Rosa M. Manzo

Varroa destructor Anderson & Trueman (Acari: Varroidae) es la especie responsable de la varroosis, enfermedad que constituye la principal causa de mortandad en colonias de Apis mellifera L. (Hymenoptera: Apidae) en el mundo. En el noroeste de la provincia de Chubut son escasos los estudios respecto a esta enfermedad. Por ello, el objetivo de este trabajo fue determinar la dinámica poblacional de A. mellifera y su parásito asociado V. destructor en la región. Se analizó la dinámica poblacional de A. mellifera y de V. destructor, durante la temporada 2022/2023 (octubre- febrero), en tres ecozonas. Los resultados mostraron que hubo diferencias significativas en la cría de abejas a lo largo de la temporada, así como también la prevalencia de V. destructor varió significativamente en abejas adultas. A pesar de que la población total del ácaro presentó diferencias significativas durante la temporada, no se encontró una correlación significativa entre la población total de V. destructor y la dinámica poblacional de A. mellifera. Por lo cual, se sugiere que el clima frío de la región, el manejo sanitario del apicultor y la disponibilidad de recursos alimenticios podrían explicar la falta de un impacto significativo de la infestación por ácaros en la productividad de las colonias. Este estudio aporta información relevante para la sanidad apícola en una región con escasos antecedentes científicos.

Varroa destructor represents a major threat to honeybee colonies worldwide, prompting the search for alternative organic acaricides. This study evaluated the biological activity of essential oils extracted from three Patagonian wild plants—Adesmia boronioides, Dysphania multifida, and Senecio filaginoides—on both V. destructor and Apis mellifera. Chemical analysis revealed that A. boronioides oil was dominated by esquelenone (34.49%), D. multifida by ascaridole (34.87%), and S. filaginoides by α-pinene (40.87%). All essential oils exhibited acaricidal activity, with D. multifida showing the lowest LC₅₀ against V. destructor (1.1 µL/mL at 24 h). Toxicity assays on adult bees indicated that A. boronioides and D. multifida significantly reduced bee survival, whereas S. filaginoides did not appear to cause significant mortality (LC₅₀ = 139.5 µL/mL). Repellency tests for A. boronioides and D. multifida showed significant mite repellence. Larval assays revealed a high survival rate under S. filaginoides treatment (survival rate > 80.24%), in contrast to the reduced viability observed with the other oils. The high selectivity index of S. filaginoides underscores its potential as a selective and safe botanical acaricide. Moreover, its LC₅₀ decreased over time, suggesting a residual acaricidal effect. These findings support S. filaginoides as a promising candidate for sustainable V. destructor control.

Varroa destructor is a parasitic mite, which is considered a severe pest for honey bees causing serious losses to beekeeping. Residual hydrolats from steam extraction of hop essential oils, generally considered as a waste product, were tested for their potential use as acaricides on V. destructor. Four hop varieties, namely Cascade, Spalt, Victoria, and Mapuche, showed an interesting performance as feasible products to be used in the beekeeping industry. Some volatile oxidized terpenoids were found in the hydrolats, mainly β-caryophyllene oxide, β-linalool, and isogeraniol. These compounds, together with the presence of polyphenols, flavonoids, and saponins, were probably responsible for the promissory LC₅₀ values obtained for mites after hydrolat exposition. Victoria hydrolat was the most toxic for mites (LC₅₀: 16.1 µL/mL), followed by Mapuche (LC₅₀ value equal to 30.1 µL/mL), Spalt (LC₅₀ value equal to 114.3 µL/mL), and finally Cascade (LC₅₀: 117.9 µL/mL). Likewise, Spalt had the highest larval survival, followed by Victoria and Mapuche. Cascade was the variety with the highest larval mortality. In addition, none of the extracts showed mortality higher than 20% in adult bees. The Victoria hydrolat presented the best results, which makes it a good compound with the prospect of an acaricide treatment against V. destructor.

Mesofauna represents a major component of soil biological community and play a critical role in maintaining soil quality, as well as a range of ecosystem functions. A split–split plot design was performed with the aim of identifying the main predictors (phytogeographical criteria, cover type and environmental variables) of edaphic community structure under the effect of desertification. The study also aimed to examine the spatial and seasonal distribution of mesofauna community according to phytogeographical criteria (shrubland vs grassland) and cover type (bare vs covered soil) in the north-western Patagonian steppe of Argentina. The relationship between edaphic fauna, environmental variables and site location was investigated using redundancy analysis (RDA), while the main predictors of edaphic community were analysed using generalised linear mixed models (GLMMs). A total of 43 taxa of Oribatida were found in 168 samples. GLMM approaches selected cover type due to its higher effect on mesofauna community. In this sense, cover type was more important than phytogeographical criteria and environmental variables as predictor of mesofauna community. These findings contribute to a better understanding of how the distribution of mesofauna community respond in Patagonia steppe.

A study of oribatid mite communities in a Patagonian forest affected by wildfires was carried out to assess their taxonomic diversity and to increase knowledge of their distribution. A total of 43 species/morphospecies were found. Ten were new records for Chubut and 3 for Argentina. Increased knowledge of this fauna will be fundamental inaiding further understanding about its ecology and distribution.

The lenga forests (Nothofagus pumilio) are the main native forest resource of the Andean Patagonian region. The aim of this research is to inform the species of oribatid mites, and new records, associated to the decomposition process of the lenga wood. Samples of soil and decayed wood were taken under a test of the decomposition process. Twenty-one genera and 26 species of oribatid mites were registered; two of them are new records for Chubut province.

Knowledge of the oribatid mite community from Patagonian steppe is scarce compared with other environments, such as the Andean-Patagonian forest. In the present research we identified oribatid mites under different environmental conditions: two Patagonian steppe types (grass and shrub), two soil characteristics (bare and covered soil) and two different seasons (autumn and spring). A total of 42 species/morphospecies were found, 13 were new records for Chubut and one was a new record for Argentina. In view of its ecological role in soil formation, it is fundamental that knowledge about this fauna is enhanced in order to provide baselines for study and to aid further understanding about its ecology.