In any season, choosing the best varroa destructor mite treatment requires some thought. In summer, however, it is complicated because most beekeepers have supers on their hives to collect honey for human consumption, which limits many of the options for food safety reasons. Explore our guide to learn what varroa mite treatments are suitable when honey supers are on, when to apply each treatment, and which option is best for your apiary.

Varroa mite treatment options for summer use

The treatment you choose depends on a few factors, including mite counts and time of year. Complete regular mite counts to keep an eye on mite populations, which helps determine your ideal treatment schedule.

Though there are numerous mite treatment options for fall, three types of mite treatments are suitable for summer use. These include:

  • Formic Pro
  • HopGuard III
  • Oxalic Acid

Keep in mind that these treatments aren’t one-size-fits-all! Before choosing a summer mite treatment, explore the pros and cons of each and determine which is the best option for your hives. Evaluate which solution will fit your needs using this information about the three summertime mite treatment options.

1) Formic Pro

Of the three products recommended for summer use, formic acid (available commercially as Formic Pro) is the summer mite management mainstay because it has two important features:

  • It can be used when honey supers are in place
  • It kills varroa mites under brood cappings, meaning all of the varroa in the hive are vulnerable to it

However, Formic Pro has one important downside: There is an upper limit on the maximum outside air temperatures during the first few days of the 2-week long treatment period. Ideal daily air temperature maximums are between 50 to 85 degrees F, and temperatures above 92 degrees F in the first three days may result in significant brood, bee, or even queen loss. In areas of the US where summer daily highs remain well above 85 F for weeks on end, Formic Pro is not a suitable treatment option. But in many areas, it is possible to find a slightly cooler, 7- to 10-day summer stretch to get this treatment underway.

Treatment length: 14- and 20-day treatment options.

Note: With all pesticides, it’s important to carefully follow the use and application instructions on the label. With Formic Pro, details about leaving the entrance wide open and the screened bottom board closed are very important to treatment success and safety. So please, take them to heart.

2) HopGuard III

The second useful option for summer, HopGuard III, also allows the honey supers to be in place during the treatment period. However, it is not as effective as Formic Pro at killing varroa mites protected under brood cappings. On the other hand, it doesn’t have the high-temperature restraints of Formic Pro, making it a better choice in areas where daytime temperatures prevent use of formic acid. The active ingredient is made from the hop plant, the same plant that is used to make beer. (Beer, however, is not effective against mites and is best reserved for drinking.)

Treatment length: 30-day treatment duration, can be repeated up to three times per year.

3) Oxalic Acid (in limited circumstances)

The "one-half" option is oxalic acid, which has no upper air temperature limit, making it great for summer use. However, it does not kill varroa protected under the cappings. From time to time, over the course of a summer, these two constraints are sometimes removed by unusual events, making oxalic acid a suitable treatment. An excellent and effective summer use of oxalic acid vaporization is after a new swarm has been hived and settled in, but before there is any capped brood, but any period of broodlessness should be considered as a potential opportunity for oxalic acid. Even in a hive with brood, but without any supers on the colony, a short series of vaporizations may be useful — though less effective — than when capped brood is entirely absent.

During any period of broodlessness when supers are also not on the hive, a single treatment of oxalic acid may provide excellent varroa control. It can be applied in the form of a sugar-syrup mixture which is dribbled onto the surface of the frames or heated in a specialized device, like the Varrox Oxalic Acid Vaporizer or ProVap Bee Vaporizer, with the resulting plume of tiny crystals retained inside the hive.

Treatment length: After the initial short hands-on treatment period, you’ll note dead mites within 24 to 36 hours after treatment. Repeat treatments may be necessary between 3 to 7 days later.

Important note: If oxalic acid is heated (a process often called vaporization), the operators must commit to wearing a respirator equipped with acid gas cartridges when applying the treatment.

Summer mite treatment is an important consideration for beekeepers to reduce varroa populations and improve colony outcomes. However, with summer’s supers and brood, you must choose the correct treatment option. Formic Pro, HopGuard III, and Oxalic acid are often suitable choices if your hives meet the requirements for use. For more beekeeping tips, explore our Guide to Beekeeping.