Encyrtus aurantii at the Botanical Garden? How did those insects make their way into the Begoniaceae and Gesneriads greenhouse last July? At this point, the mystery remains unsolved, but one thing’s for certain, this was the first observation of the species in Québec: a very special event for the Botanical Garden, which is hosting the astonishing migration!
On the trail of the Encyrtus
The Encyrtus aurantii – also known by the name Encyrtus lecaniorum – is a highly beneficial insect. It’s a parasite normally sold commercially for the control of scale insects, which infest a variety of plants, especially tropical plants. Measuring about 2 mm, the Encyrtus aurantii is brownish-orange in color, and at first sight may be mistaken for an ant. These wasps often go unnoticed. Their presence here was revealed by the unusual coloring of the scale insects that had begun to infest a luxuriant begonia: their dark color indicated that they’d been parasitized. What is a parasitized insect? It’s a pest in which a beneficial insect (a parasitoid) has laid an egg. The beneficial insect develops in it, which results in the death of the host.
Alerted, the Botanical Garden horticulturists spotted the parasitoids under the leaves of begonias in late July and captured a few specimens, which they sent to the phytoprotection diagnostic laboratory at Québec’s Ministry of Agriculture, Fisheries and Food for identification. The sample proved to be of great interest, and those examples of Encyrtus aurantii are now the voucher (or reference) specimens in the Collection d’insectes du Québec (CIQ).
Integrated pest management: the way forward
Ridding a plant of pests is no mean feat if we want to avoid the use of pesticides. Using beneficial insects is an interesting approach: it allows for effective solutions to problems, with no side effects for either humans or plants. Thanks to Encyrtus auantii, the parasitized begonias at the Botanical Garden were entirely cleansed of scale insects in less than a month! Why hadn’t these parasitoids been used before? Because there was less demand for them here than in other countries like France, Germany, Belgium or Spain, so they’re not certified in Québec and therefore not commercially available.
Our Encyrtus population hasn’t finished its work: three or four of them have been shipped to the fern greenhouse to take care of a localized scale-insect problem. Will they get the job done? They’re the center of attention these days, everyone hoping they’ll succeed, once again, in their remarkable clean-up work… To be continued!