Tag: floriculture IPM

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!).

Whitefly:

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.

Mealybug control in Ontario’s floriculture crops

Ontario has several pests for which floriculture IPM programs have yet to be perfected.  Mealybug (MB) is one, and its incidence seems to be on the rise.  This post outlines current control strategies, but more work needs to be done.

Two species are generally a problem: the cirtrus mealybug (Planococcus citri) and the long-tailed mealybug (Pseduococcus longispinus).

A single long-tailed mealybug on a leaf.
Long-tailed mealybug (older nymph or adult). Photo by S. Jandricic.  Mealybugs produce unsightly, cottony masses, and produce large amounts of honeydew.
Citrus mealybug
Citrus mealybug adult (white, segmented insect), nymphs (small, pinkish) and egg mass (cottony blob below adult). Photo by G. Murphy.

 

MB control on potted plants is difficult, but is achieved through a combination of pesticides and removal of highly infested plants.

Contact pesticides don’t work for MB because of their waxy coating, and systemic pesticides like Beleaf and Intercept aren’t registered for MB.  Systemic pesticides also won’t provide complete control, since MB commonly feeds on stems, where active ingredients are less available (see this article).

Citrus mealybug feeding on a flower stem.
Citrus mealybugs feeding on a flower stem. Photo by S. Jandricic

Repeated applications of Landscape oil (which smothers MB) are your best bet in potted plants, and can be applied foliarly or as a dip. Note that  EVERY plant variety should be tested for oil phytotoxicity before use.

But, how do you control MB in a crop that you can’t throw out, dip, or apply oils to?

For cut flower crops, the answer seems to be with Cyrptolaemus (a predatory beetle specialized for MB) and some patience.

I recently visited a grower that released high rates of Cryptolaemus larvae in a test area in week 15 to see if they could get ahead of their problem MB this Spring (300 larvae/m2/week for 3 weeks).  They also released adult beetles in two houses at a low rate (0.17/m2), with hopes it would establish 1.

An adult Cryptolaemus beetle. Also referred to as “mealybug destroyer”. Photo by S. Jandricic

Even at such high release rates, control was slow – only 5-15% during the first 3 weeks.  This is likely due Cryptolaemus’s lower development and predation rates at lower temperatures (avg. 18- 20ºC). But, on week 18, MB control increased to 30%.  And, the larvae that appeared in adult-release areas seemed more voracious than their packaged counterparts, cleaning up some plants completely. 

A larvae of Cryptolaemus that crawled up a stem to eat mealybug. Cryptolaemus larvae are similar in appearance to their prey, also producing a waxy covering.
This Cryptolaemus larva is covered in a waxy, filamentous coating, making it similar in appearance to its prey.  Photo by S. Jandricic

However, once Cryptolaemus introductions stopped for a few weeks, progress stalled.  Weekly introductions were started on week 23 (0.17 larvae/m2 AND 0.17 adults/m2). 2

Now (as of week 28), up to 95% control has been achieved in some areas. We’re hoping the predator will be able to clean up most of the crop by fall. I’ll keep you posted!

What can we learn from this trial? To control MB with Cryptolaemus, we need the following:

  •  Warm temperatures. Cyrptolaemus doesn’t function well below 21 ºC; releases probably shouldn’t begin until at least week 18. Other control measures need to be taken before this (we are still working on what, exactly, these should be).
  • Releases of larvae AND adults.  Both were useful here. Attacking all MB life stages, larvae were effective in hot spots, but couldn’t disperse far.  Adult Cryptolaemus only eat MB egg masses, but dispersed and produced new larvae throughout the crop. (Note that Cryptolaemus adults will not reproduce if only longtailed MB is present!)
  • Repeated releases. MB produce a crap load of babies (>350 per female!), so consistent predation is key. Cryptolaemus doesn’t appear to establish in the greenhouse, so repeated introductions are necessary.
  • Patience. Cryptolaemus takes time to build up populations and start doing its job – sometimes several weeks. Growers should monitor pest and predator levels closely during this time, but resist the urge to switch to pesticides.
1 Product supplied by Koppert; insect levels monitored weekly by P. Kelley. Progress of the experiment was also observed by the grower and S. Jandricic. Final release rates worked out to 2-3 larvae/m2 and 2-3 adults/m2; successful rates are likely to vary between crops and situations.

 

TSWV sysmptoms in mums

Sorry for the back-to-back posts, but I thought those of you growing chrysanthemums would be interested in this post from MSU on recognizing Tomato Spotted Wilt Virus symptoms in your crop.

To confirm the presence of TSWV, samples can be sent to Lab Services at the University of Guelph.

TSWV is vectored by thrips.  With temperatures between 25 and 28 C for the next 10 days, thrips reproduction will be rapid.  Control of thrips (and elimination of infected plant material) is necessary to reduce virus spread.

Thrips biological control can be achieved in floriculture greenhouses using the predatory mite Amblyseius swirskii and/or A. cucumeris in combination with the parasitic nematode S. felitiae and foliar applications of BotaniGard.  Registered chemicals for thrips in Ontario include:

  • Beleaf
  • BotaniGard
  • DDVP smoke
  • Dursban
  • Kontos
  • Malathion
  • Met 52
  • Pylon
  • Orthene
  • Success

Upcoming Container Trial Events

In case any of you have forgotten, the Sawaya Garden Trials are happening TOMORROW in Simcoe!  It should be a great day.

Also keep your calendars clear for the new Ontario Container Trial and Workshop, a free event to be held at the Vineland Research and Innovation Centre on Friday, August 21st (9am to 12pm).

Some of the containers currently growing on the Vineland Campus, all ready for the Container Trial and Workshop on Aug. 21.
Some of the containers currently growing on the Vineland Campus, all ready for the Ontario Container Trial and Workshop on Aug. 21.

Similar to the container trials run by OMAFRA/UofG in previous years, you’ll be able to see how 200 different varieties of ornamental plants stack up against each other — all were grown by Rodger Tschanz (UofG) under the same growing conditions.

This year we’ve also added some bonus material, including:

  • Presentations on  new floriculture research coming out of Cornell University, as well as Vineland’s research on floriculture opportunities in the Asian-Canadian community
  • Details on the best performers of 2015, and which ornamentals were most attractive to thrips
  • a FREE BBQ lunch
  • a tour of Vineland’s new greenhouse facility.

Register for the event by Aug. 17th by calling 1-877-424-1300. Presentations start at 9am.  A public open house to view the containers will begin at 1pm.

 

 

Figuring out Foxglove Aphid Control

The spring bedding crop season is over, so now’s the time to reflect on what worked, and what didn’t, for foxglove aphid control.  This way we can prepare for their re-appearance in the fall.

Foxglove aphid feeding on pansy. Note the two dark-green spots on the abdomen and the dark leg joints which are characteristic of this pest.
Foxglove aphid feeding on pansy. Note the characteristic dark-green blotches on the abdomen, and the dark joints of both the legs and antennae. Photo by S. Jandricic, OMAFRA.

To recap, foxglove aphid (Aulacorthum solani) is a “cool weather pest”. It prefers temperatures between 15-25 C, and can’t survive in the greenhouse in summer (1).  Unlike other aphid pests, foxglove aphid tends to feed in hidden locations – primarily the lowest leaves of plants – making it difficult to detect and treat.

 

And, unlike green peach and melon aphid, biological control of foxglove aphid is definitely a challenge.

Some growers and consultants have been trying both Aphidius ervi and Aphidius matricariae for foxglove aphid.  But, as demonstrated by the Buitenhuis Lab here at Vineland, foxglove aphid is a terrible host for A. matricariae, and this wasp will barely parasitize it (see graph). Further, using A. matricariae for foxglove aphid can actually end up spreading this pest, and it’s damage (2).  This is because the wasps simply pesters the aphids to the point where they drop of the plant and go find a quieter place to eat.  So it’s pretty clear that releasing A. matricariae is simply a waste of money and effort if you’ve got foxglove aphid.

Number of parasitized foxglove aphids by different Aphidius species. Wasps were offered 50 2nd instar aphids.
Parasitism rates of foxglove aphid by different Aphidius species. Wasps were offered 50-60 2nd instar aphids. Tests were done in small plastic containers.

But what about A. ervi? Although parasitism rates were high in the lab (73%), results were not as good in practice. Tested in the greenhouse,  A. ervi was able to offer about 50% control of foxglove aphid after 1 release.  Repeated releases may offer greater control, but this is still not reassuring when you’re talking about a pest where populations can explode quickly.

Why A. ervi does a great job of parasitizing foxglove aphid the lab, but not the greenhouse, is something we’re currently investigating.  But until we have an answer, it seems that pesticides may currently be the best option for control of foxglove aphid in floriculture IPM programs.  With the current limitations on neonicotinoids, growers will want to turn to Beleaf or Endeavor. (But, since these two chemicals have similar modes of action, and it usually takes several sprays of either to provide complete control, you may want to consider rotating these chemicals with Enstar II to prevent resistance).

If you’ve had infestations of foxglove aphid in your greenhouse, and have anything to say about it’s control, feel free to leave me a comment!

(1)  S.E. Jandricic, S.P. Wraight, K.C. Bennett, and J.P. Sanderson.  2010.  Developmental times and life table statistics for the aphid Aulacorthum solani (Hemiptera: Aphididae) at six constant temperatures, with recommendations on the application of temperature-dependent development models.  Environmental Entomology 39(5): 1631-1642.
(2) L. M. Henry, J.A. Bannerman, D.R. Gillespie2, and B.D. Roitberg.  2010. Predator identity and the nature and strength of food web interactions. Journal of Animal Ecology  doi: 10.1111/j.1365-2656.2010.01723.x.

Banishing Broad Mite – New post in Floriculture IPM Blog

I’ve been getting a lot of calls lately about Broad Mites (Polyphagotarsonemus latus) in crops like New Guinea impatiens, torenia, begonias, exacum, ipomea and gerbera.  Broad mite can also attack chrysanthemums, so it’s time to start thinking about  control of this pest as you’re sticking your new cuttings. Read on for tips on monitoring and control.

Continue reading “Banishing Broad Mite – New post in Floriculture IPM Blog” →

A Crime Against Callies: Floriculture IPM of Black Root Rot

Diagnosing a plant with vague symptoms like wilting, yellow and stunting is much like being a “plant detective”. First, you need to profile the “victim” — here,  Callibrachoa plugs.  Then, collect DNA evidence.  Finally, use knowledge and instinct to narrow down your “suspects”.  Only then can you come up with a plan to stop the assailant.

Yellowed plant growth (yellow circle) and dead plugs (orange circle) on a plug tray of Callibrachoa.
Yellowed plant growth (yellow circle) and dead plugs (orange circle) on a plug tray of Callibrachoa.
An unhealthy plug; few white roots are visible.
An unhealthy plug; few white roots are visible.

In this case, our DNA evidence (c/o UofG Lab Services) gave me 3 possible suspects: Pythium disotocum, Fusarium oxysporum and Thielaviopsis basicola.   But which of these was the real culprit?

P. disotocum is rarely documented as an aggressive pathogen in flowers, so we can eliminate that.  Similarly, Fusarium is often “around” at low levels without causing a problem.  But, T. basicola, better known as Black Root Rot, is a common problem in Callibrachoa, specifically.  Rotting roots are not always directly evident (even under a microscope), but severe discoloration of the foliage is a good clue, since this pathogen produces toxins that result in yellowing.  Left unchecked,  Black Root Rot causes severe stunting and plant death.

Luckily, there are treatments for Black Root Rot, and preventative measures that can be taken.

A fungus gnat (left) and shorefly (right) caught on a yellow sticky card. Both of these pests can transmit Black Root Rot and other pathogens.
A fungus gnat (left) and shorefly (right) caught on a yellow sticky card. Both of these pests can transmit Black Root Rot and other pathogens.
  • Drenches of Senator 70 WP (thiophanate-methyl) are the best option for dealing with an existing outbreak of Black Root Rot
  • Black Root Rot is often transmitted by fungus gnats and shoreflies.  Management of these insects is key to prevention.  They can be controlled with soil applications of nematodes, predatory mites (e.g. Hypoaspis), or insect growth regulars like Dimilin (diflubenzuron).  These products are compatible with biocontrol programs for other pests, like thrips and aphids.
  • A high soil pH encourages the growth of Black Root Rot.  pH should be kept below 5.6.
  • Bio-fungicides containing the beneficial organism Trichoderma harzianum (e.g Rootshield) can help protect plants from this Black Root Rot if applied at planting.

For additional information on Black Root Rot, check out http://plantclinic.cornell.edu/factsheets/blackrootrot.pdf

 

Welcome to the new ONfloriculture Blog! Floriculture IPM info and more…

A Blog for Ontario Greenhouse Floriculture Growers
Welcome to the very first posting for the new ONfloriculture blog! With regular contriubtions from OMAFRA Floriculture Specialists, the goal of this blog is to provide Ontario greenhouse floriculture growers with timely, technical information to grow the best crops they can.

I encourage you to sign up using the “Follow” feature to your right: this way, new posts magically appear in your inbox.  Alternatively, you can check back regularly for  new information and helpful resources.  The blog will cover such topics as new strides in floriculture IPM of both pests and diseases, new pesticide registrations, flower production, emerging pests, and industry events.

Looking for a Particular Topic?
See the Topic Word Cloud on the right side of the screen.  Topics build themselves as we post blogs.  By clicking on a particular topic (e.g. “Thrips”), you’ll be taken to all related posts.  The most posted-about topics will be in larger font.

Short on time?
Feel like you don’t have time to really read a whole blog post?  Hey, I know the feeling.  So, for all posts, I’ll be doing my best to bold the most important parts, in case you only have time to skim.

 

When “harassment” is a good thing in your greenhouse

Well, now that I’ve gotten your attention, let’s be clear that I’m talking about bugs, here, people.  Specifically, Western flower thrips and predatory mites such as N. cucumeris and A. swirskii.

L2 western flower thrips next to a predatory mite egg (left) and 2 adult mites (right).
Second instar (L2) western flower thrips next to a predatory mite egg (left) and 2 adult mites (right). Photo credit: Sarah Jandricic.

We all know that predatory mites only kill and eat the small, first larval stage of thrips (referred to as L1’s).  Larger life stages (i.e. L2’s and adult thrips) are simply too large for the mites to kill.

But, that doesn’t mean they don’t help control them.

Predatory mites will repeatedly attempt to kill L2 thrips – attacking them up to  40 times an hour (1). The L2 thrips are able to fend off these attacks by either running away, or “slapping” mites in the face with their abdomens.  You can watch the hilarity that ensues when mites attempt to attack too-large thrips larvae here.

But this “harassment” by mites takes it’s toll on thrips.  Because thrips spend more time fending off mites, they spend 30% less time feeding (2).  Over time, this translates to 40% less damage on plants with predatory mites, compared to no mites (2).  And, the presence of mites can reduce survival of L2 thrips by up to 78% (1), probably because eating less means the thrips lack the nutritional reserves to complete development.

And all of this is accomplished just through “intimidation” of thrips by mites – not through consumption.  Scientists term these “non-consumptive” effects, and we are just starting to learn the importance of these effects in biological control.  Research is now suggesting that non-consumptive effects like “harassment” may actually account for 50% of the pest control we see in greenhouses (3).

This makes sense with our thrips example.  Not only do mites reduce the feeding and survival of larval thrips, but ongoing research from Cornell University  shows that the presence of mites reduces the number of eggs laid by adult thrips, and shortens adult thrips lifespan (4).  Even the presence of predatory mite eggs on a plant has been shown to  “scare” L1 thrips into eating less, according to research from Austria (5).

And, it would make sense that the more mites you have, the higher the number of “scary” encounters thrips will have with them, improving control. 

So, lets give a hand to the hard working, harassing, predatory mite, who’s doing more than we ever thought in floriculture IPM.  Stay creepy, little guys. Stay creepy.

References: (1) Jandricic, S.E., Schmidt, D., Bryant, G., and Frank, S.P, NC State University. Unpublished data. (2) Jandricic, S.E. and Frank, S.P.  2014.  Too scared to eat: non-consumptive effects of predatory mites.  IOBC/wprs Bulletin 102: 111-115; (3) Preisser, E. L, Bolnick, D. I., & Benard, M. F. 2005: Scared to death? The effects of intimidation and consumption in predator-prey interactions. Ecology 86: 501-509. (4) Loughner, R., and Nyrop, J.  Cornell University. Unpublished data. (5) Walzer, A., & Schausberger, P. 2009: Non-consumptive effects of predator mites on thrips and its host plant. Oikos 118: 934-940.