Summer Varroa Control That Won’t Spoil Your Honey: What Oxalic Acid & Glycerin Strips Can and Can’t Do
- Frank Jeanplong
- Jul 27, 2025
- 2 min read
This study provides essential insights into a low-residue, moderately effective summer treatment for Varroa destructor using oxalic acid and glycerin strips. While not a silver bullet, the method outperformed both 65% formic acid and oxalic acid dribble in mite reduction - without harming colony strength, queen status, or honey quality. If you’re looking to curb summer mite growth without risking honey contamination, this research shows how to integrate this tool safely into your IPM strategy.
1. Moderate Mite Control Efficacy
Oxalic acid and glycerin strips reduced Varroa destructor levels by 55.8% over 42 days.
This was significantly more effective than:
65% formic acid (42.6% efficacy)
Oxalic acid dribble (39.5% efficacy)
The maximum efficacy in individual colonies reached 85%, but the average was moderate.
Takeaway: While not strong enough as a stand-alone treatment, this method is valuable in slowing summer mite population growth within an Integrated Pest Management (IPM) plan.
2. Low Impact on Bee Health
The study found no significant negative effects from oxalic acid and glycerin strips on:
Colony strength (cluster size)
Worker bee mortality
Queen status
Colony survival through winter
Takeaway: This treatment appears bee-safe, making it an attractive option compared to harsher treatments like formic acid.
3. Temporary Effects on Brood Pattern
Colonies treated with oxalic acid and glycerin had a temporary increase in spotty brood patterns, especially noticeable at:
7 days (54% of colonies affected)
14 days (69%)
28 days (51%)
Recovery to uniform brood was observed by day 45.
Similar temporary brood pattern disruptions were seen with formic acid.
Takeaway: While brood disruption may occur, it’s transient and not associated with long-term harm or queen loss.
4. No Residue Concerns for Honey
Oxalic acid residues in honey from treated hives were not significantly different from untreated controls during or before treatment.
In fact, post-treatment honey from treated colonies had lower oxalic acid levels than the control group.
All levels were well within natural background levels of oxalic acid found in honey.
Takeaway: Safe to use during or near honey flows - no risk of contaminating marketable honey.
5. Supports IPM but Not a Stand-Alone Fix
The study stresses that oxalic acid–glycerin strips should not replace other treatments.
They are best used as part of a seasonal control strategy, especially for managing summer mite growth and delaying exponential build-up before fall.
Takeaway: It’s a useful mid-season tool, especially when other options are limited or can’t be used during honey production.
Final Note for NZ Beekeepers:
Though conducted in Canada, the northern climate conditions are relevant to many parts of New Zealand's temperate zones. The oxalic acid–glycerin method could offer a practical, affordable, and bee-safe tool to manage varroa in summer - especially important for hobbyists and organic beekeepers.
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