The Threat Mites Pose to Honey Bees

Of the many threats to bees, mites are not usually the first that come to mind. However, mite infestations pose considerable threats to honey bee colonies, both wild and domesticated. Two types of mites in the US affect hives: tracheal mites and varroa mites.

Tracheal Mites

Tracheal mites are microscopic endoparasites, meaning these mites are tiny and cause damage to the interior of bees. As their name suggests, these mites attack bees by attacking the trachea and respiratory system of honey bees. Tracheal mites move from bee to bee through direct contact, such as when bees feed their young or when bees cluster for warmth in colder climates.

After the bee contracts tracheal mites, the mites lay eggs in the bee's trachea, and the mite larvae will eat through the trachea and surrounding areas. This harms the bee's ability to breathe, leading to bacterial infection and disorientation. Infected bees often show wing issues, including holding their wings at a “K” shape or losing their ability to fly. When bees cannot fly or forage, a colony-wide collapse will soon follow.

Fortunately, most North American honey bees have developed a resistance to tracheal mites. Natural selection for wild bees and selective breeding for domestic bees has allowed bees to build more robust immune responses to tracheal mite attacks. In hives that still suffer from tracheal mites, certain IPM practices, such as re-queening the colony, can help reduce the number of susceptible bees and the risk of colony collapse. Some beekeepers also use grease patties to discourage mites from infecting a hive. These clumps of grease are placed in bee boxes, and as the bees try to move the grease out, they cover themselves in the slick oil, making it harder for mites to smell them and latch on.

Varroa Mites

Varroa mites are macroscopic ectoparasites, meaning these mites are large enough to see with the naked eye and live and damage the exterior of bees. These mites take on a brown/red color and look like ticks on the bees' bodies. Varroa mites exploit honey bee colonies' lifecycle and social structure to infect and damage bee larvae and adults. Mites will initially enter brood cells, where bee larvae develop, to feed on the vulnerable, soft-bodied larvae during pupation. The mites won't kill the larvae but will feed and lay eggs on the developing pupa. Once the bee is ready to emerge from its brood cell, the mites will attach themselves and travel with the bee as it moves around the hive.

Varroa mites can feed on adult and larval bees. While some varroa mites prefer to attach to nurse bees and worker bees as they interact the most with brood cells, drone broods are the most targeted cells. Drones have a longer development period within their brood cells than other bees in the hive, so mites that infect these cells can feed, grow, and reproduce more over a greater amount of time.

The damage caused by varroa mites is significant in many ways. By feeding on the developing bee larvae, the mites open wounds on the bee that are susceptible to bacterial, fungal, and viral infection. The honey bee’s immune system is weakened, and the bee may experience a drastic drop in both body weight and lifespan. The worst damage from varroa mite infestations comes from the physical malformities attributed to feeding on the soft-bodied bee larvae and pupae. Though the mites do not kill the honey bee larvae, serious injuries can devastate their development. Some honey bees may not fully develop or emerge from their cell without dying, and even dead larvae prove problematic to the hive. Worker bees remove dead larvae to make room for new brood, inevitably coming in direct contact with varroa mites and furthering infestation. Without proper management and prevention, varroa mite infestations can cause honey bee colonies to collapse.

Varroa Mite Management

Though varroa mites are destructive, there are some management techniques beekeepers can use to prevent and control mites in bee hives. Integrated Pest Management is the practice of using chemical and cultural techniques to control pests and avoid resistance to one or more control methods. Varroa mite IPM might include frequent monitoring of honey bee colonies and mite populations, cultural adjustments to the hive such as using mite-resistant stock, or changing hive equipment to smaller cell sizes to reduce the number of mites per brood cell. Brood breaks are another control method, wherein the queen is removed from the hive for about three weeks to slow brood hatches and mite prevalence therein. However, brood breaks must be appropriately timed and monitored frequently to ensure the hive does not collapse in the queen's absence.

The EPA has identified and approved 15 different pesticides for varroa mite control in extreme infestations. The EPA recommends regular rotation of any chemicals used to prevent pesticide resistance from developing in mites.

How Mosquito Squad protects pollinators

Mosquito Squad puts pollinators first with our environmentally conscious approach to mosquito control. Our Squad works with local beekeepers across our franchise locations to manage mosquitoes while promoting and protecting bee populations. Contact your local Mosquito Squad today or give us a call at (810) 202-9771 to learn more about our barrier treatment options and beekeeping initiatives.