinable pest in Canada, so getting expert help and a positive ID can only help you in this case.
You can reach me at firstname.lastname@example.org or 905-687-1277.
Cutting Dips to Defend Against Thrips
Obviously, many of you reading this post are worried, as we get everything from tropicals and foliage plants, to chrysanthemum and gerbera cuttings from Florida. It really is the epienter of North America’s ornamental industry.
The good news (for us), is that cutting dips are registered against thrips pests in Canada. This technique uses reduced-risk pesticides such as oils, soaps and microbial insecticides to effectively smother thrips when they are briefly submerged in tubs of these products.
We know this effectively reduces western flower thrips arriving on potted mum cuttings when used properly and gives natural enemies time to build up on crops and work more effectively. This work on dips came out of the Biological Crop Protection Lab at the Vineland Research and Innovation Centre, headed by Dr. Rose Buitenhuis.
More recently, Rose and her Senior Lab Technician, Ashley Summerfield, have provided information on the efficacy of cutting dips on Thrips parvispinus. Similar to results with other thrips species, their work showed that dips in BotaniGard WP or mineral oil reduced Thrips parvispinus on plant cuttings by around 70%.
If you are interested in the full report from Vineland on dips for T. parvipsinus, including material and methods, you can Dr. Rose Buitenhuis at email@example.com.
How to I Best Use Dips for Thrips parvispinus?
We recommend that ALL growers begin implementing dips for both potted and garden mum cuttings coming in now, especially those coming from South Florida. (Note that oils are NOT recommended for garden mums due to phytotoxicity). One reason for this increased level of care is that chrysanthemums are technically on the host list for Thrips parvispinus. Although myself and other specialists across North American have not yet seen T. parvipinus cause damage on chrysanthemums, thrips coming in on this host have the potential to jump to other host plants in your greenhouse.
Studies from Vineland have also shown that soaps, BotaniGard WP and some oils can be used to combat thrips on more sensitive spring bedding crops.
Although most spring crops are already in the greenhouse, this is good to keep in mind for next year, as other known host plants for Thrips parvipinus include gerbera, impatiens, dahlia, gardenia, heliconia, roses and others. (As with mums, North American specialists have yet to see damage on these crops, but they remain a concern).
Label registrations have already been expanded to include cutting dips of spring bedding crops and other ornamentals (including tropicals) for certain reduced-risk products in Canada, including:
- BotaniGard WP: registered as a dip on all greenhouse ornamentals for whitefly
- Kopa soap: registered on all greenhouse ornamentals for whiteflies
- Landscape oil: registered on all greenhouse ornamental crops for thrips and whitefly
- Suffoil-X: registered on all greenhouse ornamentals for thrips and whitefly
To combat T. parvispinus on tropicals (the highest risk crop group), growers importing unrooted tropical plant cuttings should initially dip unrooted cuttings in Botanigard WP to control for whitefly (and incidentally, thrips) before sticking. Unrooted cuttings of tropical crops like mandevilla can be sensitive at this stage to oils.
Dips should be done regardless if T. parvipinus can be visibly seen on the cuttings or not, due to the highly damaging nature of this pest and the small size of the thrips and its larvae. This is true for plant material coming from Florida, as well as Guatemala and other warm locals, as this thrips now has a fairly broad host range!
BotaniGard sprays should be continued weekly on tropicals while in propagation, when humidity is high. OMAFRA and Vineland Research are hoping to investigate the usefulness of a second dipping of rooted cuttings of tropicals in 0.1% Landscape oil or Suffoil before potting, to further reduce thrips in production.
Much like a biologically-based IPM program in poinsettia for Bemisia whitefly (which can also come in on cuttings heavily treated with pesticides, and potentially be insecticide-resistant), the idea here is to use reduced-risk products in propagation, followed up with biological control several weeks later, to reduce your need to spray as long as possible.
By doing this, when you do need to spray for thrips later in the crop (e.g. when flowers develop), the pesticides we have registered here in Canada have a higher chance of working.
Although we are still working out which natural enemies work best, reports suggest Orius, green lacewings and A. swirskii all have the potential to help supress T. parvispinus populations.
What about Rooted Material Brought in For Finishing?
Although we have potential answers for greenhouse ornamental growers importing tropical cuttings and growing them through the whole crop cycle, the situation is more complicated for Ontario growers bringing up finished material from Florida. This is because Florida farmers are already spraying a large number of chemical pesticides (and often) to combat this pest. This means T. parvipinus coming in on plants could already be resistant to many active ingredients, and keeping them clean until sale could be a challenge.
Currently, we know the most susceptible host plants to T. parvispinus include the following:
Any of these plant species coming from Florida (or neighboring states) should be inspected thoroughly for T. parvispinus and its damage – damage is often the first sign of this pest, as the thrips itself is extremely tiny!
If evidence of T. parvispinus is found, you should immediately call OMAFRA or your pest management consultant for a positive ID.
It’s also a good idea to try to get the spray records from your supplier, if possible, so you can work with an IPM specialists to develop a management plan.
As for which pesticides and IPM tactics are working for “pepper thrips”, that will be addressed in detail in an upcoming post. This will be based on data from both Florida and on-farm work done by OMAFRA (as soon as I finish entering all the data!). Make sure you are subscribed to ONFloriculture.com to get the latest information.
Dr. Sarah Jandricic has been the Greenhouse Floriculture IPM Specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) since 2014. She has previously done floriculture IPM research in the US (at Cornell University and North Carolina State) and spent two years as Director of Research at a private IPM consulting company.