Australia is bracing itself as the bee honey industry is being threatened by the spread of the bloodthirsty Varroa mite parasite and goodbye to bees!
All beekeepers are on the alert to stop the outbreak, after bees around the port of Newcastle in NSW, were first found to have the deadly parasite. Millions of honeybees have already been exterminated in a bid to prevent the parasitic plague from spreading.
Queensland and Victoria are watching the spread closely in case they need to take the critical action of ‘bee lockdown’.
The Varroa mite infestation comes at a moment when the country’s agricultural industry is already dealing with high energy prices due to the Russia-Ukraine war, supply-chain issues, bushfires, floods, a previous mouse plague and a covid hit workforce.
1. What is the Varroa mite?
Varroa mite is the most threatening pest of honeybees worldwide. The disease caused by the mites is called Varroosis.
Varroa mites have two varieties, the Varroa destructor and Varroa jacobsoni, both weaken and kill colonies while transmitting viruses.
They are tiny reddish-brown external parasites of honeybees, shaped like a scallop shell, about 1.1mm long and 1.7mm wide. They feed off adult honeybees and of the honeybee ‘brood’, that is, the eggs, larvae, and pupae of the honeybee.
2. How does the Varroa mite harm bees?
Varroa mites are one of the most destructive pests for honeybees. They live and reproduce on larvae and pupae in the developing brood, causing deformation of the wings and bodies as they emerge as adults. They also feed on adult bees’ haemolymph(the bee’s equivalent to blood).
The Varroa mite shortens the honeybees’ lives. They or cause them to die by transmitting many more viral infections that otherwise would cause little harm.
Heavy mite infestation causes crippled and crawling bees, a reduction in the honeybee population ending in total colony breakdown and death of the hive.
Mite numbers increase slowly within a hive. It may not be until the fourth year of infestation that numbers are sufficiently high for honeybee larvae to be parasitised by several females.
3. How can the varroa mite impact food supply in Australia?
A good proportion of the food we eat from fruits to nuts to vegetables is dependent on bees for pollination. Due to the Varroa mite crippling the bee’s ability to fly, gather food and pollinate then the agricultural farmers’ livelihoods will be severely threatened if the mite spreads to the wild honeybees.
Areas around the hive are affected by reducing the pollination necessary to produce fruits and vegetables.
A widespread Varroa mite outbreak would have a catastrophic effect on Australia’s agricultural industry. Almonds, berries, apples, and avocadoes are some of the 35 agricultural industries reliant on bee pollination. Not to mention the devastating effect on honey supplies. Luckily, Varroa mite does not get into the honey.
Shoppers are already having to face higher prices for fruit and vegetables, after the floods and staff shortages, so it is vital that Australia takes emergency lockdown measures to get the mite under control and a barrier in production would obviously affect prices.
Honey exports would be hit, and people would lose jobs. Beekeepers are being asked to monitor hives for Varroa mite and report sightings. Varroa is the most serious pest of honeybees inflicting more damage and higher economic costs than all other apicultural diseases.
4. Is the Varroa mite easy to detect?
Whilst Varroa mite can be detected by the naked eye in slightly infested colonies they are found in sealed brood cells. The mites may be seen on drone and worker pupae in cells but to see them, the cells need to be uncapped and the pupae removed for examination.
Colonies which have been too long in the wintering mode and have no honeybee brood might have the female mites found on adult bees. They are found hidden between the sclerites, a component of an exoskeleton, between the first abdominal segments of an adult honeybee.
5. How does the Varroa mite spread to other colonies?
Considering the Varroa mite has only very short legs or wings it has no trouble getting around on the public transport system, built and maintained by the honeybee host they parasitise.
The most common ways the Varroa mite may spread are: –
- By hitchhiking on infested honeybees and contacting bees that have not been invaded.
- By honeybees form healthy robust hives raiding the honey from a weaker hive riddled with Varroa mites, the robbing bees then take the honey and the blood-thirsty Varroa mites’ home.
- By hitchhiking from a flower that a Varroa-laden bee has groomed itself on and dislodged the mite onto the flower.
- By a beekeeper exchanging frames of bees or brood hives allowing the mites to easily move between colonies.
- By introducing previously used beekeeping equipment, packaged bees and queen bees are infested.
6. How did the Varroa mite get to Australia?
It is hard to identify where how the Varroa mite entered Australia, but it most likely got here by hitchhiking on live bees that were transported or in shipments of bee-keeping equipment that had been used recently. It is illegal to import live bees or used beekeeping equipment unless it has been certified by the authorities.
Varroa mites were originally found only in Asia as parasites on the Asian honeybee. Until recently Australia was one of the few countries which were Varroa mite free. In 2018 Varroa mite was detected in Victoria in a swarm of European honeybees which arrived on cargo. Varroa mite is the biggest threat to bees worldwide.
Australia is fighting to contain this 2022 outbreak after it was found in a port in the state of NSW and then detected in hives hundreds of kilometres away. Beekeepers in Victoria, South Australia and Queensland are at risk if New South Wales cannot stop the spread.
In Australia, the spread of varroa is expected to be fast over long distances because of the migratory nature of the beekeeping industry.
7. What is being done to stop the spread of the Varroa mite?
Authorities have introduced several biosecurity measures to limit the outbreak after the mites were detected across New South Wales. A ‘bee lockdown’- a movement control order restricting the movement of bees across the state is being enforced. The state is restricting the movement of bees, beehives and bee products including honey.
Any hives within the infested locations will also be destroyed, meaning millions of honeybees of already been exterminated by the Australian authorities. While colonies within 25km will be inspected and monitored.
Any hives in which the mites are detected are destroyed. It is hoped that with the biosecurity zones in place, the surveillance system will do its job to stay on top of where the Varroa mite is hiding!
8. Are there bees which are resistant to the Varroa mites?
Varieties of bee stocks with mite-resistant traits have been developed. Russian bees are one variety which inhibits mite reproduction.
Mite-resistant honeybee stock can reduce the reliance on chemicals for Varroa mite control.
Varroa Sensitive Hygiene bees can detect and remove mite-infested pupae.
Ankle biters or leg chewers are bees which bit the mites, harming their legs or bodies.
9. Which mechanical controls can be used to prevent and control Varroa Mite?
- Research has suggested that a small hexagon cell size, like the size bees, have in the wild, can decrease mite numbers.
- If the queen is removed from the colony for about 3 weeks, then a “brood break’ is achieved. This means that the number of available brood cells for mite reproduction are available.
- Screened bottom boards can be introduced to assist in discarding mites that fall to the bottom of the hive when they fall through the screen onto the ground, some distance from the colony and any bees.
- Powdered sugar dusting can be effective in reducing the mite population in broodless, or nearly broodless bees. Powdered sugar does not kill the varroa mites, but causes the mites to drop to the bottom
10. Which chemicals can kill mites?
Pesticides which can be used as miticides (kill mites) are in two categories soft chemicals and hard chemicals.
- Soft chemicals include formic acid, oxalic acid, essential oils like thymol, and potassium salts of hops beta acid derived from hops.
- Hard chemicals which are used to control mites are called acaricides or miticides. Of the synthetic miticides.’mitraz’ is the most popular. However, mites can develop a resistance to these chemicals and residues linger and accumulate in the wax.
- Natural chemicals include food-grade mineral oil in a propane fogger – apparatus used to spread a fog of the pesticide. The mineral oil puts a coat on the bees and mites making the bees groom each other and the mites fall off. Powdered sugar works in the same way as mineral oil, stimulating grooming behaviour.