Question
2 - 3 yr. old weeping cherry blossom tree - many sets of 2 leaves twined together with 1 of the leaves crcled in upon itself and rotting. Also saw very tiny white mite (?) on leaf.  What is it and how do we get rid of it.  Much thanks for your time and help.

Answer
Valerie,

I am not sure exactly what arthropod you are describing, but I don't think that it is a mite.  Mites are very tiny and almost impossible to see with the unaided eye.  Usually, people must use a magnifying glass or hand lens.

Since you've mentioned that the leaves are folded, I suspect you may have either leaf folder insects or tent caterpillars.  Both of these insects are caterpillars when they are young.  You can always remove the insects by hand or squish them.  

Insecticides are often the best remedy for insect problems.  If you want to try an organic product, you purchase Thuricide or Dipel, both of which have the active ingredient as Bacillis thuringiensis. This active ingredient is a bacteria that is selective and only hurts caterpillars.  They can't digest the bacteria and they will die as they eat the leaf (and the product), but it takes some time.  You will have to be sure that you have good coverage and reapply if it rains.

Another insecticide that is quite effective is Sevin.  It is common in garden centers.  You will want to be sure to have good coverage, but it should provide good control of the problem.

Good luck!