Turning the worm against pesky weevils

Research Lives: Dr Rosie Mangan, post-doctoral researcher, Department of Biology, Maynooth University

Dr Rosie Mangan: “As for insects, I find them fascinating. Love them or loathe them, you can’t deny they are vital for life on earth and they are the most diverse group in the animal kingdom.”

Dr Rosie Mangan: “As for insects, I find them fascinating. Love them or loathe them, you can’t deny they are vital for life on earth and they are the most diverse group in the animal kingdom.”

 

You work in the area of biological control – what does that mean?

My research looks at ways to protect plants from attacks by insects, but rather than using chemical pesticides, we are looking at introducing other animal species that naturally attack and control the pest, particularly in managed forests.

Why is it important to look for alternatives to pesticides?

Chemical pesticides can be very effective at killing off insects that attack forests and crops, but the downside is that the chemicals in them can persist in the environment, and they can be harmful to other living creatures, such as other insects and fish, birds, mammals and the humans who spray the pesticides. The EU-funded project I work on, BIOCOMES, looks at developing more sustainable and environmentally friendly alternatives to pesticides for agriculture, horticulture and forestry.

What pest are you looking to control?

My work focuses on the pine weevil, which is a small, beetle-like insect with a snout. It’s a huge forestry pest in Europe. Once the weevils arrive at a forest, they can quickly decimate newly-planted forests, completely wiping them out.

What alternative are you researching?

We are looking at using a type of tiny, microscopic roundworm to control the weevils. As part of their life cycle, the female weevils lay eggs in recently cut tree stumps, and when the eggs hatch the larvae come out and feed on the stump. These roundworms, which occur naturally in the soil, can get into the larvae and release bacteria from their guts. This effectively turns each insect larva into a soup so the roundworms can feed on it.

That sounds like something out of a horror movie! How effective are these roundworms at keeping the weevils in check?

We have done field trials with Coillte where we inundate weevil-infested tree stumps with the roundworms. When we do that we see about an 80 per cent reduction in the weevil infestation, which is highly effective.

Is it safe to introduce these roundworms en masse into a forest?

The beauty of these roundworms is that they need to feed on the weevils to survive, so when the weevil numbers drop, their numbers drop too. Also, they don’t tend to move far away from the tree stump where they have been introduced. So the relationship between pest and controller is quite contained.

How did you become interested in ecology and the environment and in insects in particular?

When I was in primary school my favourite part was nature walks, I just love the outdoors. Then when I was studying botany and zoology in University College Dublin I got the chance to work with the freshwater biology lab in the summers and it was so inspiring to be surrounded by lots of other students and researchers working on projects, getting a real feel for ecological research. As for insects, I find them fascinating. Love them or loathe them, you can’t deny they are vital for life on earth and they are the most diverse group in the animal kingdom.

What are the best and most challenging parts of your job?

One of the most fantastic things about working in ecology is that you go to places that are off the beaten track and it makes you appreciate how beautiful Ireland is, what a natural heritage we have.

The most challenging is that you have to be ready for things not to work and to be prepared to go back to the drawing board. But as long as you stick with it there is always something new to look at, to discover.