One of the biggest threats to honey bees worldwide is a tiny parasite called the Varroa destructor mite. This vampire-like mite devastates bee colonies by feeding on bee larvae and reproducing inside hives.
Originating from the Asian honey bee (Apis cerana), the Varroa mite jumped to the European honey bee (Apis mellifera) in the 1950s. Compared to the Asian bee, the European honey bee lacks evolutionary defenses against this mite, leading to widespread infestations.
A danger to honey bees
These small, reddish-brown parasites, no larger than a pinhead, wreak havoc on bee colonies. They voraciously feed on the hemolymph (bee blood) of both adult bees and developing larvae. This parasitic feeding weakens the bees, causing weight loss, reduced lifespan, and making them susceptible to various viruses.
The Deformed Wing Virus (DWV), is an alarming example of disease transmitted by Varroa mites. Affected bees display shriveled wings, diminished queen fertility, and early death.
If left unchecked, mite populations can skyrocket. A lone mite in spring can spawn hundreds more by fall’s arrival.
Varroa mites rely on bees to exist
The life cycle of the Varroa mite is deeply intertwined with that of the honey bee. Adult female mites invade bee brood cells just before they’re sealed with wax. Once inside, they reproduce and feed on the developing bee larvae.
As the bee matures and emerges, the mites, having completed their reproductive cycle, exit to find new hosts. Varroa’s prolific reproduction and ability to double their populations every 30 days presents economic challenges for beekeepers. These include dwindling honey yields and escalating management costs to the loss of entire colonies.
Widespread implications for global agriculture
The impacts of Varroa mites extend beyond the hive. Bees, responsible for pollinating roughly one-third of global food crops, are integral to our food security. A decline in their numbers could precipitate reduced crop yields, surging food prices, and potential shortages.
The delicate symbiosis between bees and flowers is at risk, and the ripple effects could be monumental. Our planet’s shifting climate patterns compound the challenges bees face. Rising temperatures can extend mite breeding seasons, allowing more reproductive cycles annually.
Unite for no mites
Addressing this global challenge mandates collaboration across borders. The COLOSS network, involving over 2065 scientists in 121 countries, facilitates vital Varroa mite research and data sharing to accelerate scientific breakthroughs.
Scientists across the globe are working on standardized protocols for evaluating mite resistance and treatment efficacy across geographies. Scientific conferences and workshops help the exchange of information and the spread of new best practices.
Beekeepers' arsenal
To counter the Varroa threat, a diverse approach is essential. Beekeepers employ a variety of cultural, mechanical, biological, and chemical strategies to reduce the number of mites in a particular hive.
Cultural
Drone brood trapping lures mites to bee drone cells, their preferred place to feed and reproduce. The drone frames are then removed and destroyed.
Colony splitting (dividing one colony into two with separate queens) and brood interruption (temporarily removing or caging the queen bee so she can’t lay) can disrupt the mite’s reproductive cycle.
Mechanical
Screened bottom boards let mites fall through the hive and out, reducing their numbers. Beekeepers often combine this approach with a sticky board below the screened bottom board to trap and count the fallen mites.
Chemical
Oxalic acid (an organic compound found in many plants), and formic acid (found in bee and ant venom) are commonly used treatments. They can be effective, but the application method and timing are crucial to avoid harming the bees.
Dusting bees with powdered sugar called a “sugar roll,” encourages grooming behavior, which can help remove mites. The sugar also makes it difficult for the mites to grip onto the backs of bees. Beekeepers who use the sugar dusting method do so only during the late summer or in winter, when there is little to no bee brood (eggs in cells) in the hive.
Biological
Beekeepers are experimenting with the introduction of Stratiolaelaps scimitus, a soil-dwelling mite that feeds on Varroa mites inside the hive. This approach may need to be paired with others, as the Stratiolaelaps will not eat the Varroa that are on adult bees.
Certain strains of the fungus Metarhizium anisopliae show potential in controlling Varroa mites. When the spores of this mold-like fungus land on a Varroa mite, they germinate, drilling down into the mite’s body and killing it from the inside out as it grows.
Fighting back with technology
Scientists and beekeepers are working on innovative solutions to combat Varroa mites while protecting bees. These include:
- Digital hive monitoring using sensors to offer real-time health insights
- Thermotherapy devices that use heat to disrupt mite reproduction
- Predictive analytics to synthesize hive data and forecast mite loads
Early mite detection and treatment is key to hive survival, and new and existing technology will be formidable ally.
The road ahead for beekeepers
The Varroa mite, though diminutive in size, presents a gargantuan challenge. Addressing this challenge required a unified, global effort, that melds scientific research, technological innovation, community involvement, and individual commitment.
