Magiver

I just had this same problem, i picked up some shultz houseplant & gardens insect spray, it worked really good and kills aphids on contact and its not made of strong chemicals that will hurt your tree, its actually made of chrysathamum flowers and worked very good for me. you can read treebays reply to my question on the best way to take care of them here: http://www.memobug.com/treebay/cgi-bin/YaBB/YaBB.cgi?board=pests&action=display&num=1006302063