In the Agatha Christie novel Nemesis, Miss Marple receives a posthumous request: she must investigate a crime. As befits the mistress of mysteries, an intricate narrative follows where the nefarious perpetrator is extremely tricky to pin down.
As a young fan of the BBC’s adaptation of the Miss Marple books in the late 1980s, starring the inimitable Joan Hickson (was a little old lady ever so quietly unrelenting?), the word ‘nemesis’ has stuck with me. The dictionary definition is ‘the inescapable agent of someone’s downfall’ and/or ‘a long-standing rival or arch-enemy’. For the latter explanation, the following example is given: ‘will Harry Potter finally defeat his nemesis, Voldemort?’
It was with all of this in mind that I’ve spent the past 18 months battling my own nemesis: the house fly.
Gardening outside is supposed to be the biggest challenge. There are so many factors beyond a gardener’s control including the soil type, adverse terrain, inclement weather, and, in my case at least, three cats who view any newly turned ground as a giant litter tray.
But who knew that the most formidable environment would be my own house?
A bit of background. I love house plants. I’ve loved them since the 1990s when, in my tiny London flat, I killed ivy, mint and a cactus in quick succession, all notoriously unkillable species. But, as you grow older, the ability to keep things alive improves. I became more adept at maintaining the health of multiple indoor flora, including spider plants, succulents, poinsettias, and peace lilies.
So far, so smug. House plants are now an integral part of my interior décor – and the bigger, the better. I share my space with all manner of big beauties, from the braided money tree and devil’s ivy to monstera deliciosa and the bird of paradise. Then, in 2021, disaster struck.
It began during a regular potting-on of my house plants. While I usually stock up on bog-standard peat-free bags from a major retailer, this time I’d bought compost from a variety of sellers. It was my first year sorting out the garden of my new house – I needed a lot of soil and compost. As long as it was peat-free, I wasn’t paying an awful lot of attention to the brand.
Within days of potting-on, I noticed small, black flies hovering near the plants and a handful on the windowpanes. This quickly escalated, with the nuisance flies fanning out around the house. Mostly they congregated near sources of daylight but, once evening drew in, I saw them on light fittings. And so it began.
A week later and the flies had colonized my house. They were on plant leaves, crawling over compost, flickering at windows and, at night, hovering around lamps. I drew up a battle plan. 
I began with a softly-softly approach. Surely these house plant critters, also known as sciarid flies, were only a temporary problem? I did my due diligence on the internet and discovered there was an easy fix: water my plants less and let them dry out between waterings.
Ha! If anything, this made things worse. I tried the next internet solution: nematodes. Of all the websites I scoured, this was the most popular option. The microorganisms feed on fly larvae, thus interrupting the life cycle. I bought the equivalent of thousands, followed the dilution instructions, and waited for a miracle. None came.
But what did come was the black flies. I’d go out for a couple of hours and return to find a new infestation (apparently one goddamn fly can lay 150 eggs at a time). I went back to the internet.
Try a zapper, the computer screen told me. I listened and bought the equivalent of one of those UV lights you see in a chip shop. The ‘zzzzzz’ sound of those frazzled flies gave me an enormous sense of wellbeing.
But the zapper wasn’t enough. Next I tried the Gardeners’ World website hoping for a flash of inspiration. Spread a gravel mulch over the compost, they said, and you will break the life cycle of the fungus gnat. That was folly. I bought more grit than you can shake a stick at and it had zero effect. The plants were still riddled with my nemesis.
On to fly paper. I tried lots of different types before settling on bright yellow sticky traps. I bought in bulk, spending stupid amounts of money waging war on my unwelcome house guest. These sticky shapes actually worked but were, ultimately, no match for flies with a lust for life – a handful always avoided the traps and continued to procreate.
In the end, I gave up, admitted defeat, and dumped all of my house plants outside. The flies had won. Voldemort had triumphed. After a while, I tentatively bought a couple of new plants. I scrutinise them on a daily basis with a dedication known only to serious sleuths. Oh, and I have a fly swatter in every room.
Words and images by Helen Nugent, Editor of Northern Soul
This article first appeared in Catena
