Thesis
FALL AND SUMMER SEASONAL EVALUATION OF A STABILIZED OXALIC ACID FORMULATION (VarroxSan™) FOR CONTROL OF VARROA MITES (Varroa destructor): EFFICACY, TOXICITY AND RESIDUE
Washington State University
Master of Science (MS), Washington State University
05/2024
DOI:
https://doi.org/10.7273/000006924
Abstract
Unlike many other miticides, OA (oxalic acid) has maintained its efficacy and can be applied in vapor or liquid form to control mites. However, treatment while brood is present requires repeated applications, which may be inconsistent and labor-intensive. This highlights the need for an improved formulation to delay/extend its release. It is also challenging to control mites during the summer of the honey production season without the potential of honey contamination and toxicity to honey bees and young larvae during periods of high temperature. To address these critical gaps and provide a more effective varroa control strategy among beekeepers in the United States, this research evaluated the potential impacts of a stabilized OA product known as VarroxSan™. The product is intended to release OA gradually for approximately 42 to 56 days within the colony; this extended release ensures mites are eliminated upon emergence from brood cells and reduces the need for frequent treatment reapplication. This product was tested for efficacy, toxicity, and residue in honey and wax in four treatments in infested colonies over two seasons (40 hives/ fall; 60 hives/summer). Results were compared to the industry standard dose of Apivar® treatment in the fall and, to FormicPro™ treatment in the summer as positive controls, and to a no-treatment control. Follow-up hive inspections, egg emergence, mite counts, honey and wax samples were investigated during the treatments in both seasons. In the fall: after 52 days, we found that VarroxSan™ (1X), VarroxSan™ (1.5X) treatments performed as well as Apivar®, reducing mites/100 bees by 68.9%; 75.2%; and 71.8% and efficacy percentage of 90.5%; 92.4%; and 91.4% respectively; while the no treatment control colonies increased mites/100 bees by 227.3%. No statistical differences were found for toxicity or residue. In the summer: egg emergence rate was 40%, 67% and 87% for FormicPro™, Varroxsan™ and no treatment controls, respectively. Residues levels varied between treatment groups but were not above previously reported natural levels of oxalic in honey. Sticky cards and finishing experiment with artificial brood break allowed estimation for total mite populations during trial period. Based on those numbers' we estimated that FormicPro™, Varroxsan™ 1X, Varroxsan™ 1.5X, and no treatment controls had approximately (9.34±2.48)%, (11.23±4.74)%, (14.30±2.33)%, and (3.59±0.72)% weekly varroa mortality per hive during the treatment period, respectively. This study provides reliable data for the use of this product as a labor-saving, alternative, and valuable integrated pest management (IPM) tool.
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Details
- Title
- FALL AND SUMMER SEASONAL EVALUATION OF A STABILIZED OXALIC ACID FORMULATION (VarroxSan™) FOR CONTROL OF VARROA MITES (Varroa destructor)
- Creators
- Igbagbolere Adeoluwa David
- Contributors
- Brandon K Hopkins (Co-Chair)Walter S Sheppard (Co-Chair)Richard S Zack (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Entomology
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 61
- Identifiers
- 99901124820101842
- Language
- English
- Resource Type
- Thesis