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Bob Flowerdew: here’s a smart way
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Val Bourne Pixabay
Gardening Week with Val Bourne, AG’s organic wildlife expert
Harlequins (pictured) outcompete our native ladybirds for food, and eat their larvae and eggs If you have a problem with aphids, don’t spray indiscriminately as you may also kill the ladybirds that eat them
It has been reported that seven out of eight native species of ladybird are declining Our native ladybirds (pictured) are less resistant to being parasitised than harlequins
The lady vanishes
Our native seven-spot ladybird is under threat due to the invasive harlequin that arrived in the UK in 2004, says Val
WE moved to Spring Cottage in November 2004, shortly after the first harlequin ladybird was recorded in Britain on 19 September 2004. Ian Wright, a member of staff in the Department of Genetics, University of Cambridge, spotted an unusual ladybird in a pub garden in Essex and this was the first sighting of the harlequin ladybird in Britain. This ladybird had been introduced into North America in the 1980s, to control aphids feeding on crops. It quickly spread across the USA and became the most common ladybird there. It was also used under glass in the Netherlands and it probably arrived in Britain after being blown over the English Channel on a strong wind. This Asian ladybird is now the most successful invasive alien in the world. The harlequin arrived at Spring Cottage in 2008. We were enjoying a perfect October afternoon in the garden. It was one of those precious days when most of the gardening work has been done. The sky was slightly hazy, and
then we spotted a dark smudge that seemed to be heading for us. A few moments later hundreds of harlequin ladybirds descended on the cottage walls and began to climb into the old sheds at each end of the cottage. Since then, around 100 harlequins find their way into the end bedroom each year and a few roost in my study. I’m not very charitable towards these cannibals, because they devour our native ladybirds. I tend to brush them out the window on a very cold day. However, something strange has happened this year, because there isn’t one harlequin ladybird in my cottage for the first time in years. I’m speculating about the absence of the harlequins. Perhaps it was the very cold spring that held them back. Perhaps there was a shortage of food in the extremely patchy summer we had here, when very hot spells were punctuated by cool, windy, wet weather. Whatever the reason, it’s an indication of how dynamic wildlife is. It doesn’t follow an even line, as there are peaks and troughs, although I suspect my harlequins will be back. On the plus side, I have found more hibernating seven-spot ladybirds than in previous years. Our seven-spot ladybird produces one generation per year and the new adults have to overwinter before they can breed. Each female, once she mates, will lay 500 eggs in clusters of 30, always close to aphid colonies. And we can’t blame just the harlequin for the decline in our native ladybird numbers, as the gardener’s habit of zapping aphids on sight will also have reduced ladybird numbers! Think of aphids as part of your food chain, not as rampaging locusts. Whenever I cut down any plant stems I always try to stack them against the stone walls and I’m constantly trying to leave leaf litter where I can, because that’s where most seven-spot ladybirds hibernate. You find them close to the ground and in rosettes of plants such as foxgloves. In 2015, the UK Centre for Ecology & Hydrology published a paper that stated seven out of eight native species of ladybird were declining and this was strongly linked to the arrival of the harlequin ladybird. It also pointed out that the harlequin ladybird has been shown to be more resistant to parasites than other ladybirds. These parasites develop under the wing case and raise the ladybird’s body. So far I haven’t seen a parasitised harlequin here, but I will keep looking.
Val Bourne
TIP Identifying a harlequin The harlequin ladybird comes in a range of colours, hence the name. It’s rounder than the seven-spot ladybird and generally has two white football-shaped spots on the side of its head.
GREENHOUSES
