Formic acid is one of the most popular treatments for controlling Varroa mites in bee colonies.

It’s particularly favored for its ability to penetrate capped brood cells and target mites where they reproduce.

However, timing and temperature are critical when using this treatment, especially as winter approaches.

The Role of Temperature in Formic Acid Treatments

Formic acid relies on its ability to vaporize and distribute evenly throughout the hive to kill mites effectively.

For this process to work, external temperatures must remain above 50°F (10°C).

Below this threshold:

The acid doesn’t vaporize adequately, leading to uneven or ineffective treatment.

Low temperatures could cause the treatment to remain in the hive, potentially harming the bees.

This means that as the colder months approach, using formic acid may no longer be a viable option for treating your hives.

Plan Your Treatment Window

To maximize the effectiveness of formic acid, plan your treatments during the fall when:

Temperatures are consistently within the recommended range of 50-85°F (10-29°C).

Colonies are still active and preparing for winter, allowing them to recover from the treatment and build up their winter bee population.

Alternatives When Temperatures Drop

If you miss the optimal window for using formic acid, consider other treatment options that work in colder weather.

Oxalic acid vaporization, for example, can be effective against Varroa mites during broodless periods in winter.

This method doesn’t rely on high temperatures, making it a suitable alternative when formic acid is no longer an option.