Using Mite Count Logs to Calculate Treatment Efficacy
Applying a varroa treatment and walking away is not varroa management. It is hoping for the best. Real varroa management includes verification: a mite count before treatment to establish a baseline, and a mite count after treatment to determine whether the intervention worked. The efficacy calculation turns those two numbers into actionable intelligence.
The Efficacy Formula
Treatment efficacy is expressed as a percentage. The calculation is straightforward:
Efficacy (%) = ((Pre-treatment count - Post-treatment count) / Pre-treatment count) x 100
If your pre-treatment alcohol wash shows 3.2% infestation and your post-treatment wash shows 0.4%, the efficacy is ((3.2 - 0.4) / 3.2) x 100 = 87.5%. That is a solid result for most treatments.
If your post-treatment count is 2.8% against a pre-treatment count of 3.2%, the efficacy is only 12.5%. That colony has a serious problem: the treatment did not work, and you need to act.
Why Efficacy Varies
Multiple factors affect whether a treatment delivers its expected result. Understanding the possible causes of low efficacy helps you respond appropriately rather than just retreating with the same product.
Application error. Strips not in full contact with bees. MAQS applied outside temperature window. OAV treatment count insufficient for brood-on conditions. These are procedural failures that can be corrected.
Product degradation. Oxalic acid exposed to humidity or heat loses potency. Old Apivar strips are less effective than fresh ones. Always use product within its labeled shelf life and store it properly.
Resistance. This is the scenario that concerns most experienced beekeepers. If multiple hives in the same yard show consistently low efficacy with a given product, and application procedures are correct, you may be looking at treatment resistance in the local mite population. This is a signal to change products and consult your state extension service.
Timing mismatch. OAV applied when significant brood is still capped will show reduced efficacy because reproductive mites inside cells are not exposed to vapor. The follow-up mite count reflects only the mites that were phoretic at the time of treatment.
Setting Up Your Mite Count Log
A useful mite count log captures, at minimum: date of count, hive ID, number of bees in sample, number of mites counted, and calculated infestation rate. For efficacy tracking, you also need the treatment event that sits between two counts: product, application date, removal date, and any notes about application conditions.
The sequence looks like this for a single hive:
- August 3: Pre-treatment count, 2.8% infestation
- August 5: Apivar strips placed
- September 30: Apivar strips removed
- October 7: Post-treatment count, 0.3% infestation
- Efficacy calculated: 89.3%
That sequence tells you that treatment worked well on this hive. Now compare it across all your hives. Most at or above 85% efficacy is a healthy outcome. Two or three hives significantly below 70% are worth watching for resistance. An entire yard below 70% is a problem requiring investigation.
What to Do With Low-Efficacy Results
Low efficacy on a single hive is often a procedural issue. Review your application notes. Did the strips get full coverage? Was the hive population adequate to ensure bee contact with the strips on both sides? Was the treatment duration correct?
Low efficacy across multiple hives points to either a systemic application problem or emerging resistance. Check your product source. Confirm lot numbers and expiration dates. If everything checks out, switch to a different mode of action for the next treatment cycle and monitor closely.
Document every low-efficacy event with as much detail as possible: temperature, colony population, product lot, treatment duration, and any anomalies observed. This log becomes your evidence base if you eventually need to work with an apiary inspector or extension specialist to diagnose a resistance problem.
How VarroaVault Handles Efficacy Calculation
VarroaVault links mite count events to treatment events so the efficacy calculation is automatic. When you log a mite count after a treatment, the platform identifies the paired pre-treatment count, runs the calculation, and displays the result alongside the treatment record. No spreadsheet math required.
The dashboard view flags hives with efficacy below a threshold you set, so you can see at a glance which colonies need follow-up attention. Over multiple treatment cycles, the efficacy history for a given hive gives you a picture of how well treatments have been working over time.
Pairing the efficacy calculator with the treatment threshold alerts system gives you a closed loop: count at threshold, treat, verify efficacy, count again on schedule. That loop, executed consistently, is what keeps varroa under control in a managed apiary.