Extremely unlikely. Most molds are harmless, and of the few that do contain toxins, odds are either that the cricket wouldn't eat it, or if it did it would be dead. They're not an insect which can store toxins up like some caterpillars.
If it's growing on an orange the most likely culprit would be some sort of penicillin mold which is, as far as I know, not harmful to Ts.
Is their any problem with keeping a chunk of potatoe in the crics cage that would cause them any harm? If i got brown and kinda old... and how long would i be able to keep a potatoe chunk in their before id have to put a new one in?