>do I still need to worry about varroa crash if I slowly switch them over? if so whats a natural way to help with that?
Any beekeeper needs to learn to monitor Varroa. Pick a method of methods. A sugar roll is a good one. A cupful of bees in a jar with a tablespoon of powdered sugar. Dump the sugar on a paper and count. If you have ten or so, you have a lot of Varroa. If you have none or one or two, you don't have many. A SBB with a tray can be used to do natural drop counts. If you get 50 mites in 24 hours you have a lot of mites. You can uncap some drone now and then and look for Varroa. An occasional one is normal, while three or four per drone is a severe infestation.
If you need to do something, you can use powdered sugar, cut out the drones, or whatever you find acceptable. After they are regressed and you have not had a Varroa problem for a few years, you can probably forget about them.http://www.bushfarms.com/beesfoundationless.htmhttp://www.bushfarms.com/beesnaturalcell.htmhttp://www.bushfarms.com/beespests.htm#varroahttp://www.bushfarms.com/beesvarroatreatments.htm