Bees are essential pollinators critical to global biodiversity and agriculture. However, their populations face serious threats from a variety of predators and pests that can severely impact colony health and productivity. Understanding these biological threats in detail is vital for effective bee management and conservation efforts.
1. Predators of Bees
Predators are organisms that actively hunt and consume adult bees or their brood. Their attacks can directly reduce bee numbers and stress colonies.
a) Birds
- Bee-eaters (Family Meropidae): These brightly colored birds specialize in catching flying bees and wasps. They catch bees mid-air, remove the stinger by repeatedly hitting them against branches, and then consume them.
- Flycatchers and Swallows: Opportunistically prey on bees during flight or near flowers.
b) Wasps and Hornets
- European Hornet (Vespa crabro): Larger than bees, these hornets attack hives to feed on adult bees and brood. They can kill many bees by decapitating or biting them.
- Asian Giant Hornet (Vespa mandarinia): Known as “murder hornets,” these aggressive hornets can devastate entire colonies. They sting and kill bees, then take the brood back to feed their own larvae.
- Yellowjackets (Vespula species): These wasps often scavenge around hives and may attack bees for food.
c) Mammals
- Bears: Attracted by honey and bee brood, bears can tear apart entire hives. Their strong claws and jaws cause severe hive damage.
- Skunks: These mammals scratch at hive entrances to catch bees flying in and out. They mainly prey on adult foragers at night.
- Badgers and Raccoons: Occasionally feed on hives or bees.
d) Spiders
- Crab Spiders: These spiders hide on flowers and ambush bees as they visit for nectar. Their venom quickly immobilizes prey.
- Orb-weaver Spiders: Capture bees in webs near flowering plants.
2. Pests of Bees
Pests differ from predators in that they often live on or inside the bee colony, feeding on bees, brood, or hive resources, and can spread diseases.
a) Varroa Mite (Varroa destructor)
- Biology: An external parasitic mite, originally parasitizing Apis cerana, now widespread on Apis mellifera. It attaches to adult bees and brood, piercing the exoskeleton to feed on fat bodies and hemolymph (bee blood equivalent).
- Impact: Weakens bees by reducing immunity and vitality. Varroa is a vector for deadly viruses like Deformed Wing Virus (DWV) and Acute Bee Paralysis Virus (ABPV). High infestations can cause colony collapse.
- Control: Treatments include chemical miticides (e.g., amitraz, oxalic acid), biotechnical methods (drone brood removal), and breeding for Varroa-resistant bees.
b) Tracheal Mites (Acarapis woodi)
- These microscopic mites infest bee tracheae (breathing tubes), impairing oxygen flow and causing respiratory stress.
- Infected bees show reduced flight ability and lifespan.
- More prevalent in cooler climates, controlled by good hive management and some miticides.
c) Small Hive Beetle (Aethina tumida)
- Native to Africa, this beetle has spread globally as an invasive pest. Adult beetles lay eggs inside hives; larvae tunnel through comb, feeding on honey, pollen, and brood.
- Their activity ferments honey, causing it to run and smell sour, ruining stored comb and honey stores.
- Control involves traps, maintaining strong colonies, and good hive hygiene.
d) Wax Moths (Greater Galleria mellonella and Lesser Achroia grisella)
- Wax moth larvae burrow through stored combs, feeding on beeswax, pollen, and debris.
- Infestation weakens colonies, destroys combs, and can cause hive abandonment.
- Control measures include freezing combs, using traps, and maintaining strong colonies that can defend themselves.
e) Nosema Species (Microsporidian Parasites)
- Nosema apis and Nosema ceranae infect the bee gut, causing Nosemosis.
- Symptoms include dysentery, reduced honey production, shortened bee lifespan, and colony weakening.
- Spread by contaminated food and feces inside hives.
- Control by fumagillin treatment and improving hive sanitation.
3. Additional Threats: Diseases and Parasites Linked to Predators and Pests
- Many pests like Varroa mites increase the spread of viruses, which can synergistically worsen colony health.
- Secondary bacterial infections and fungal diseases often accompany pest infestations.
4. Ecological and Economic Implications
- Predation and pest infestations can reduce pollination efficiency, impacting crop yields and wild plant reproduction.
- Bee colony losses due to pests and predators increase costs for beekeepers who must invest more in treatments and hive replacements.
5. Integrated Pest Management (IPM) Strategies
Effective bee health management includes:
- Regular hive inspections to monitor pest levels.
- Use of mite-resistant bee strains (e.g., Varroa Sensitive Hygiene bees).
- Mechanical controls like screened bottom boards to reduce mite populations.
- Chemical treatments used judiciously to avoid resistance.
- Good apiary hygiene and avoiding stress factors (poor nutrition, pesticides).
- Protecting hives from mammal predators with fencing or barriers.
Conclusion
Predators and pests of bees represent a complex and multifaceted challenge for apiculture and wild bee conservation. Continuous research, monitoring, and improved management techniques are essential to mitigate these threats and ensure the sustainability of bee populations vital to ecosystems and human food security.