Tis’ the season to reflect on your Poinsettia strategy

In celebration of National Poinsettia Day, learn how to use BCA's to strengthen your future growth of this festive flower

Tis’ the season to reflect on your Poinsettia strategy

Happy National Poinsettia Day! Yes, you did just read that correctly — the 12th of December is the day growers, gardeners and even customers pay tribute to the exotic flower which for many has become the festive flower that beautifully encapsulates the essence of Christmas. Seeing as the native Mexican flower has a whole day dedicated to it’s existence and the man who made it a global festive phenomenon, Joel Roberts Poinsettia, we thought we’d mark the celebration by reflecting on this year’s Poinsettia growing season.

How did your poinsettias bloom this year? Did you use BCAs to their full potential, or maybe you didn’t use them at all? We sat down with our Technical Lead & Commercial Manager at Bioline Inc in North America, Ronald Valentin, to discuss the best ways for growers to maximise their poinsettia growth in the New Year.


“The meaning of ‘clean’ has two sides. Obviously, it’s expected that cuttings aren’t coming in from producers with unacceptable levels of pest problems—in this case, whitefly. However, trying to reach for ‘zero’ tolerance has probably also increased the development of resistance, as traditional pesticides are used exclusively and extensively.

The other side is that certain groups of pesticides can have very long residual effects on BCAs. For example, the A.I. acephate can have long residual effects on the wasps that are used for whitefly control (>8 weeks). So if this product has been used on the stock plants producing the cuttings, it wouldn’t work in favor of starting early with BCAs. If the whitefly on these same stock plants is resistant to this same A.I. (which ‘Q’ type Bemisia most likely would be), you end up with double the trouble — bad residues, but still having possibly unacceptable levels of whitefly on the cuttings.”


“Communication with producers and suppliers of cuttings is highly recommended to let them know your intentions of using BCAs. Many of the cutting producers have become much more active with producing BCA-ready cuttings, minimizing the use of “older style” chemistry and even using BCAs on the stock plant farms.”


“A technique that has picked up in recent years to help with a cleaner start with any young plant material has been dipping of unrooted or rooted cuttings into solutions to limit the level of whitefly being introduced. This has been supported with research in Canada that dipping cuttings into either an oil-based product (for example Suffoil X) or a solution with BotanigardWP will lower numbers of potential hitch hikers.

Often BotanigardWP is done in combination with nematodes (Steinernema feltiea) and RootShield to also target fungus gnats and fungal disease problems such as Pythium. Keep in mind that these products only work on contact with their target organism. So a whitefly adult or larva not getting in contact with spores of BotanigardWP will most definitely not get affected. Same with the oil products.”


“Nowadays, it’s very rare to see a poinsettia crop where the main whitefly species found isn’t Sweet PotatoWhitefly. This species can be in two bio types, named ‘B’ biotype and ‘Q’ biotype. The ‘B’ biotype is still relatively susceptible to traditional pesticides, whereas the ‘Q’ type is the one that has given some growers sleepless nights, especially when a population has been well established later in the crop.

Here’s the tricky part: you can’t tell the difference between the two biotypes unless you get them DNA tested. The other method for identifying which biotype you have isn’t recommended: the presence of ‘Q’ biotype is sometimes only discovered when certain traditional pesticides don’t seem to work as they “used to.” However, this typically means it’s too late and there’s a battle that’s already started.”


“The BCA that’s used for whitefly control in many different crops, including poinsettia, is Eretmocerus eremicus. This tiny wasp is completely yellow and is released as pupa into the crop using either blister packs (loose pupa in a small container) or little cards (pupa glued on the card). These blisters or cards are clipped on the side of the pot with the blister or card facing the pot. Releases should start as early as possible, as soon as mist starts for the cuttings or, for the growers receiving rooted cuttings, as soon as possible after transplanting (don’t forget to dip the liner).

Once hatched, these little wasps can fly and start their search for whitefly larva. They have two modes of action. The first one is host feeding, which is primarily done on younger larva. One wasp can kill 20 to 30 first instar larva per day. The second mode of action is parasitism of the older larva by depositing an egg underneath the whitefly larva, which in the end results in producing another wasp. Here’s the good news: these wasps do not discriminate between ‘B’ or ‘Q’ type and they’ll also control Greenhouse Whitefly as well.”


“In stock plant production, often Amblyseius swirskii is added as a third BCA, mostly in small-release sachets. This predatory mite feeds on whitefly eggs and is highly effective at high temperatures, consuming approximately 10 eggs per day, which is approximately 10% of what a whitefly female produces in her lifetime. On a higher-value crop, such as stock plants, it can be cost effective to use this predatory mite. Some growers also release these mites in the finishing crop, mostly as a broadcast application.

The timing of these applications is critical, at points where you have the highest leaf surface density, i.e. in plug trays JUST before transplanting and just before spacing in September. The reasoning is that these are predatory mites that don’t have the ability to fly, which makes it difficult for them to distribute throughout the crop. This is the advantage of the wasps—they can fly.”