Large-scale field studies are needed to fully understand their effects on the environment.
He also said large-scale field trials of cattle vaccines were being designed, but said a usable vaccine was many years away.
But the F.D.A. said that only large-scale field trials could prove that a vaccine would work in the real world of commercial henhouses.
The effort has also become a large-scale field trial of using classroom video, to help teachers improve and to evaluate them remotely.
The large-scale field, the scientists said, was being generated by the rapid rotation of the extremely dense core object, a black hole or a neutron star, remaining after the explosion of a huge star.
A study in the UK in August provided the first large-scale field evidence that honeybees could also be affected by poisoned nectar carried to the hive from oilseed rape fields.
The European Food Safety Agency is now assessing the evidence for a continuation of the ban and a large-scale field trial in the UK, Germany and Hungary has been completed, with the results due in coming months.
This technique has achieved large-scale field application in China.
