Evaluation of efficacy of formic acid and thermal remediation for management of <i>Tropilaelaps</i> and Varroa mites in central Thailand

The western honey bee, <i>Apis mellifera</i>, faces a new threat from the spread of parasitic <i>Tropilaelaps</i> (Tropi) mites, specifically <i>T. mercedesae</i>, which adds additional complexity to an apicultural landscape heavily impacted by <i>Varroa destructor</i> and its associated virus complex. In this study conducted in central Thailand, we investigated the efficacy of two methods of applying formic acid and a thermal remediation technique in controlling Tropi mites and Varroa. We focused our attention on the reproductive stage of the mites, which is restricted to capped brood cells. Results revealed that both formic acid treatments we tested (Formic Pro and liquid formic acid) demonstrated an immediate and substantial reduction in live Tropi and Varroa populations, maintaining near-zero levels for the 3-week duration of the study. In contrast, thermal remediation, employing heating pads, exhibited a more gradual decline, achieving an 85.42% reduction in Tropi mites and a 92.33% reduction in Varroa mites by week three. Both applications of formic acid maintained residual efficacy, continuing to result in dead mites being found in cells 14 days post exposure to the chemical. No dead mites were found inside the cells after the first week of the study in the thermal remediation treatment. Notably, heat-treated colonies experienced an unexpected resurgence in mite populations during week two. The findings contribute valuable insights into potential strategies for mitigating the threat of Tropi mites (<i>via</i> chemical and nonchemical treatment measures) and highlight the urgency of further research to safeguard global honey bee populations.