Will ladybirds harm my plants?


This year I have hundreds of ladybirds descend on my sheds etc. Will they do any harm to my plants? I have petunias in my hanging baskets and some of the flowers have small holes in them – is that the laydbirds, or something else? (Peter Turner, via email)


Ladybirds will do no harm at all to the plants – in fact they work hard for the gardener clearing aphids and other small insects that predate plants. As gardeners, our high regard for these small creatures is not unfounded for they are one of our best deterrents against garden pests.

Most ladybirds are carnivorous, their particular favourite food being greenfly. They will also eat small caterpillars and they will take mealybugs, mites and even some scale insects. They help pollinate plants as they move from flower to flower.

Ladybird larvae have a spiky, segmented body with powerful jaws and a ferocious appetite for aphids – no wonder that they are often referred to as 'insect alligators'. Take care not to harm them. The more that survive then the better will be your natural defence against pests.

Ladybird larvae look nothing like the adult but are the more useful to gardeners as they are out in spring when the new aphid attacks start. Starting as a tiny, shiny, yellow egg, laid in a cluster on a leaf, the ladybird passes through several stages before reaching the adult beetle we are so familiar with. Each egg hatches to release a small, black, sixlegged larva which eats greedily and increases in size by shedding its skin three times in its lifetime.

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The full-grown larva eventually attaches itself to the leaf and forms a pupa, from which the adult beetle emerges one to two weeks later. Ladybirds emerge from hibernation in late March/April.

Beetles and larvae feed through the summer; the larvae pupate and produce a new generation of beetles during mid to late summer. These beetles feed and look for hibernation sites. Few of the older (one year) beetles survive to hibernate a second winter.

Their bright colouring is said to warn birds of their awful taste.

Of the 42 different species of ladybird in the UK the most common is the sevenspot ladybird. It is thought to have inspired the name ladybird: 'Lady' referring to the Virgin Mary (Our Lady) who in early paintings is seen wearing a red cloak; the seven spots are symbolic of the seven joys and seven sorrows of Mary.

The reason you have seen lots in your garden on your plants is likely to be because you have got an aphid problem on your plants and the ladybirds have come to clear it up for you!

•This article was first published on August 20, 2011.