This is my first year of having a hive and I have Russian bees. Actually Russian cross queen from Kelly Bee company. It was my understanding that Russians were less apt to have Vorroa mite problems. Up until now I have never noticed any mites, however this last inspection I found some larva in the burr comb built between two boxes. Is there an "acceptable amount" that can be in the hive or should I be worried and start to do something about it?