Controlling whitefly in French Poinsettias

30/11/2020 - With Christmas less than one month away, Poinsettias are starting to leave French nurseries and appear in retail outlets - ready to bring some much-needed festive cheer to homes.   

Key pest

Whitefly is one of the key pests Poinsettias growers must contend with worldwide.  

French growers are increasingly turning to Swirskii-System to control the pest – starting applications immediately after first leaf thinning. Biobest advisor Paul Tremellat recommends making introductions every two weeks – releasing 100 swirskii per m2 along with Nutrimite™.  

“This highly nutritional food supplement helps accelerate and enhance the development of the predator population,” explains Paul. “Nutrimite™ is generally sprayed onto crops with a Makita plus Nutri-App. However, recently we tried a different approach in Poinsettia crops mixing it with the swirskii material in the bucket; interestingly, this system appeared to be as efficient.

Season-long strategy

“In south-eastern regions of France whitefly can prove quite challenging to control in Poinsettias.  We therefore recommend growers continue this strategy throughout the season - from August to the end of November.   

“We also recommend deploying Bug-Scan dry yellow sticky traps. The traps play a key role monitoring whitefly levels. If the pest population is already too well established to be controlled purely by the predatory mites, we advise a single application of our bioinsecticide Preferal® to knock numbers back.”

Meeting retailer expectations

In northwestern regions, Biobest advisor Vincent Berruet recommends switching to Swirskii-Breeding-System (individual sachets) six weeks before the crop leaves the nursery. “The carrier from the loose material can remain on the plants - this doesn’t always fit with garden centres’ expectations,” he explains.
“In this region of France our whitefly control strategy includes two weekly introductions of Eretmix-System – a combination of the black parasitic wasp Encarsia formosa and the lemon-yellow wasp Eretmocerus eremicus. This system works well where temperatures are fluctuating. Following this strategy, growers haven’t experienced any whitefly issues this year.

Aphids well controlled

“However, aphid pressure has been quite high in this region,” he says. “I’m pleased to report growers have got good results using Aphidius-System and Aphidoletes-System at curative rates.”

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