Threats to Honey Bees

Health Problems

Honey bees are facing larger and more diverse threats than ever before. The Four P’s (pathogens, pests, pesticides, and poor nutrition) are longstanding issues, and they are being exasperated by changes in weather conditions, fewer food and water resources, and having to re-establish in new environments. All these factors tend to overlap and interact with one another, which further complicates their survival and productivity. In addition, there are other issues that have impacts on honey bee health, such as the narrow genetic base of honey bees in the United States.

Below are some of the most pressing threats to honey bees and what we’re doing to mitigate these threats.

Parasites and Pests

Varroa mites (Varroa destructor) are essentially a modern honey bee plague. The Varroa mite has been responsible for the deaths of massive numbers of honey bee colonies since its arrival in the United States in 1987. A native of Asia, Varroa normally parasitizes the Asian honey bee, Apis cerana, which is a different species from the European or western honey bee, Apis mellifera, on which this country primarily depends for crop pollination.

Varroa mites directly damage honey bees by attaching and feeding on the fat body of the honey bee. They also indirectly damage honey bees because, similarly to mosquitos, Varroa mites also transmit an array of pathogenic viruses to honey bees such as deformed wing virus.

Beekeepers have identified Varroa mites as their single most serious problem causing colony losses today.

Check out these articles for more information:
Controlling for Varroa mites can help with improving honeybee populations and make bees less susceptible to harmful insecticides
A type of Varroa mite resistant honey bee is more than twice as likely to survive through the winter than standard honey bees.

Small hive beetles, native to sub-Saharan Africa, were first found in the United States in 1996 and had spread to 30 States by 2014. Large beetle populations are able to lay enormous numbers of eggs. These eggs develop quickly and result in rapid destruction of unprotected combs in a short time. If large populations of beetles are allowed to build up, even strong colonies can be overwhelmed in a short time.

Wax moths arrived in the United States in 1998 in Florida. This can be a very destructive insect pest, damaging beeswax comb, comb honey, and bee-collected pollen. Wax moths are rarely the initial cause of colony failure but can overcome weak colonies.

Tropilaelaps mites are the most serious parasites of Apis mellifera in Asia. The parasitic mites feed on honey bees and serve as vectors for viral diseases like deformed wing virus (DWV), one of the leading causes of honey bee colony losses. DWV results in the death of immature brood and  wing deformities in infested adult bees. Because the introduction of tropilaelaps mites into the United States would be added burden to the beekeeping community USDA's APHIS is monitoring the possible introduction of it into the United States.

Pathogens

Since the 1980s, many new exotic pathogens that infect honey bees have been found in this country. These include deformed wing virus, paralytic viruses such as Israeli acute paralysis virus, which was first found in 2004, European foulbrood bacteria, and Nosema ceranae fungi, which arrived in 2005. They have all become major problems for U.S. honey bees and beekeepers.

Check out these articles for more information:
Scientists developed an edible antiviral treatment that can be used to protect honey bees against viruses.
California’s Honey Bee Health Monitoring Network

Poor Nutrition

Honey bees' natural diet comes primarily from nectar and pollen gathered from a wide variety of flowers. Insufficient or incomplete nutrition has come to be recognized as an essential factor that weakens the honey bee's immune systems and is likely to make bees more susceptible to all of the other problems troubling them today.

As demand for pollination services grows, bee colonies often are kept for more time on sites in a mono-crop environment before being moved directly to the next mono-crop area. As more and more land is lost to urbanization and suburbanization, it also means a loss of habitat with a diverse mix of nutritious bee forage plants. In addition, when it comes to helping bee colonies survive the winter and droughts, both times when nectar supplies can be scarce for bees, beekeepers often provide an artificial diet. Scientists are still trying to perfectly duplicate a bee's natural pollen/nectar diet for those times of the year when good forage is not available.

ARS researchers are looking to perfectly duplicate a bee's natural pollen/nectar diet for those times of the year when good forage is not available. They are also studying different food sources that could provide more nutrition and health benefits for honey bees.

Check out these articles for more information:
Pearl millet, an annual grass used for grain and forage, can be a good food source for honey bees and hover flies.
Honey bees are more faithful to their flower patches than bumble bees when it comes to returning to collect more pollen and nectar. 

Pesticides and Sublethal Pesticide Effects

A survey of honey bee colonies conducted in 2010 by ARS researchers looked at 170 pesticides or their residues in honey bees, beeswax, and pollen. The data showed no consistent pattern of pesticide that differed between healthy and Colony Collapse Disorder affected colonies. The most commonly found pesticide in the study was coumaphos, which is used by beekeepers to treat honey bees for Varroa mites.

The pesticide class neonicotinoids (for example, clothianidin, thiamethoxam, and imidacloprid) has been accused of damaging or killing honey bees or being the cause of CCD even when the exposure is below the level expected to be toxic. The nicotine-based neonicotinoids were developed in the mid-1990s in large part because they showed reduced toxicity to wildlife compared with previously used organophosphate and carbamate insecticides.

The scientific data about the impact of pesticides and neonicotinoids in particular at environmentally and agriculturally realistic levels is mixed. Some findings have shown that neonicotinoids have sublethal effects on honey bees at or below approved doses and exposures. Documenting such sublethal effects is very difficult due to the many factors that can influence individual situations in field studies and during grower use including timing of use, health and nutritional state of the bees, total mix of pesticides, pathogens and parasites present, crop type, weather during the growing season, and accumulation of pesticides from year to year. Other studies have indicated that healthy colonies appear not to be impacted.

The U.S. Environmental Protection Agency (EPA) has strict regulations to protect managed honey bee colonies form incidents of pesticide misuse in formulation or application. Tips and complaints alleging pesticide-related bee incidents may be reported to State or tribal authorities or directly to the EPA Office of Pesticide Programs, beekill@epa.gov, National Pesticide Information Center or Guidance for Inspecting Alleged Cases of Pesticide-Related Bee Incidents.

Check out these articles for more information:
Winter honey bees, compared to newly emerged summer bees, have a better ability to withstand the harmful effects of a widely-used insecticide.

Additional Threats

Colony Collapse Disorder

In January 2025, commercial beekeepers began reporting severe losses in commercially managed operations. These losses were reported just prior to almond bloom, the largest pollination event in the world during which more than 1.5 million colonies are staged in the U.S. Central Valley of California for a one-month flowering season. As losses unfolded, it was evident that over 60% of commercial beekeeping colonies had been lost since the prior summer, representing 1.7 million colonies with an estimated financial impact of $600 million.

ARS scientists collected samples across California in February 2025, prior to almond pollination. These samples were analyzed in the Beltsville, MD Bee Research Laboratory for known and novel pathogens (viruses, fungi, and bacteria) and parasites. The results of this research found unusually high levels of deformed wing virus A and B and acute bee paralysis in sampled honey bees from colonies that experienced severe collapse and loss during Winter 2025. These viruses are known to be carried by parasitic Varroa destructor mites, as well as the USDA-screened mites that showed resistance to amitraz, a critical miticide. Research results indicate that rotating miticides throughout the year may minimize miticide-specific resistance. 

ARS researchers will continue to screen honey bees and their colonies for other known stressors and determine the best way to mitigate these stressors, mite infection, and subsequent colony loss. 

Northern Giant Hornet

Northern giant hornets, Vespa mandarinia, formerly known as the Asian giant hornet, are the largest wasps in the world. At roughly 2 inches in length, this invasive species from Southeast Asia has distinctive markings: a large orange or yellow head and black-and-orange stripes across its body.

Though its native range extends from northern India to East Asia, the hornet has been found in western Washington State as well as Vancouver Island and Langley, Canada and is classified as an invasive species in the United States.

The northern giant hornet is a threat to honey bees in its native territory and could also endanger honey bees in the United States if it becomes established here. Recently, the northern giant hornet was eradicated from the United States. ARS researchers will continue to work with state and local governments to detect any future sightings of the northern giant hornet.

For more information, visit our northern giant hornet page.