The Long Gallery, Library at Blickling Hall (Photo Martin Pettitt from Bury St Edmunds, UK, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)
Dear Readers, clothes moths are the bane of many a household. Here in Bug Woman Towers, they have munched through suits, demolished my one and only cashmere jumper (charity shop, naturally), eaten woollen rugs and had a field day with some of the antsy-fancy woollen blankets that I make. Imagine, then, the problems in a stately home, full of tapestries and carpets and clothing and all sorts of other clothes-moth fodder. Whilst in a domestic house, a pest controller might come in and fumigate the whole place (not that this is great for humans, pets or indeed the other creatures that might share your house), this is often not an option in a heritage property, where chemicals might damage fabric.
So, I was intrigued to read today that Rentokil was planning to use a tiny parasitic wasp (Trichogramma evanescens) as a way of controlling clothes moths, not only in stately homes but in domestic homes too. What a little sweetie it is! And it comes with a fine pedigree, having been used against moths that feed on rice in the Mekong district. The wasp lays its eggs into the eggs of the moth species, and the wasp larvae hatch and gobble up the egg. Rentokil is planning on selling the wasps in time-release sachets – the wasps will hatch continuously, and will then starve to death once the moths are eradicated. Or at least this is the theory.
Trichogramma evanescens (Photo from https://entomologytoday.org/2015/09/21/trichogramma-wasps-used-as-biocontrol-agents-in-the-greater-mekong-region/)
First up though, I do wonder about the broad-ranging tastes of a moth that is happy to feed on the eggs of leaf and stem borer moths in Asia, and also on the various species of clothes moths. As far as I can see, ‘our’ wasp is not native to the UK, and in fact other related Trichogramma species are not found in western Europe. I wonder what other moth species ‘our’ wasp might take a shine to, if it ventures out of the house and into our gardens?
Secondly, my search of the internets finds that the first trial of the parasitic wasp was in Blickling Hall, a National Trust property in Norfolk which is thought to be the birthplace of Anne Boleyn. The house is home to a tapestry given by Catherine the Great in the 1760s, and so there was a lot of concern about an increase in clothes moths during lockdown – moths like to be undisturbed, quiet and dark ( a bit like me on a bad day), and so they had thoroughly enjoyed themselves. The trial started in 2021, alongside the use of the normal pheromone traps, which attract and catch the males, and which can be bought at any hardware shop.
In 2023, however, Blickling Hall abandoned the trial, because it was found that using the wasps plus the pheromone traps gave no better results than using the pheromone traps alone. So why, I wonder, in today’s Guardian, is there an article extolling the virtues of parasitic wasps as a method of clothes moth control? Have the pest control companies just decided to market the insects as a sustainable alternative to spraying?
I suspect that there are lots of ways in which biological controls can be a useful alternative to dousing everything in biocides, but on this one I am feeling just a touch cynical. For me, the worst infestations of moths that I ever discover are inevitably in parts of the wardrobe where I haven’t been for ages, or at the back of the deepest darkest cupboard that I own. Things that i wear and wash regularly are rarely targeted (though there is the odd exception). For me, I think clothes moths are nature’s way of telling me that I should have a clear out. But sympathy to anyone battling these little devils. If it’s any consolation, I have noticed that spiders will often munch on them, so clothes moths are clearly an invaluable part of the domestic ecology. And I would always think twice before getting in a pest control company to deal with them. I suspect that the cure is maybe worse than the infestation.
I agree that the (chemical) cure is probably worse than the infestation. When we first moved to our present house, we were concerned about the termites appearing in our garden. Naturally, we sought advice about their potential danger to our home. Representatives from a pest control company kicked the ground with frowns on their faces, pointed out various humps in the lawn, and grimly forecast that if we left the situation untreated, these little terrors would gobble up the roof trusses and we could find ourselves buried under the weight of clay tiles. Their solution carried an anormous price tag and would have to be repeated every five years. We cringed at the thought of both the money and the chemical injection into every crevice of our home … 36 years later we are still here: we discovered these particular termites, endemic here, do not eat wood and those humps were created by mole rats!
Hah! I’m sure there are some good pest controllers, but all too often in my experience they just want to sell you an expensive, poisonous solution to something that won’t ever be an actual problem.
Completely agree. There is no knowing what else the Asian wasps may take a fancy to, and what other prey they may take to, with damaging results as yet unknown. More research needed, internationally, before we should be taking this risk.
Introducing exotic predators into the environment… what could possibly go wrong?
Your piece reminded me of the line in Bugs Britannica that the presence of clothes moths is a sign it’s time to get the hoover out. So I pulled out BB and read the section again. I was interested to read that there’s a separate species of moth called the Tapestry Moth, once notorious for chewing wall hangings but now reverting to their original habitat of owl nests. I wonder if this is the one they had in Blickling.
Personally I find the odd hole in a cardigan tolerable and don’t try to get rid of moths apart from by hoovering. If a moth is flying around me I try to catch it and put it out of the window in the hope a passing bat or swift might catch up, but they are so fragile I usually just end up with a dusty smear on my fingers.
My late cat Willow would often swipe at a clothes moth and then pick up her paw, gazing in astonishment as her ‘prey’ flew away. Hopeless creature!