Our beehive screened bottom board features an extra-wide 4-3/4" entrance board and plastic corrugated monitoring tray. A screened bottom board not only increases ventilation in your hive but also assists in monitoring varroa levels. To monitor for varroa mites, insert tray for 24 hours and then count the mite drop. Some run mite drops for 72 hours and divide the total by 3 for the daily number of mites. For more information on mite monitoring, read below.



Natural Mite Drop

Another method to use for determining mite levels is the natural mite drop. A screened bottom board or varroa screen is used to count the number of mites that fall from the colony in a 24 hour period. One advantage is that the hive does not need to be opened to perform the test. One simply counts the number of mites on the tray in one 24 hour period. The test can easily be repeated at regular intervals to determine whether the mite count is increasing.

Screened bottom board & tray use for 24 hour mite drop test

The screened bottom board is used in place of a standard reversible bottom board. The tray slides in from the back. There is no need to use a bottom board unless you prefer to use a hard plastic tray for varroa monitoring.


24 Hour Varroa Mite Monitoring

  • Wipe the tray clean and then coat with a small amount of vegetable oil or petroleum jelly
  • From the back of the hive, slide the tray in beneath the screened bottom board. Do not examine the colony during the 24 hour mite drop period. We are measuring natural mite drop which will be altered if the colony is examined.
  • Remove tray after 24 hour period and count the mites. Mites can be very difficult to see and identify. We recommend using a magnifying glass and a bright light source. They are reddish-brown with a smooth hard outer shell. See picture below:

  • Once you have completed your mite count, record it in your bee journal. We suggest repeating the check every 2 weeks so that trends can be seen. Interpret the mite results using recommended thresholds, below.

Interpreting mite count numbers

Interpreting mite counts is an important step, and recommendations vary based on the method used to count mites and the time of year, as well as other factors. Betterbee is comfortable recommending mite treatment thresholds suggested by the Ontario Tech Transfer Team. See chart below.

Ontario Tech Transfer Team Recommendations

Treat when your mite count exceeds these numbers:

Monitoring Method

Number of Varroa Mites in May

Number of Varroa Mites in August

Sugar Roll

1 mite/100 bees

2 mites/100 bees

Alcohol Wash

2 mites/100 bees

3 mites/100 bees

Monitoring Tray

9 mites/24 hr drop

12 mites/24 hr drop


Screened Bottom Board