@Mamako The most effective treatment for varroa mites in Italian honeybees is known to be Apivar, Apistan, or formic acid treatments. However, it's important to follow the instructions carefully and seek advice from experienced beekeepers or professionals before choosing a treatment method.
The number of brood boxes needed for your Italian honeybees to survive the winter in North Carolina along the Atlantic Coast depends on multiple factors such as local weather conditions, strength of the colony, and available food sources. Generally, 2 deep brood boxes or 3 medium brood boxes should be enough to overwinter a hive in that area. It's always best to consult a local expert to get specific recommendations.
In general, it's better to purchase beekeeping supplies from reputable local suppliers who can provide support, advice and knowledge relevant to your local conditions. However, if you cannot find something locally, Amazon can also be a viable option, but it's important to research and read reviews before making any purchases.