Martín Javier Eguaras

Varroa destructor is one of the biggest threats to honey bee populations worldwide. Three classes of disparately acting acaricidal compounds are currently used to combat infestations: the pyrethroid insecticides, fluvalinate and flumethrin; the organophospate, coumaphos; and the formamidine, amitraz. Unfortunately, these compounds tend to persist in both honey and wax compromising honey bee health and contaminating hive products used by humans. In addition, overuse of synthetic compounds encourages the emergence of acaricide resistance in V. destructor. Current evidence suggests that resistance to pyrethroid insecticides in V. destructor initially arose in Italy during a four-year period of heavy pyrethroid application. After that, several cases of resistant populations have been reported around the world. More data is needed to track the origin and dispersal of mites resistant to the organophosphate coumaphos, and formamidine amitraz. Little is known about the genetic procedures leading to fixation of acaricide resistance genes, which can vary depending on mite genetics, environmental conditions, and beekeeping management. This review highlights the main aspects associated with the development of acaricide resistance and alternative strategies are suggested to deal with this problematic.

This study aimed to detect mutations associated with pyrethroid resistance mechanism in different populations of Varroa destructor from Uruguay and Argentina with different degree of susceptibility to this family of acaricides. Bioassays were performed to evaluate the degree of susceptibility to flumethrin and tau-fuvalinate; then mites were studied in order to determine the presence or absence of the resistance-associated mutations by sequencing a region of the sodium channel gene. In the mites studied from Colonia, which showed resistance to flumethrin and susceptibility to tau-fluvalinate in the bioassays, L925V mutation was observed in heterozygous and homozygous state. The presence of the wild-type allele in homozygous state was identified in all mites from Treinta y Tres, in which acaricides have never been used. The mite population from Mar del Plata through bioassays were determined as susceptible to both pyrethroids, however, genotyping results showed the presence of heterozygous individuals (925 V/L) as well as homozygous wild type (925L), while homozygous resistant individuals (925V) were present at low frequency. This would suggest that this population presents a great potential to give a generalized resistance to pyrethroids. This study represents the first report of a L925V mutation in resistant mites to flumethrin from South America.

European honey bees (Apis mellifera) are highly social insects that live in colonies (Pennisi, 2006; Winston, 1987); they are very important for agriculture, fulfilling an important role in pollina...

Aluen Cap is an oxalic acid (OA) formulation that shows promise as a control method for Varroa destructor. This work explores the use and efficacy of Aluen Cap against V. destructor in Africanized honeybees in Veracruz Mexico, where capped brood is always present across the year and acaricide resistance was a problem. Twenty-four beehives were assessed over 42 days, a period of time associated with the liberation of OA from Aluen Cap. The acaricide formulation shows significantly higher mean efficacy (92.1%) than control hives (36.5%). This test suggests the high value of the new oxalic acid formulation in AHBs despite the high temperatures and presence of brood, avoiding the necessity of multiple applications of OA, hence simplifying colony management.

The effects of parasites, pathogens and agrochemical exposure combined with the cold temperatures of winter in temperate-climate regions contribute to the immunosuppression of honey bees. Recently, we demonstrated that abscisic acid (ABA) dietary supplementation increased the tolerance of Apis mellifera brood to low temperatures. Here, we study the relationship between cold exposure, dietary ABA supplementation, and the expression of genes involved in the immune response of in-vitro-reared bee larvae. We found that cold exposure induced the expression of several immune-associated genes in honey bee larvae, supporting that the immune system is active during the cold stress response in A. mellifera. At the same time, the ingestion of ABA alone increased the expression levels of the Toll pathway receptor toll18W and nitric oxide synthase (nos) genes, which were induced also by low temperatures, reinforcing the connection between honey bees’ response to cold stress and ABA.

(2019). Biotic Stressors Affecting Key Apiaries in Argentina. Bee World. Ahead of Print.

Although many honey bee RNA viruses have been correlated with colony declines, little is known regarding the potential role of DNA viruses. Apis mellifera filamentous virus (AmFV) is a large double stranded DNA virus of honey bees and its prevalence and relationship with other parasites is poorly known. In the present work, we have described a high prevalence of AmFV in Argentinian apiaries, and a retrospective survey of archived honey bee samples revealed that AmFV has been present in Argentina since at least 2006. This is the first report involving AmFV in South America.

African honey bee subspecies Apis mellifera scutellata began to spread in the American continent from southern Brazil in 1956. The process of Africanization involved both maternal and paternal bidirectional gene flow between European and Africanized honey bees. In Argentina, Africanized honey bees dominate in the northern semitropical regions and a hybrid area is defined between (ca. 32°–34°latitude). Although previous analysis has been carried out in Buenos Aires province, no analysis has been made south of this latitude. We used mitochondrial DNA (mtDNA) assays and wing geometric morphometrics to determine the prevalence of Africanized honey bees in managed populations. African mitotype origin and subspecies identity, were determined at three regions from Argentina. In our study, we analyzed 480 samples by wing morphometry and 157 by cytochrome-b assays, collected during 2013–2016. Our results show that North of 35°N latitude, honey bees with African mitotype were quite common (88.64%) finding high similarity with A. m. scutellata. South of that latitude, in temperate regions, we found African mitotype in only 18 of 133 colonies analyzed and a mixture of both European (A. m. ligustica, A. m. cárnica, A. m. mellifera) and African subspecies, most likely derived from North African honey bee (A. m. intermissa). Our results confirmed the existence of Africanized honey bee populations with a gradual cline from north to south, as a result from recent A. m. scutellata-derived bee expansion. Beyond the transition area between the 30°–35°S parallels bees carrying the European mitotype were fairly common.