Dean, speaking at the Prognosfruit conference held earlier this month in Kent, said that - unlike almond growers who want every flower fertilised for a full crop - apple growers are fearful of the need for hand thinning if too many apples set. However, he warned the top fruit industry that misshapen and undersized fruit could result from poor pollination and that fruit may not stay on the tree until harvest - and may not even store as well.
"Honeybees are in serious trouble around the world," he warned. Varroa mite-spreading viruses have led to weakened colonies, which are now also being affected by colony collapse disorder (CCD), he said.
The situation in the UK is perhaps worse as declining beehive numbers are coupled with an aging population of beekeepers (the average age is 58). Dean believes the real figures for European honeybee decline are much worse than official statistics show, due to the numbers of small beekeepers who only registered for the first time when the Varroa mite started becoming a problem.
He thinks that there has been a 50 per cent loss of honeybees in the UK - with wild colonies now almost non-existent.
Growers, he said, need to think about new strategies to encourage natural wild pollinators and consider introducing specially selected native solitary bees.
Dean is working with a native species, which as a pollinator is 180 times more efficient than a honeybee, and is also investigating the possibility of using bees to deliver biological control products straight to the flower.
To combat the pollinator decline, growers should make changes to their orchard management.
Making use of integrated pest management schemes is essential but growers should avoid applications when the weather is favourable to pollinators.
Actively encouraging native wild pollinators is vital, and growers, he said, should create nesting areas such as sand banks. They should also supply a long-term food source - both before and after the orchard-flowering period. Dean recommended planting red clover in the alleys, which could be mown selectively to give alternative food when there was no or few apple flowers open and then stripped of flowers during the main pollination time but allowed to flower again as apple flowering finished.
Addressing the issue of using wild pollinators, Dean explained that fruit growers, who would otherwise have to pay to hire honeybee hives at flowering time (£45 each), should take this "free service". He added that just by changing orchard practices growers are in this way actually "investing in a free service" from wild pollinators.