A grounded synthesis of representative open-access studies on newer and alternative Varroa actives. Every claim is traceable to a cited study.
⚠️ Not label instructions. Several actives here are not registered for Varroa control or are sold only in some countries; others are experimental. Figures are study-reported. Follow your product label and local law. See the decision framework.
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Beta acids from hops (Humulus lupulus) are a natural acaricide delivered on cardboard strips (the product HopGuard). The chemistry is genuinely potent on contact: a 1% topical application of hop beta acids gave 100% mite mortality with no effect on bees, and strips placed in colonies produced strong mite drop concentrated in the first 2–3 days and lasting about a week (DeGrandi-Hoffman 2012). Because it acts on phoretic mites only, it shines in broodless situations — in packages, more than 90% of mites were killed (DeGrandi-Hoffman 2012), and well-timed applications keep mite levels low in colonies started from packages or splits (DeGrandi-Hoffman 2014). Applied to newly split colonies, HopGuard reached ~82.7% efficacy, comparable to amitraz-based products (Aurell 2025).
The catch is delivery: efficacy is sensitive to formulation and application, and at higher exposure hop acids can reduce adult-bee populations (Pettis 2017). HopGuard is best understood as a natural, resistance-free option for broodless windows and splits, not a stand-alone whole-season treatment.
Lithium salts are the standout candidate in recent research. Lithium chloride effectively kills Varroa at low doses and is attractive because it can be fed or trickled and has a simple mode of action (Ziegelmann 2018). In a pre-wintering comparison it outperformed oxalic-acid sublimation at moderate infestation levels (Kolics 2021), and its efficacy has a strong contact component (Kolics 2020).
The unresolved problem is residues and authorisation: lithium is not a natural hive constituent, and it accumulates in honey, in bees and in brood (Prešern 2020), with measurable lithium levels building up in bees and bee products after treatment (Kolics 2021). Until residue behaviour is fully characterised and the compound is authorised, lithium chloride remains a highly promising but not-yet-approved option (Kolics 2021).
Resistance to the established synthetics has spurred a search for genuinely new chemistry:
A parallel strategy is making proven organic acids work better. Bee-safe adjuvants that increase spreading and penetration sped up and strengthened the miticidal effect of oxalic acid in glycerin strips, pointing toward more reliable extended-release formulations (Shannon 2025).
Of the emerging options, hops beta acids are available and useful now — a natural, resistance-free choice for broodless periods and splits, limited mainly by delivery. Lithium chloride is the most exciting candidate but is gated on residue science and regulatory approval. New synthetic modes of action like chloride-channel blockers matter most as resistance-breakers for operations where amitraz or the pyrethroids have failed. None of these removes the underlying need for the integrated, rotate-and-monitor approach the rest of this section describes (Rosenkranz 2010).
DeGrandi-Hoffman et al., Experimental & Applied Acarology 2012 · 16 citations — 100% mite mortality on contact; >90% in packages; the broodless/package use case.
Aurell et al., Journal of Economic Entomology 2025 · 2 citations — HopGuard at ~82.7% in splits, comparable to amitraz.
Ziegelmann et al., Scientific Reports 2018 · 27 citations — The foundational lithium-chloride efficacy study.
Kolics et al., Acta Veterinaria Hungarica 2021 · 16 citations — Head-to-head efficacy advantage, with the authorisation caveat.
Vu et al., Pesticide Biochemistry and Physiology 2020 · 8 citations — A new mode of action effective where pyrethroid/OP acaricides had failed.
Prešern et al., Food Chemistry 2020 · 13 citations — The residue question that gates lithium's adoption.
Curated synthesis — not exhaustive, and not a substitute for the product label. Related: Decision framework · Oxalic acid · Biotechnical control · Acaricides & resistance · Treatment calendar.