Why Should I Care About Mites?
The Varroa Destructor Mite is considered to be the honey bees worst enemy. They are well known to contribute to colony death and collapse worldwide and were first discovered in the US in 1987. A review of the Brown County Beekeeper Association meeting minutes from that time period indicates that members were hearing about them, but did not appear to be overly concerned. Fast forward 36 years and mites impact each and every beekeeper and bee colony.
Mites themselves don’t kill the bees, rather, it is the many viruses they transmit to the bees that weaken them, including deformed wing virus and acute paralytic virus. In June 2022 Varroa reached Australia, one of the last known places in the world to be invaded by the Varroa Mite Destructor.
OK, Tell Me More!
A responsible beekeeper must perform regular, routine hive inspections, understand and anticipate the bees needs AND have a mite management strategy and plan. To start, let’s talk a bit about mite reproduction and lifecycle. Mites spread via movement of a carrier; a bee, a swarm of bees, a hive, even apiary equipment. They reproduce under capped brood cells and weaken bees by feeding on fat bodies of larvae and bees. Mites are also carriers of a number of viruses harmful to bees and when the mites pierce the bees exterior to feed, the virus’ are transmitted to the bee.
Can I Prevent Mites From Getting Into my Hive?
The short answer is no. There are a number things you can do to minimize the number of mites and to eliminate them when they do show up.
- Maintain a regular monitoring schedule – start monthly mite testing using a sugar roll or alcohol wash in early spring and maintain until late fall. Whenever you receive new bees, test for mites. Don’t get complacent if you get a zero mite count. Do your testing on schedule the next month. Be sure to write down the date and mite load so you can compare month to month.
- Utilize Integrated Pest Management (IPM) interventions – an overview of IPM is shown in the graphic. More in depth info is found here.
How Do I Find Out if I Have Mites?
Two of the most common methods to monitor for mites are the alcohol wash and the powdered sugar roll.
Alcohol Wash – The alcohol wash is considered to be the most accurate method to monitor mite load. Advantages: accurate mite count each time and is quick and easy. Disadvantages: 300 bees are killed in the process of testing and alcohol is flammable – keep away from smoker.
Powdered Sugar Roll – The powdered sugar roll is preferred by many beekeepers because it does not kill any bees, intentionally. Advantages: Bees are kept alive and can be returned for clean-up back in the hive. Disadvantages: method is more time intensive than the alcohol wash and not as accurate. Excessive nectar on the frame which can leave the sample wet and high humidity both can cause the powdered sugar to clump, causing it not to knock the mites off the bees.
I’ve Got Mites, Now What?
Once you know how many mites you have it’s time to decide if action needs to be taken to reduce the number of mites. Divide your mite count by 3 which results in the number of mites per 100 bees (also known as the mite percentage). How many mites is too many and requires an intervention.
Most beekeepers follow this rule of thumb: If the mite load is 9 mites or 3 percent or greater – TREAT. Considering the destruction caused by the mites, many beekeepers are now treating at six mites or 2% threshold. Any early spring count of 3 mites or 1% should be treated due to the exponential growth rate of mites if they are not treated.
The State of Wisconsin produced this guide to mite treatments including treatments not recommended in Wisconsin.
A very well laid out guide for the best treatment options based upon your situation and desires can be found at Honey Bee Health Coalition. Look for the Varroa Management Guide and Varroa Management Decision Tool. Both of these interactive tools are among the best available.