In Canada, you might be surprised to learn that the average beekeeper expects to lose at least 10-15 per cent of their hives in the spring. While none of us likes to think about the fact that large numbers of honey bees die, it’s actually a normal part of every colony and it involves a number of factors.
Pests and parasites
The biggest threat to honey bee health is the varroa mite. These parasites feed primarily on the honey bee by attaching themselves to its body and drinking the blood of both the adults and the young. They weaken the honey bees and shorten their life spans making it difficult for colonies to survive the overwintering process. In addition, these mites spread viruses throughout the hive and can be passed on to other hives by drifting worker bees.
Weather and wind
When winters are much colder and longer than usual, it can make it more difficult for colonies to survive the winter. To help honey bees survive, beekeepers bolster the natural measures taken by hives to prepare for the winter months. This includes wrapping the hives, providing extra sugar in the fall, and ensuring a plentiful food supply in the spring. Harsh conditions like wind can also affect crops and reduce the food supply for honey bees.
Bacteria, fungal pathogens and viruses can infect honey bee colonies the same way that they affect people. Certain diseases like deformed wing virus, chronic bee paralysis virus and even plant diseases like the tobacco ringspot virus can have detrimental effects on honey bees, crippling their wings, preventing foragers from collecting food or reducing the competitiveness of drones. These diseases can be spread through close contact or by infected varroa mites, and can quickly affect an entire hive. Similarly, bacterial diseases like American Foulbrood can incapacitate a colony’s young, severely limiting the capacity of the hive to grow, and fungal pathogens like Nosema can significantly affect whole colonies.
Though new innovations in pesticide technology means they’ve become safer over the years, if used improperly pesticides could affect honey bee colonies. Pesticides that could affect honey bees must indicate safety measures on their labels. Certain pesticides are used by beekeepers to protect their hives from infestations of parasites. However these could also affect the health of the honey bees, so care needs to be taken to apply the correct dose at the appropriate time.
Lack of food sources
One of the biggest dangers during the overwintering months is a lack of food. Honey bee colonies work hard over the summer months to collect nectar and pollen and care for their young. Most of the pollen is stored close to the brood or fed to the developing larvae to ensure they develop into productive new foragers. Most of the incoming nectar is dried and stored as honey to sustain the colony over the cold winter months when foraging is not possible. If the beekeeper removes most of the stored honey for harvest, the colony will require some additional feeding with sugar syrup in the fall to bolster their food stores and ensure successful survival into the spring. That means that without proper sources of food, hives won’t have enough to last the winter, leading to a collapse before the spring when they can begin to bolster their numbers again.