Our allies, the red army

Ladybirds are nature's pesticides. Michael Leapman asks an expert if we will have a bumper crop this year
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THE LADYBIRD is a friend to gardeners, but the kind of friend who is never there when you want her. A predator of pesky aphids (greenfly, blackfly, whitefly and much else that is sent to plague us), the pretty spotted beetle is a comforting sight in our gardens and allotments. The trouble is that it is not a very efficient predator. The aphids invariably triumph, forcing us to resort to sticky and expensive insecticides.

This summer began, as they often do, on a hopeful note. From late April, through the unusually hot run-up to VE Day weekend in early May, ladybirds were seen sunning themselves all across the country. Then came a cold spell and they vanished. As I write, it is unclear whether they were merely sheltering from the chill winds or had been decimated by them.

A leading authority on the ladybird is Michael Majerus, lecturer in genetics at Cambridge University; a genial, gangling man whose transparent enthusiasm for his subject gives him the engaging air of the mad professor of schoolboy literature. His caution in predicting what kind of ladybird summer it will be stems from a sobering experience four years ago, when he suffered a comparable fate to the hapless weather forecaster who assured us in October 1987 that there would be no hurricane.

"In 1991 I got it wrong," Majerus confesses. "It was like this year: there were loads about at the beginning of the summer and I thought we were in for another big year. But it was in fact a little fly parasite that had the population explosion and killed most of them off.

"There have been more than usual so far this year but they don't like the very cold weather and when it comes they go into little shelters. Some will die if there are severe late frosts. It's too early to gauge how badly they've suffered."

He found a vivid example of the effect of cold on ladybirds when he was doing some field work early one mid-May morning. "There were some pairs of them mating but they'd been caught in copula (the scientific term for in flagrante). They were still alive but inactive - I suppose they finished the job off when the temperature rose."

Even if that extended ecstasy were eventually to produce issue, the prospects of the little ladybirds maturing into useful, aphid-consuming members of society are uncertain. Female ladybirds can theoretically produce over a thousand eggs each, but no more than a fraction survive.

Their world is full of predators, beginning at the egg stage, when they are threatened by a militant feminist bacteria that eats only male eggs. This means that the majority of ladybirds are likely to be female. Their name, though, is not a reflection of that but a reference to Our Lady, the Virgin Mary: she is often depicted wearing red, and the seven spots of the commonest ladybird are thought by some to symbolise Mary's seven joys and seven sorrows.

Those eggs that survive the attentions of the sexist bacteria develop into larvae, pupae and then full-blown adults, where they come up against a raft of other lethal enemies. These include parasitic flies and wasps, some other members of the beetle family and even cannibalistic ladybirds. Only birds usually leave them alone: they do not like the taste and the insect's distinctive spotted body, in combinations of red, yellow and black, is a signal to leave it alone.

In some years, though, ladybirds overcome all these natural hazards. Their larvae - black grubs resembling minuscule alligators - are prolific feeders and can consume even more aphids than the adults, who fly from rose to cabbage to nettle, gobbling up the pests as they go. The best year for them in living memory was 1976, when everything came up in their favour.

"To get a glut you have to have a glut of greenfly first," Majerus explains. "That's caused by a mild winter. A lot of aphids die over the winter but without severe frosts they live through.

"The glut in 1976 was caused by two hot summers in succession, with a mild winter in between. In high temperatures ladybirds deve-lop much faster. They can go from egg to adult in three-and-a-half weeks, instead of up to six."

Yet the 1976 bonanza, which left the gardens of southern England virtually aphid-free for a while, was to end in tears. When the ladybirds ran out of aphids they sought other sources of protein, and started to nip people's arms. This proved not so much painful as emotionally hurtful, denting the benign image of an insect we thought we could trust. (The ladybird has always enjoyed popular favour; in Shakespeare's Romeo and Juliet the word is used as a term of endearment.)

By 1977 the aphid population had not recovered, so many ladybirds starved to death, which in turn gave the aphids a chance to re-establish themselves a year later. The odds are usually heavily stacked in favour of the aphids anyway, because they can multiply by a factor of up to 20 within a week - a daunting prospect even for the hungriest ladybird.

There are many kinds of ladybird, differentiated by size, colour and the number of their spots. The commonest is the seven-spot, with seven black spots on a red body. Most other varieties are named according to their spot-count, which can go as high as 24, but that is not as straightforward as it seems: the two-spot, for instance, may have only two real spots but a number of variations in pigmentation that look remarkably like spots to the layman.

The insect is called by a number of pet names in different parts of the country: ladycow, cushcow lady and burnie-bee, or Bishop Barnabee, as in this rhyme:

"Bless you, Bishop Barnabee,

Tell me when my wedding be;

If it be tomorrow day,

Ope your wings and fly away.

Fly to the east, fly to the west,

Fly to him I love the best."

If that lucky swain is a keen gardener, he will welcome the winged messenger as much for its horticultural as for its matrimonial portents. But in real life, how can the rest of us attract these useful creatures? It is not easy, because the only sure way of luring ladybirds is to provide them with a supply of aphids, which seems self-defeating.

Some organic gardeners suggest putting in a crop of stinging nettles. The reasoning is that nettle aphids are among the first to appear in spring, and ladybirds are attracted to them for a good breakfast as they come out of hibernation and deposit their larvae. If you chop the nettles down in late March, the ladybirds should keep the later aphids off your precious plants.

You might also help the ladybirds by picking them up and placing them directly on top of the aphids, for they are not skilled at detecting their prey from a distance: they only recognise it when they have made physical contact. Once they have located one they will do a comprehensive search of the section of leaf or stem where they found it, to mop up its companions.

It is too early to say for certain if 1995 will be another Year of the Ladybird. Gardeners are natural optimists - otherwise they would take up some other hobby - so at this stage we can all hope for a low-aphid summer; and dismiss from our minds the knowledge that, even if this is to be another 1976, it will sure as anything be followed by another 1977. !