The bacterium Paenibacillus larvae and the mite Varroa destructor are two of the most severe biotic stressors affecting honeybees and are responsible for American foulbrood and varroosis respectively. To control these pathogens, beekeepers regularly apply synthetic acaricides or antibiotics to parasitized hives. However, antibiotic and acaricide overuse over time leads to resistance in bacteria strains and mite populations respectively, not to mention the residual contamination of bee products with these chemicals. The development of alternative and effective control methods of bee diseases is therefore crucial. In recent years, natural substances from plant extracts have emerged as the basis of suitable control methods to treat bee colonies parasitized by both P. larvae and V. destructor . Our aim was to evaluate the bioactivity of ethanolic and methanolic hop leaf extract (species: Humulus lupulus L, varieties: Victoria, Spalt, and Cascade) against P. larvae , V. destructor , and A. mellifera . The bactericidal activity against P. larvae was evaluated by the broth microdilution method. Topical administration protocols were used to determine the bioactivity of hop extracts on V. destructor and A. mellifera . Total polyphenols, flavonoids, saponins, and antioxidant capacity were determined for each hop leaf extract tested. The Victoria extract had the highest concentration of phenolic compounds, whereas Cascade and Victoria extracts had higher concentrations of the glycoside saponin. All hop extracts presented low toxicity against A. mellifera bees after 48 h of topical administration (except for Cascade ethanolic extract which reached a maximum of 36% of bee mortality). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranged from 0.69 to 2.75 mg/kg for the Cascade variety, 1.38 to 5.5 mg/kg for the Spalt variety, and 5.5 to 11 mg/kg for the Victoria variety. After 48 h, the acaricidal activity for the ethanolic extract of the Victoria variety reached a value close to 80%, while the methanolic extract of Cascade showed an acaricidal activity close to 70%. The results reported in this study support the potential use of methanolic and ethanolic extracts of hop leaves from Argentina as promising natural alternatives for varroosis and American foulbrood control.Paenibacillus larvae / Varroa destructor / Apis mellifera / natural extracts / Humulus lupulus / chemical composition

Although mitochondrial DNA mapping of Varroa destructor revealed the presence of several haplotypes, only two of them (Korean and Japanese haplotypes) were capable to infest Apis mellifera populations. Even though the Korean haplotype is the only one that has been reported in Argentina, these conclusions were based on mites sampled in apiaries from a specific geographical place (Buenos Aires province). To study mites from several sites of Argentina could reveal the presence of the Japanese genotype, especially considering sites near to Brazil, where Japanese haplotype was already detected. The aim of this work was to study the genetic structure of V. destructor populations from apiaries located in various provinces of Argentina, in order to determine the presence of different haplotypes. The study was carried out between January 2006 and December 2009. Phoretic adult Varroa mites were collected from honey bee workers sampled from colonies of A. mellifera located in Entre Ríos, Buenos Aires, Corrientes, Río Negro, Santa Cruz and Neuquén provinces. Twenty female mites from each sampling site were used to carry out the genetic analysis. For DNA extraction a nondestructive method was used. DNA sequences were compared to Korean haplotype (AF106899) and Japanese haplotype (AF106897). All DNA sequences obtained from mite populations sampled in Argentina, share 98% of similitude with Korean Haplotype (AF106899). Taking into account these results, we are able to conclude that Korean haplotype is cosmopolite in Argentina.

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Uruguay is characterized by having an Africanization gradient in its honey bee (Apis mellifera) populations from areas bordering Brazil to the most remote locations. Morphological differences have also been found among Varroa destructor populations from different regions. A possible explanation for these morphological changes in mites could be explained by morphological correlations in the host/parasite A. mellifera/V. destructor system. The objective of the present study was to identify A. mellifera ecotypes in Uruguay and their correlation with V. destructor populations, using geometric morphometrics analysis. The hypothesis states that there is an Africanization gradient of A. mellifera in the northsoutheastern direction in Uruguay that correlates with morphological variations in V. destructor populations. A morphometrics analysis of six honey bee populations and their respective phoretic mites was carried out by sampling zones that show the gradient in the Uruguayan region. The main results obtained were a morphometric correlation between honey bees and mites. The use of landmarks could be adjusted for the intraspecific differentiation of V. destructor populations, which had not been considered previously. These studies are of major importance to further understand the parasitism caused by V. destructor in honey bees.Correlacio ´n morfome ´trica entre morfotipos de Apis mellifera (Hymenoptera) y Varroa destructor (Acari) en Uruguay Uruguay se caracteriza por tener un gradiente de africanizacio ´n en sus poblaciones de abeja de la miel (Apis mellifera), desde las a ´reas que bordean Brasil hasta las regiones ma ´s remotas. Estas diferencias morfolo ´gicas tambie ´n han sido encontradas en las poblaciones de Varroa destructor en diferentes regiones. Una explicacio ´n posible para estos cambios morfolo ´gicos en los a ´caros podrı ´a ser explicada por la correlacio ´n morfolo ´gica entre hospedador y para ´sito, A. mellifera y V. destructor. El objetivo del presente estudio es identificar los ecotipos de A. mellifera en Uruguay y su correlacio ´n con las poblaciones de V. destructor usando ana ´lisis de morfometrı ´a geome ´trica. Nuestra hipo ´tesis de partida es que hay un gradiente de africanizacio ´n en A. mellifera en direccio ´n norte-sureste en Uruguay y que se correlaciona con variaciones morfolo ´gicas en las poblaciones de V. destructor. Un ana ´lisis morfome ´trico de seis poblaciones de abeja de la miel y sus respectivos a ´caros fo ´reticos fue llevado a cabo muestreando en zonas de la regio ´n uruguaya en las que se apreciaba el gradiente. Como resultado principal se obtuvo una correlacio ´n morfome ´trica entre abejas y a ´caros. El uso de landmarks puede ser ajustado para la diferenciacio ´n intraespecı ´fica de las poblaciones de V. destructor, lo que no habı ´a sido considerado previamente. Estos estudios son de gran importancia para entender el parasitismo causado por V. destructor en las abejas.