if your silk thread is fraying it is caused from the wrong needle or too long of pieces- you should use about 18" of thread on your needle- and a needle with a round eye helps- but it could just be the needle is too tiny- use a bit larger needle-and shorter thread length's and you probably will not have fraying problems-
i do alot of applique & love silk threads- but do use other threads too- the color is the deciding factor- i do have a good selection of silk colors though- when i can that's what i use most.