Hydroxyethyl cellulose-based hydrogel as a novel delivery system for Eucalyptus globulus essential oil and Beauveria Bassiana conidia for the control of the poultry red mite Dermanyssus gallinae.

Background: Dermanyssus gallinae poses a significant global threat to poultry production by affecting animal health and welfare. Conventional acaricidal treatments are limited by the emergence of resistant mite populations and by the risk of chemical residues in eggs and meat. In this study, we evaluated an innovative control strategy based on a hydroxyethyl cellulose (HEC)- hydrogel as a delivery matrix for Eucalyptus globulus essential oil (EO) and the entomopathogenic fungus Beauveria bassiana. Mites were collected from naturally infested hen farms and divided by life stage. Bioassays were conducted under controlled laboratory conditions to compare the effects of treatments applied both with and without pre-incubation of the HEC matrix, expressed as lethal times (LT₅₀ and LT₉₀).

Results: The EO treatment alone or in combination with B. bassiana and without pre-incubation achieved an LT₅₀ of 7.4 ± 0.2 days in adult mites, while the B. bassiana-only treatment exhibited a slightly prolonged LT₅₀ of 8.8 ± 0.2 days. Notably, pre-incubation markedly enhanced efficacy (p < 0.001); the combined treatment reduced the LT₅₀ to 4.9 ± 0.2 days and the LT₉₀ to 10.5 ± 0.3 days, underscoring the synergistic action of EO and B. bassiana. Similar patterns were observed in nymphs, which generally exhibited higher lethal times compared to adults, with strong statistical support.

Conclusions: The findings indicate that HEC-based hydrogel enriched with E. globulus EO and/or B. bassiana conidia is efficacious against D. gallinae. The significant reduction in LT₅₀ and LT₉₀ in adult mites highlights the potential of this approach for integrated pest management. This novel formulation, by harnessing the synergistic effects of E. globosus EO and B. bassiana within a stable hydrogel matrix, may provide a tool for controlling D. gallinae in the poultry industry, thus reducing the use of synthetic acaricides. Results need to be validated under field conditions to provide a sustainable strategy for controlling red mite infestations.