Western honeybees are known to have more than 80 different parasites. Under typical conditions the honey bee's two immune systems are able to control infections. The first is the individual immune system, which is based inside the body of each bee and relies on immune molecules and cells in a similar manner to that of humans. The second immune system is called social immunity and is based on group behaviors. Bees will clean themselves or other sick bees and they may remove infected or dead brood from the hive. As honey bees were moved around by humans they picked up new parasites which are not effectively recognized by their immune response. The lack of immune response allows these parasites to spread easily and cause so much damage that the colony eventually dies. At the top of the list of harmful pests is the varroa mite, which mainly infects the brood of bees. The mites latch onto honey bees and suck their blood. This weakens the bee and also transfers other viruses and bacteria. Another more recently established pest of honeybees is the small hive beetle, whose larvae burrow and tunnel through combs consuming brood, pollen and honey. They also produce a repellent slime so bees do not remove them from the hive. As the combs are damaged honey starts to ferment and colonies collapse and die within weeks.
Industrial agricultural crops rely on chemicals to secure a successful harvest. To protect these monocultures from pests, toxic chemicals are applied to avoid crop losses. Modern pesticides are often systemic—they are not applied to a crop when it gets infected, but are continuously present within the plant, including in their pollen and nectar. Modern agricultural pesticides such as neonicotinoids are highly toxic to honeybees. Unfortunately, they have been deemed harmless because they are systemic and bees are not directly exposed to them. Instead, honey bees pick up small doses of pesticides when they forage for food. Recent research shows that even small exposures of these substances found in nectar and pollen have sublethal effects on bees. The bees are not killed, but the pesticides negatively affect their brain, communication skills and the performance of colonies. Even worse, cocktails of different chemicals amplify such damaging effects on bees.
