Adriana Pacini

Risk factors associated with failures of Varroa treatments in honey bee colonies without broodless period

The treatment against Varroa destructor has become a basic tool in beekeeping practices, mainly during autumn. The treatment effectiveness should be improved by identifying variables affecting the final outcome. The aim of this study was to identify the risk factors associated with the treatment outcome achieved during autumn control of Varroa destructor. The mite infestation after treatment was evaluated in 62 apiaries and data regarding management practices were collected by means of a questionnaire. A mixed-effects model was constructed to associate management variables with the risk of treatment failure occurrence. Colonies with high mite levels prior to treatment (P = 0.002) and owned by beekeepers who did not frequently replace queens (P = 0.001) were associated with a higher risk of treatment failure. Other beekeeping practices indirectly improved treatment effectiveness. An integrated strategy for controlling mites that includes chemotherapy and suitable beekeepers management is needed to keep mite populations low during winter.

Key management practices to prevent high infestation levels of Varroa destructor in honey bee colonies at the beginning of the honey yield season.

Varroa destructor is considered one of the main threats to worldwide apiculture causing a variety of physiological effects at individual and colony level. Also, Varroa mites are often associated with several honey bee viruses presence. Relatively low levels of Varroa during the spring, at the beginning of the honey yield season, can have a significant economic impact on honey production and colony health. Winter treatments against Varroa and certain management practices may delay mite population growth during following spring and summer improving colonies performance during the honey yield season. The aim of this study was to identify risk factors associated with the presence of Varroa destructor in late spring in apiaries from temperate climate. A longitudinal study was carried out in 48 apiaries, randomly selected to evaluate V. destructor infestation level throughout the year. The percentage of infestation with V. destructor was assessed four times during one year and the beekeepers answered a survey concerning all management practices applied in the colonies. We used a generalized linear mixed model to determine association between risk of achieving 2% infestation on adult bees at the beginning of the honey yield season and all potential explanatory variables. The complete dataset was scanned to identify colonies clusters with a higher probability of achieving damage thresholds throughout the year. Colonies that achieved ≥2% of infestation with V. destructor during spring were owned by less experienced beekeepers. Moreover, as Varroa populations increase exponentially during spring and summer, if the spring sampling time is later this growth remains unobserved. Monitoring and winter treatment can be critical for controlling mite population during the honey production cycle. Spatial distribution of colonies with a higher risk of achieving high Varroa levels seems to be better explained by management practices than a geographical condition.

Varroa destructorand viruses association in honey bee colonies under different climatic conditions: Effect of climate on honey bee diseases association

Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee-pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.

Distribution and prevalence of Nosema apis and N. ceranae in temperate and subtropical eco-regions of Argentina

A total of 361 colonies from 59 apiaries located in two temperate and three subtropical eco-regions were examined during the post-harvest period to determine distribution and prevalence of Nosema spp. Apiaries from subtropical eco-regions showed a lower spore count than those from temperate eco-regions. Pure N. ceranae and co-infection were detected in apiaries from all regions. In contrast, pure N. apis infection was exclusively observed in the subtropical study region. The predominant detection of N. apis in a subtropical region joining a southern temperate region where mainly co-infected apiaries were identified is in contrast to previous reports.

Queen replacement: the key to prevent winter colony losses in Argentina

Honey bee colony losses during winter are a multi-factorial phenomenon. Environmental conditions, beekeeping practices and different pathogens are all considered as potential causes of honey bee colony losses. However, these factors may be diverse in different regions and there are no regional studies about winter losses in South America. The objective of this study was to identify risks factors associated with winter losses in temperate climate honey bee colonies in Argentina. Parasitic mite infestation level, colony strength measures, and percentage of colonies losses during winter 2013 were evaluated in 62 apiaries distributed in four different regions in east-central Argentina. Data regarding management practices in each apiary were collected by means of a questionnaire. A logistic regression model was constructed to associate management variables with the risk of winter losses higher than 10% of the colonies. Beekeepers who reported replacing less than 50% of the queens in their apiaries showed higher winter losses than apiaries who replaced more than 50% of their queens (OR = 18.15; CI 95%: 1.76–187.43; p = 0.01). There were no significant spatial clusters detected in our analysis (p > 0.05). Even considering that the winter colony losses can be explained by a complex interaction of factors, requeening appears as one of the most important management practices to reduce this phenomenon in Argentina.

Varroa destructor and viruses association in honey bee colonies under different climatic conditions.

Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee-pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last four years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on DWV amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and Virus presence. This article is protected by copyright. All rights reserved.

Risk factors associated with the abundance of Nosema spp. in apiaries located in temperate and subtropical conditions after honey harvest

Nosema apis and Nosema ceranae are obligate parasites that develop within the honey bee gut reducing the life of their host. The role that they have in colony losses is not clear, and it remains to be elucidated how the geographical and seasonal variations influence pathogenicity of nosema. The aim of this study was to identify risk factors associated with the abundance of Nosema spp. spores in apiaries located in temperate and subtropical regions after honey harvest. A total of 361 colonies distributed in five eco-regions of Argentina were examined to evaluate the abundance of Nosema spp. spores. Regions differed with regard to temperature, precipitation, and vegetation landscape. The abundance of Nosema spp. spores was significantly higher in temperate than in subtropical regions. A south-north gradient of Nosema spp. spore abundance was found, with the highest spore counts observed in South Santa Fe, continuously descending towards the northern regions of higher temperature. The observed gradient may be related to weather conditions and/or availability of floral resources in each eco-region. Also, colonies with >3% of Varroa destructor infestation showed the highest abundance of Nosema spp. spores. N. ceranae, N. apis, and co-infection were identified in 37.77, 26.66, and 35.55% of the studied colonies, respectively.

Prevalence of honey bee (Apis mellifera) viruses in temperate and subtropical regions from Argentina

In Argentina, bee virus studies are still incipient, and there are no studies regarding the climatic effect. The aim of this study was to assess and compare the presence of honeybee viruses in different climatic regions from Argentina. A total of 385 colonies distributed in five Argentinean eco-regions were examined to evaluate the percentage of infestation with Varroa destructor and the presence of seven virus species (Deformed wing virus, DWV; Acute bee paralysis virus, ABPV; Chronic bee paralysis virus, CBPV; Black queen cell virus, BQCV; Kashmer bee virus, KBV; Israeli acute bee paralysis virus, IAPV; and Sacbrood bee virus, SBV) after honey yield. Two viruses, KBV and IAPV, were not detected. The other five viruses were found in different prevalences: DWV (35%), ABPV (21.5%), BQCV (8.0%), CBPV (2.2%), and SBV (1.1%). We found double and triple viral associations in approximately 25% of the sampled colonies. The mean V. destructor infestation in the colonies prior to the acaricide treatment was 7.12%±8.7%. The knowledge of the prevalence of these viruses in the region and their relation with the mite and other possible influencing factors is important for preventing colony losses. Further studies are necessary to identify the risk factors associated with virus presence and its relationship with other pathogens such as V. destructor.

Potential associations between the mite Varroa destructor and other stressors in honeybee colonies (Apis mellifera L.) in temperate and subtropical climate from Argentina

The presence of Varroa destructor in colonies of Apis mellifera is explained by the interaction among a number of factors including beekeeping practices and surrounding environment features. The aim of this study was to evaluate the relative impact of environment geographical region and beekeeping management on Varroa infestation levels throughout a year. A monitoring study was carried out during 2015 in north-central regions from Argentina, consisting of three sampling dates: 1) autumn survey before autumn acaricide treatment; 2) autumn survey after autumn acaricide treatment and 3) spring survey. During these visits, we collected samples for Varroa mites and Nosema sp. presence assessment and information concerning the apiary management practices during each period. Both regional location and beekeeping practices impact on V. destructor infestation level during the course of the year, but relative importance depend partially on the time of year when this was observed. Varroa infestation level is driven simultaneously by a wide-range of environmental factors (regional effect) and honeybee population dynamics. Additionally, colony life histories are also strongly affected by the management practices employed by beekeepers, especially regarding the Varroa mites control and the supplementary feeding. Complexity involving multiple factors interaction in socio-ecological systems like beekeeping is discussed.

Environment and Varroa destructor management as determinant of colony losses in apiaries under temperate and subtropical climate

For the last 10 years, honey bee colony losses have been a topic of interest for researchers around the world, and many drivers for losses were described. The aim of this study was to evaluate the risk factors associated with annual colony losses in apiaries located in regions under subtropical and temperate climate from Argentina. In order to accomplish this, a series of three face-to-face interviews with beekeepers were carried out and samples for pathogens determination were taken from February to October 2015, in North-Central Argentina. A total of 69 apiaries were included in the study. We found that apiaries with high Varroa infestation level before treatment were more likely to suffer higher mortality rates and those beekeepers who used illegal or homemade products (or those that are legal but are not applied according to label instructions) to treat varroa, had more probabilities of having higher losses rate than those who did not treat them at all. Also, migratory beekeepers had higher total losses rate than stationary ones. The eco-regions where the apiaries were located also had differences in their mortality rates indicating a location effect. In the spatial analysis of the losses, six significant clusters with low and high mortality rates were detected within the geographical range. The colony losses rate is a multifactorial outcome, where the environment and the management practices interact in a complex way. Regions that are environmentally suitable for beekeeping can tolerate poor management practices. On the other hand, regions where beekeeping and agriculture share the same area require more careful management to keep colony losses under control. Manejo del medio ambiente y de Varroa destructor como determinantes de las pérdidas de colonias en colmenares de clima templado y subtropical. Resumen Durante los últimos diez años, las pÅrdidas de las colonias de abejas melíferas han sido un tema de interés para los investigadores de todo el mundo, y se han descrito muchas causas de las pérdidas. El objetivo de este estudio fue evaluar los factores de riesgo asociados a las pérdidas anuales de colonias en colmenares ubicados en regiones de clima subtropical y templado de Argentina. Para ello, se realizaron tres entrevistas cara a cara con apicultores y se tomaron muestras para la determinación de patógenos de febrero a octubre de 2015, en el centro-norte de Argentina. Un total de 69 colmenares fueron incluidos en el estudio. Encontramos que los colmenares con un alto nivel de infestación de Varroa antes del tratamiento eran más propensos a sufrir tasas de mortalidad más altas y aquellos apicultores que usaban productos ilegales o caseros (o aquellos que son legales pero no se aplican de acuerdo con las instrucciones de la etiqueta) para tratar la varroa, tenían más probabilidades de tener tasas de pérdidas más altas que aquellos que no los trataban en absoluto. Además, los apicultores trashumantes tenían una tasa de pÅrdidas totales más alta que los apicultores estacionarios. Las ecorregiones donde se encontraban los colmenares también presentaban diferencias en sus tasas de mortalidad, lo que indicaba un efecto de la localización. En el análisis espacial de las pérdidas, se detectaron seis conglomerados significativos con tasas de mortalidad bajas y altas dentro del área de distribución geográfica. La tasa de pérdida de colonias es un resultado multifactorial, donde el medio ambiente y las prácticas de manejo interactúan de manera compleja. Las regiones que son ambientalmente adecuadas para la apicultura pueden tolerar prácticas de manejo deficientes. Por otro lado, las regiones donde la apicultura y la agricultura comparten la misma área requieren un manejo más cuidadoso para mantener las pérdidas de las colonias bajo control.