Can patterned tapes significantly improve thrips catches?
You’ve likely noticed by now that thrips populations are especially high because of thehot, 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.
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.
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.
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!).
It’s an exciting time for Floriculture IPM! I am VERY pleased to announce the launch of the all newGreenhouseIPM website! GreenhouseIPM.org 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: (firstname.lastname@example.org 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 greenhouseipm.org.
GreenhouseIPM.org 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.
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 enemiesare 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.
Figure 1. Various fungi growing on a 3M Yeast and Mold Petrifilm
Distilled (sterile) water. Unopened bottled water will do in a pinch. Do NOT use tap water.
Figure 2. 0.2mL sterile, disposable pipettes that can be obtained from Amazon.ca.
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 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 testproduct that has beensitting 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.
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” isalsoimpossible 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, inthe 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).
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 Canadaas 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 mentionDelphastus 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 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.
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.
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 trialto 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.
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.
Long-tailed mealybug (older nymph or adult). Photo by S. Jandricic. Mealybugs produce unsightly, cottony masses, and produce large amounts of honeydew.
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 likeBeleaf 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 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 flowercrops, 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.
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 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: