The reduced size of the common ground-nesting bee, which is a vital contributor to farmed crops, meant that it was only carrying slightly more than half of the pollen it should be.
Researchers, whose findings were published in the journal PLOS ONE, said the effect could cascade down, meaning they would not be able to provide adequate provision for their offspring, who would in turn not reach full size.
Heather Connelly, a graduate researcher of Cornell University in the US, said: "Once we knew there was an effect of agriculture on the size of the bees, we took a random sample of our largest bees from our natural habitats and smallest bees from these agricultural intensive habitats, and looked at how much pollen the female bees were carrying on their bodies.
"Small bees had a 40 per cent smaller pollen load than large bees did, so potentially these small bees might actually be less able to provision their own offspring and we might end up seeing some cascading negative effects on the population of bees there."
Ground-nesting bees, the Latin name for which is Andrena Nasonii (doub corr), are thought to be the most important pollinators of strawberries.
The researchers caught bees visiting strawberries on a range of agricultural landscapes and found that those bees caught on high-intensive agricultural ground were smaller.
Ms Connelly added: "We tended to have smaller bees in landscapes with lots of agriculture around."