We doubt if Einstein actually issued that warning. However, whether the quote is true or not, scientists have described the idea that humans rely on honeybees to survive as a "myth".
Honeybees pollinate many of the vegetables and fruit eaten by humans and that feed livestock.
Now researchers writing in Current Biology say is not true that a decline in the pollinators may threaten the human food supply – creating a "pollination crisis".
The scientists from Argentina and Canada argue that most agricultural crop production does not depend on pollinators.
However, they do warn honeybees are crucial for some of our favorite foods like plums, raspberries, cherries, mangoes, Brazil nuts and cashew nuts.
It is interesting to note that three or four years ago there was a flurry of scare reports in the media about the demise of the honeybee, and how mankind would suffer. As soon as it was discovered that that global warming was not the cause of colony collapse disorder, warnings about disappearing bees slowed to a trickle.
Alarmists are now saying the cause of colony collapse disorder is the use of insecticides.
Some are even claiming that the bee population is actually increasing - see the second link below.
Link here and here.