Parasitic Mites

Before parasitic mites entered the United States, a person could purchase a colony of honey bees and expect it to live for a number of years providing pollination service and producing honey. However, the arrival of parasitic mites in the mid-1980s dramatically changed beekeeping in the US. The first mite to be detected, the microscopic tracheal mite, quickly decimated honey bee populations. It was shortly followed by the Varroa mite, a somewhat larger parasite visible to humans. Click on today’s photo of a Varroa mite on a honey bee pupa.

Today, the Varroa is the most deadly parasite of honey bees. As it sucks the bees’ blood, called hemolymph, it vectors at least 15 honey bee viruses to the weakened bees. With the arrival of parasitic mites, the public noticed the absence of bees from locations normally covered with bees; clover fields were often completely devoid of honey bees. Left untreated, most honey bee colonies dwindled and died. Many beekeepers simply quit, abandoning empty hives. Others treated their hives with the miticides, Fluvalinate and Coumaphos. These harsh chemicals killed mites for a period of time, and then they became less effective. New strains of mites, resistant to the chemical miticides, replaced the original pests. Larger doses of miticides brought less control over the mites. Honey bees also experience unfavorable side-effects of miticides. The chemicals accumulate in beeswax honeycomb, contaminating the brood nest. Exposure to the miticides causes sterility of queens and drones which leads to early supersedure of queens and sometimes loss of colonies. These miticides also become highly toxic to bees when exposed to certain common agricultural chemicals. New attempts at controlling Varroa stress an Integrated Pest Management approach based largely on breeding bees that can live in the presence of parasitic mites. To manage bees without using harsh chemical miticides, the beekeeper needs to monitor hives for mites. Symptoms of mite problems include bees with deformed wings or multiple numbers of mites in a drone pupa cell.

--Richard