Leafminer control in Ontario’s greenhouse crops -what’s working?

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Fig. 1. Leaf mines on gerbera leaves.

As much as we all hate thrips, there are, frankly, worse problems to have.  And it’s name is Leafminer.  These flies cause just about the ugliest damage we see in floriculture (Fig. 1), and they have incredible pesticide-resistance capabilities. Outbreaks seem to go in cycles, and I’ve had quite a few gerbera and mum crops come across my desk with leafminer this past 2 weeks.

This post covers chemical options (BawHawHawHa!!! Oh… Sorry… I’ll get myself under control now) and non-chemical options for leafminer, as well as how their control fits into the big picture in greenhouse IPM programs.  

Continue reading “Leafminer control in Ontario’s greenhouse crops -what’s working?”

Supplemental Lighting Options for Bedding Plant Seedling Production

Happy spring!  With the season in full swing, we know that growers are busy this month.  I read an interesting article on the effects of supplemental LED lighting in bedding plants this week, and I’ve summarized it here with the key messages at the bottom of this post.  It seems like an appropriate article for the season, especially if you are starting to think ahead to how you might improve production for the 2017 spring season.

Much of the LED lighting research done in ornamental plants has focused on finding the best wavelengths for plant production.  This can vary based on the plant being grown, and the qualities desired.  Before we dive into the study, let’s review some of the reasons why you might consider LED lights from a plant production standpoint. Continue reading “Supplemental Lighting Options for Bedding Plant Seedling Production”

A Burning Question: Ethylene and Sulfur Dioxide Damage in the Greenhouse

I’ve had a handful of calls in the past few weeks asking me to identify poor air quality damage on spring bedding crops.  Even if you have never had problems, the following is a good refresher on why proper maintenance of greenhouse heating systems is important.

 Natural gas and propane are popular choices when it comes to heating a greenhouse.  The products of burning fuel are carbon dioxide (CO2) and water (H20); both compounds we know are good for your plants.  However, combustion is often (if not always) incomplete, and impurities such as carbon monoxide (CO), sulfur dioxide (SO2) and ethylene (C2H4) are also released leading to poor air quality if your heater is not properly vented.

These impurities can leave your crop looking a bit down (Literally! It’s called epinasty, see more below), and it can happen in as little as 24 hoursContinue reading “A Burning Question: Ethylene and Sulfur Dioxide Damage in the Greenhouse”

Snack attack: how to help prevent your thrips bios from eating one another

Effective biocontrol programs for western flower thrips often use multiple natural enemies.  These include predatory mites like N. cucumeris or A. swirskii, but also  generalist predators like Atheta and Orius, which can feed on mite eggs and nymphs.

So, how can you make sure your generalist predators aren’t just eating all your predatory mites, instead of your thrips? Continue reading “Snack attack: how to help prevent your thrips bios from eating one another”

Managing Million Bells

By Sarah Jandricic and Chevonne Carlow

It’s that time of year again, when baskets of Million Bells (Calibrachoa) are going up in the greenhouse.  Here’s how to deal with and prevent some of their most common issues.

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Iron deficiency in Calibrachoa.  The resulting yellowing can look similar to symptoms caused by black root rot or nitrogen deficiency.

From a nutritional standpoint, the best thing you can is keep the pH of your calibrachoa in its ideal range; between 5.5 and 6.0.  A pH higher than this can inhibit nutrient uptake, especially micronutrients such as iron. 

 

Iron deficiency can be difficult to distinguish from other issues (like Black Root Rot – see below), but typically leads to yellowing of new growth.  Leaves may only show chlorosis between the veins, or it may be spread throughout the leaf.  This is different from nitrogen deficiency where yellowing occurs in the oldest leaves. If iron deficiency occurs, adding a chelated form of iron is best for uptake.

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 from black root rot.

Million bells are also highly susceptible to Black Root Rot (Thielaviopsis) – I’ve seen this take out a good chunk of a crop.  Symptoms include:

  • Stunting of foliage and roots
  • Plants in a tray will have uneven heights
  • black areas on roots
  • yellowing of leaves

Prevention is worth a pound of cure with this disease, as it is difficult to eradicate once established.  Important steps to take include:

  • Proper Sanitation. To avoid an issue with Black Root Rot year after year, immediately dispose of  diseased plants, limit water splashing, and sanitize benches, floors and used pots/plug trays.  Always physically wash surfaces  with a cleaner to remove organic matter, then follow up with a  disinfectant such as KleenGrow (ammonium chloride compound).
  • Consider prophylactic applications of fungicides on plug trays.  Products include Senator (thiophanate-methyl) or Medallion (fludioxonil). Preventative applications are an especially good idea if you’ve issues in the past. Adding bio-fungicides containing Trichoderma harzianum (e.g. Rootshield, Trianum) may also help
  • Lowering your pH. This disease is significantly inhibited by a lower pH – between 5.0 and 5.5.
  • Manage fungus gnats and shoreflies, since these insects can spread Black Root Rot between plants. Treatments include nematodes, Hypoaspsis mites , or applications of Dimiln (diflubenzuron) or Citation (cyromazine).

If already established, rotated applications of Senator and Medallion may limit Black Root Rot, but are unlikely to cure it.

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Aphids tend to be found on flowers and new growth of Calibrachoa.

Lastly, Million Bells are highly attractive to aphids.  With baskets hung up in the greenhouse, they can be “out of sight, out of mind”, but  regular monitoring is needed to prevent large aphid outbreaks.  Place sticky cards directly in baskets, and routinely check plant material for aphid cast skins and honeydew.

Once aphids are detected (and they will be!), applications of  Beleaf (flonicamid), Enstar (kinoprene) or Endeavor (pymetrozine) will usually take care of them.  However, be aware that all of these insecticides take around 4-5 days to start causing aphid death.

 

 

 

Guide to Weed Control in Ontario

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Publication 75 covers herbicides for outdoor ornamentals and non-crop areas outside the greenhouse.

Ontario’s latest Guide to Weed Control is now available as a free PDF from OMAFRA.  Chapter 16 covers weed control in outdoor ornamentals, and includes effectiveness ratings for registered products.  This publication may also be useful for cleaning up weeds outside the greenhouse.

Note that the only herbicides currently registered for use INSIDE the greenhouse are EcoClear and Munger.  Both are acetic acid-based products appropriate for the control of broadleaf and grass weeds.

A hardcopy of the guide (Publication 75) can be ordered from OMAFRA here for a nominal fee.