The leaves are infected with a microscopic mite, an eriophyd mite. The leaves should be treated with neem early in the growing season as once the leaves start to curl its difficult to get the neem into the affected areas. This problem was discussed about two months ago at my bonsai club and the advice was given by a county extension agent.
This may be a good explanation, thanks for the info.
The only question is, was this aphid actually seen and identified with a microscope by somebody, or is it an educated guess?
Treating with
neem oil may be a good solution for somebody with one or two small bonsai, but for someone in my shoes, where I have a 20 feet tall, fully grown pomegranate tree in my backyard, and another group of 25 small trees growing in the ground for future bonsai it would be impossible to cover my whole backyard with ten gallons of neem. I imagine that if you eradicate the whole population of these aphids in your backyard, and just a few of them survive on some leaves that were not treated (or their eggs may survive from the last season), then they will be back again next year.
It is also interesting to see how specialize these things are: strictly the pomegranate leaves are affected, and all the other species around it are totally untouched by them.
But, as I said, they never did any noticeable harm, so I just leave them alone.