Note to readers, attached is the complete final report for FNE02-411.
Commercial production of red raspberries (var. ‘Heritage’) that cuts back canes in the Spring to promote synchronous blooming in late July through forest, shifts the bloom period beyond the normal emergency of many native Rosaceous-specializing solitary bees, thus eliminating them as pollinators.
A sampling of three organic farms in central PA in 2002 confirmed the absence of wild honey bees as pollinators of wild and commercial raspberries, and verified the presence of several Rosaceous-specializing native solitary bee species on wild brambles.
Adequate insect pollination for commercial raspberry production is essential and can be achieved by either providing honey bee colonies at 2-3 hives/acre or by verifying that wild bumble bees occur in sufficient numbers.
We propose that observing the visitation rate to raspberry flowers hold the potential to make a conservative estimate of the adequacy of pollination by honey bees, bumble bees or solitary bees individually or in combination. This method combines published honey bee pollination rates with current observations and allows the grower to make immediate adjustments if needed.