What kills most bees?

What kills most bees includes combination of natural and human caused threats, with habitat loss, pesticides, parasites, and diseases being leading causes of bee decline, particularly for honeybees and wild bees. The single biggest killer for managed honeybees is Varroa destructor mite, parasitic mite that feeds on bee blood and spreads viruses that weaken and kill colonies, causing colony collapse and considered major threat to beekeeping worldwide, with many colonies lost to Varroa infestations. Pesticides, especially neonicotinoids, kill bees by poisoning them and affecting navigation, reproduction, and immune system, and are major human caused killer. Habitat loss and lack of flowers due to monoculture farming, urbanization, and removal of wildflower meadows reduces food sources and nesting sites, leading to starvation and decline. Diseases like American foulbrood, European foulbrood, and Nosema fungal disease kill larvae and adults. Environmental factors like climate change affect flowering times and bee emergence. For wild bees, habitat loss is biggest killer. Natural predators like birds, spiders, and wasps kill individual bees but not colonies. So what kills most bees is combination, but Varroa mite is biggest killer for honeybee colonies, while habitat loss and pesticides are biggest for wild bees, and addressing these through reducing pesticide use, planting bee friendly flowers, and managing Varroa is crucial for bee conservation.