Apples from trees pollinated by insects are bigger, rounder, and more desirable, according to new research.
The study, published in the journal Agriculture, Ecosystems and Environment, values the annual contribution of insects to two of Britain's most popular varieties, Cox and Gala, at just under £37 million.
It also says that a lack of pollinating insects, such as bees and hoverflies, could be costing the Gala industry millions of pounds a year.
Dr Mike Garratt, from the University of Reading, led the study.
'Insects are vitally important for producing a marketable number of Gala and Cox apples,' he says. 'To maximise the quantity and quality of apples, we'd need to increase both the abundance and diversity of pollinating insects.'
'That way, when you get a particularly bad season for one pollinator species, there would be a healthy stock of other insects to come in and do the work.'
The research was carried out on six Cox and Gala orchards in the apple-growing region of Kent. At each site, some of the branches were covered with a fine PVC mesh, allowing wind and rain to get through but keeping insects out.
Trees that were left open to bugs yielded both more fruit, and a larger proportion of higher-value class-one apples.
Alongside those experiments, some trees were pollinated by hand. This allowed the scientists to see what would happen if there were enough insects to pollinate the trees to their full potential.
They found that the extra quantity and quality of Gala apples would be worth almost £6 million a year.
Populations of wild pollinators are not currently monitored in the UK. But in the past 30 years, the number of managed honeybee colonies has fallen by more than half. As well as a decline in the number of bee-keepers, both disease and pesticides have been implicated.
A recent study in the journal PLOS ONE said that more than half of European countries, including the UK, no longer have enough honeybees to pollinate their crops, with wild pollinators increasingly taking up the slack.
For orchard managers looking to maximise their yields, Dr Garratt has a number of suggestions.
'Within the orchard, you can help pollinators by planting wildflower strips, maintaining hedgerows, and keeping a proper understory layer to the trees,' he says.
'At the landscape level, what the insects really need are more native grass-lands and woodlands.'
The team are currently carrying out a similar analysis on two other popular British varieties – Bramley and Braeburn.
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More information: Garratt MPD, Breeze TD, Jenner N, Polce C, Biesmeijer JC, Potts SG, 'Avoiding a bad apple: Insect pollination enhances fruit quality and economic value,' 2014, Agriculture, Ecosystems and Environment.