Not sure anyone can shed some light on this problem. The last 2 years I have noticed very high failure rates on my crabapple bench grafts. Did not have the problem previously. I have a very high take on all other apple varieties. I am a bit stumped. Only thing I can possibly think is that I am collecting scion wood too late into the winter. Crabapples tend to leaf first so maybe they are ready to break dormancy with just a little heat? Not callusing before they break dormancy. They break bud and then die within a week.
What kind of crabapples are they? Could it be a compatibility problem?
No. I have grafted and grown successfully in the past on the same root stocks. Hewes, Dolgo and Chestnut. I have had other crab apples sent to me to graft from others and have good success with them all taking the last two years. They are grafted at the same time as all other varieties.