Wild solitary bees and bumblebees are key to high-yielding blackcurrant harvests and larger, more uniform berry size, trials by scientists at East Malling Research (EMR) have revealed.
This was found to be especially important in bad weather. Honeybees, however, were not found pollinating flowers on the nine plantations surveyed and so play little part in the contribution to blackcurrant pollination.
The EMR team, led by entomologist Dr Michelle Fountain, has been growing Ben Gairn and Ben Hope blackcurrants in a series of 12m-long flight cages. The team has been monitoring the success rates of different, native pollinators.
"The results are clear," said Fountain. "With just our wild bees, we achieved maximum pollination in warm, sunny weather on our Ben Gairn trials.
"In the year of the trial, Ben Hope flowered later, during a period of poor weather with low temperatures and 10-15mm of rainfall.
"The fruit set of the blackcurrant was up to 40 per cent lower in the open pollinated bushes compared to those that were supplemented with bumblebee nest boxes," she said. "This is because the poor weather made wild bees less active."
The study has so far identified 13 species of bee foraging for pollen and nectar on blackcurrants.
Fountain is now keen to see guidelines drawn up to help blackcurrant and other fruit growers to maximise pollination levels by developing good local habitats for previously underrated wild bees.
"Good management of local biodiversity and the wider environment plus considered use of pesticides could make all the difference to pollination levels and the quality of harvests," she said.
"Good pollination leads to well-formed, high-quality fruit, which must be every grower's aim."
She added: "The blackcurrant trials, funded by Defra, GlaxoSmithKline and other industrial partners, have told us a great deal about pollination. However, they have also opened up new areas of scientific challenge that we are keen to pursue to provide our fruit growers with even more information to ensure maximum pollination and quality of their crops."
Crop Management - Advice to growers
East Malling Research advice to growers includes careful use of insecticides, especially around the time of flowering when native wild bees may be foraging within the crop.
Other crop management suggestions include ensuring that native bees have access to the different environments they need for nesting and overwintering.
Encouraging a wide range of wild flowers and plants on field margins, mowing flowering alleyways before applying insecticides to avoid spraying foraging bees and nurturing sustainable hedgerows are also listed.