Does Hypena opulenta prefer DSV grown in the sun or does it thrive better on shade-grown plants?

by Sharla Foster, MSc candidate, University of Ottawa and Agriculture & Agri-Food Canada

Dog-strangling vine (Vincetoxicum rossicum, DSV) has been plaguing Ontario and Quebec for decades. With few effective control strategies practical for use at large scales, the biocontrol agent Hypena opulenta, a leaf-feeding moth from the Ukraine, was approved for release at several sites in Canada. There is still a lot to learn about these two species and the factors that may affect their interactions and in turn H. opulenta’s effectiveness as a biocontrol agent.

I am interested in how the quality of DSV affects the development and survival of H. opulenta larvae. As part of my master’s research, I took advantage of the dense patches of DSV at one of the initial release sites for H. opulenta, the Fletcher Wildlife Garden.

Over the course of the last two months of summer, I raised H. opulenta larvae on leaves from sunny and shaded patches of DSV. The goal was to see if their performance changes as larvae hatch closer and closer to the end of summer and if this depends on whether their food (DSV) grew in sun or shade.

I’m hoping this information can be used to manage additional control efforts or timed releases of H. opulenta as there be times at which the moth is less effective as a control agent.

At this point, I’m waiting for more moths to emerge before starting to analyze the data, but preliminary observations indicate that the larvae fed leaves grown in the shade consistently started pupating first (but only by about a day), which meant they also emerged first. All moths emerged from pupa.

A couple of larvae in the shade treatment continued to grow in their fifth instar for an extra 2 weeks and never pupated. They were not parasitized or visibly affected; one of my colleagues saved them in ethanol so we could run an analysis on them.

Meanwhile, I saw delayed development in the first instar in a larva fed sun-grown leaves, but later stages were normal and it eventually emerged as an adult moth.

I’m also waiting for analysis of leaf chemistry and will keep you posted as the project continues.

Sharla Foster was based at Agriculture & Agri-Food Canada this summer as she conducted experiments at the FWG. Her thesis advisors at the University of Ottawa are Dr. Heather Kharouba and Dr. Tyler Smith.