Wild insect pollinators improve crop fruit set in ways that adding honey bees does not replicate.
A synthesis across many crop systems worldwide found that wild insect visitation improved fruit set consistently, while honey bee visitation supplemented but did not substitute for it. The mechanisms are understood: buzz pollination, cooler-weather flight and different pollen-carrying behaviour are things honey bees do not do or do poorly.
What this does not claim: This does not claim honey bees are unimportant to agriculture — they are the only pollinator that can be supplied in bulk on demand, which matters enormously. It claims that they do not replace what wild bees contribute.
- Assessment Report on Pollinators, Pollination and Food Production — Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2016) · Systematic review Link