Lilia I. de Guzman

Breeding for resistance to Varroa destructor in North America

Breeding for resistance to Varroa destructor in North America provides the long-term solution to the economic troubles the mite brings. This review reports the development of two breeding successes that have produced honey bees of commercial quality that do not require pesticide treatment to control Varroa, highlights other traits that could be combined to increase resistance and examines the potential uses of marker-assisted selection (MAS) for breeding for Varroa resistance. Breeding work continues with these stocks to enhance their commercial utility. This work requires knowledge of the mechanisms of resistance that can be further developed or improved in selected stocks and studied with molecular techniques as a prelude to MAS.ZusammenfassungDie Zucht auf Resistenz gegen Varroa destructor in Nordamerika bietet die langfristige Lösung für die von der Milbe verursachten wirtschaftlichen Schwierigkeiten. Dieses Review untersucht mehrere potenzielle Mechanismen der Resistenz gegen Varroa und berichtet über die Entwicklung von zwei Zuchterfolgen, aus denen Bienen von wirtschaftlicher Qualität hervorgegangen sind, die weniger Pestizidbehandlungen gegen Varroa benötigen als unselektierte Bienen.Das VSH Zuchtprogramm konzentriert sich auf die Selektion eines spezifischen Resistenzmechanismus, der Varroasensitive Hygiene genannt wird. Das Merkmal VSH wird über den Verkauf von VSH Königinnen, die mit Drohnen bereits vorhandener kommerzieller Linien gepaart wurden, für die Imker verfügbar gemacht. Die größte Resistenz kommt zwar in reinen VSH-Linien vor, die nachhaltigste Verbreitung wird jedoch durch VSH Hybridvölker erzielt. Durch das Auskreuzen reiner VSH Linien mit einer Vielzahl anderer kommerzieller Linien kann die genetische Diversität der Bienenpopulation in den USA auf relativ hohem Niveau gehalten werden. Reine VSH Zuchtköniginnen werden von Glenn Apiaries produziert und an kommerzielle Produzenten von Königinnen verkauft, die ihrerseits ausgekreuzte VSH Königinnen an Imker verkaufen.Das Programm zur Russischen Biene nutzt ein Zuchtschema, das auf einer geschlossenen Population basiert, um gegen Varroa resistente Linien zu verbreiten, die ursprünglich aus dem fernöstlichen Russland stammten. Die Russischen Honigbienen (RHB) des ARS wurden aus 18 importierten Linien durch Geschwistertests über mehrere Jahre hinweg entwickelt. Ihre Varroaresistenz geht auf mehrere Mechanismen zurück, zu denen gegenseitiges Putzen, varroasensitive Hygiene und für die Milbe geringe Attraktivität der Brut gehören. RHB Linien wurden gleichzeitig für Varroaresistenz, gute Honigproduktion und Resistenz gegen Tracheenmilben, Acarapis woodi, selektiert. Die Resistenz gegen Tracheenmilben trägt zu ihrer ausgezeichneten Überwinterungsfähigkeit bei. Der Erfolg der experimentellen RHB Selektion regte eine große kommerzielle Nachfrage an, und RHB werden zurzeit von einer als Russian Queen Breeder’s Association bekannten Züchterkooperative gezüchtet, vermehrt und an die Imker in den USA verbreitet.Die Zucht auf Varroaresistenz wird in der Zukunft wahrscheinlich auch markergestützte Selektion (MAS) mit einbeziehen, in welcher entweder die Expression von mit Resistenz verbundenen Genen (RNA) oder molekulare Marker, die mit Resistenzgenen in Verbindung stehen (DNA), benutzt werden um die Zuchteltern auszuwählen. Das endgültige Ziel ist, die arbeits- und zeitaufwändige Selektion im Feld durch eine Labordiagnose zu ersetzen. Es wird erwartet, dass MAS den Selektionsfortschritt sowohl für Resistenzmerkmale, die schon entwickelt wurden, als auch für Merkmale, für die diese Entwicklung hin zu nutzbaren kommerziellen genetischen Linien noch aussteht, wie z.B. gegenseitiges Putzen und Entfernen von Milben, beschleunigen wird.

New Asian types of Varroa destructor: a potential new threat for world apiculture

The invasion of the Western honey bee, Apis mellifera, by Varroa destructor is attributed to two mitochondrial haplotypes (K and J) that shifted last century from their primary host the Eastern honey bee, A. cerana, in north-east Asia. Here, mitochondrial DNA sequences (cox1, cox3, atp6 and cytb: 2700 base pairs) were obtained from mites infesting both Eastern and Western honeybees (respectively 21 and 11 colonies) from Asia including regions where the shifts first occurred. A total of eighteen haplotypes were uncovered in Asia (11 on A. cerana and 7 on A. mellifera). Two new variants of the K haplotype and two of the J haplotype were found on Western honeybees in what appeared to be well-established infestations. New haplotypes may represent a potential threat to A. mellifera worldwide. The extreme lack of polymorphism in the K and J haplotypes outside of Asia, can now be plausibly explained as being due to genetic ‘bottlenecks’ that occurred in Asia before and after mites shifted from their original Eastern honeybee host.ZusammenfassungDie Varroamilbe, Varroa destructor, ist ein gut adaptierter Parasit der Östlichen Honigbiene (Apis cerana), insbesondere in den nördlichen Regionen des asiatischen Festlands. Mit ihrem Wechsel auf die Westliche Honigbiene (A. mellifera) im letzen Jahrhundert kam es zu einer dramatischen Ausbreitung dieser Milbe. Als verantwortlich für den Parasitenübergang werden zwei mitochondriale (mt) Haplotypen (K1 und J1) von Varroa angesehen. Bereits erhobene molekulare Daten deuten darauf hin, dass es sich hierbei, aufgrund der zeitlichen Zusammenhänge dieser Wirtswechsel, um zwei partiell isolierte Klone handelt. Mittels Genotypisierung von V. destructor Isolaten aus Regionen, in denen die Wirtswechsel der J1 und K1 Milben zuerst stattgefunden hatten, sowie einer weiträumigeren Untersuchung des natürlichen Ausbreitungsgebiets von V. destructor in Asien, versuchten wir in der vorliegenden Studie ein genaueres Bild über den Befall von A. mellifera durch V. destructor zu erhalten. Jede Milbenprobe wurde zunächst anhand des publizierten 458 Basenpaarfragments des mitochondrialen Gens Cytochromoxidase 1 (cox1) genetisch charakterisiert, um neue Varianten bereits bekannten Haplotypen zuordnen zu können. Um die genetische Variabilität der Milben besser erfassen zu können, wurde im nächsten Schritt ein 2700 Nukleotide langes Fragment sequenziert, das vier mitochondriale Gene beinhaltet: cox1, Cytochromoxidase III (cox3), ATP Synthase 6 (atp6) und Cytochrom b (cytb). Wir untersuchten Varroamilben aus Asien, die sowohl die Östliche (21 Völker) als auch die Westliche Honigbiene (11 Völker) befallen hatten (Tab. I). Milben mit identischer Sequenz des 458 Basenpaare (bp) langen cox1 Fragments wurden als Mitglieder jeweils einer der sieben Haplogruppen (K1, J1, V1, C1, C2, C3, L1) betrachtet. Insgesamt fanden wir 18 mt Haplotypen (Varianten der zusammenhängenden Sequenzen innerhalb einer Haplogruppe (Tab. III). Von diesen fanden wir 12 auf A. cerana und 6 auf A. mellifera (Tab. I, Abb. 1). Obwohl wir nur eine neue Haplogruppe fanden (C3 in Tab. I und III), konnten wir 12 neue Haplotypen innerhalb der Haplogruppen erkennen, für die bisher keine genetische Variation bekannt war. Dies zeigt, dass Varroamilben in Asien genetisch wesentlich variabler sind, als bisher angenommen. Unsere Untersuchung zeigt des weiteren, dass die weltweit auf A. mellifera gefundenden ursprünglichen K1 und J1 Haplotypen von V. destructor aus zwei unterschiedlichen Milbenpopulationen stammen. Diese sind jeweils durch die K1 und die J1 Haplogruppenzuordnung definiert (Abb. 2), die im nordöstlichen Asien A. cerana befallen. Beide Populationen sind genetisch wesentlich variabler, als bisher angenommen, und die hier neubeschriebenen Haplotypen dieser Populationen haben A. mellifera in Asien zwar befallen, sich aber noch außerhalb dieser Region verbreitet. Diese neuen Haplotypen stellen nun neue potentielle Bedrohungen für A. mellifera außerhalb Asiens dar. Außerdem stellen diese Beobachtungen eine Warnung gegen die freie Verfrachtung von Honigbienen dar und zeigen die Notwendigkeit einer strengen und korrekten Quarantäne für den internationalen Handel mit lebenden Honigbienen.

Time of drone flight in four honey bee species in south-eastern Thailand

SUMMARYAt Chanthaburi, Thailand, four species of Apis, A. andreniformis, A. florea, A. cerana and A. dorsata, are sympatric. Observations were carried out on three wild colonies of each species on various days in February 1992. The daily drone flight periods were only partially specific: A. andreniformis from 12.15 h to 13.45 h; A. florea from 14.00 h to 16.45 h; A. cerana from 15.15 h to 17.30 h; and A dorsata from 18.15 h to 18.45 h. The significance of these partially separate drone flight periods is discussed in terms of both reproductive isolation and evolution.

Temperature affects Aethina tumida (Coleoptera: Nitidulidae) Development

Summary The effects of temperature on several life history parameters of small hive beetles (SHB), Aethina tumida, were investigated under laboratory conditions. Our results showed that the development, body size and weight of SHB were dependent on temperature. Egg incubation was about two days at higher temperature (34°C) and three days at lower (room) temperature (24–28°C). Exposure of larvae to lower temperature resulted in a 15-day extension to their development to adult emergence with a mean of 36.31 ± 0.08 days as opposed to 20.68 ± 0.08 days at higher temperature (34°C). At lower temperature, the developmental time (first instar to adult emergence) of males was about one-half day longer (36.63 ±0.12 days) than that of females (36.02 ±0.15 days). Higher temperature supported larger (length = 6.30 ± 0.07mm, width = 3.48 ± 0.02mm) and heavier (12.95 ± 0.22mg) adult females than did the lower temperature (length = 5.30 ± 0.04mm, width = 3.39 ± 0.02mm, weight = 11.40 ± 0.20mg). Weight and width similarities between males exposed to higher temperature (weight = 11.53 ±0.14 mg, width = 3.43 ± 0.02mm) and females reared under room temperature (weight = 11.40 ± 0.20mg, width = 3.39 ± 0.02mm) were also observed. From this study, we can deduce that the abundance and impact of SHB on honey bee colonies may be influenced by their rate of development in different thermic regimes. A new technique for rearing individual SHB is also described.

Comparative nest architecture of the dwarf honey bees

SUMMARYComplete descriptions using a variety of measurements are provided for nests of Apis andreniformis from south-eastern Thailand, Sichuan and Hunan Provinces of China, and Palawan, Philippines and Apis florea from southeastern Thailand and Hunan Province of China. Overall, the single-comb nest of A. andreniformis has a very different structure from that of A. florea. The comb built by A. andreniformis has a midrib both above and below the supporting branch. However, the comb built by A. florea has a mid-rib only in the brood area below the supporting branch. The honey storage mid-rib of A. andreniformis nests gives them a characteristic crown appearance. Other differences include the overall size of the nest, the width and depth of worker cells and the width of drone cells.

Standard methods for tracheal mite research

Summary The honey bee tracheal mite (HBTM) Acarapis woodi (Rennie) (Acari: Tarsonemidae) is an obligate endoparasite of honey bees. First described from the Western (European) honey bee Apis mellifera L., this mite species was initially observed when honey bee colonies on the Isle of Wight, UK were dying between 1904 and 1919 (Rennie, 1921). Since then, this mite has been found in Europe, North and South America and parts of Asia, but its global distribution is not well understood. In this chapter, we outline protocols for collecting, detecting, identifying, diagnosing and measuring the infestation rates of A. woodi. We also describe methods to determine the damage threshold, outline several control measures, and describe methods for studying live mites.

Asynchronous Development of Honey Bee Host and Varroa destructor (Mesostigmata: Varroidae) Influences Reproductive Potential of Mites

ABSTRACT A high proportion of nonreproductive (NR) Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae), is commonly observed in honey bee colonies displaying the varroa sensitive hygienic trait (VSH). This study was conducted to determine the influence of brood removal and subsequent host reinvasion of varroa mites on mite reproduction. We collected foundress mites from stages of brood (newly sealed larvae, prepupae, white-eyed pupae, and pink-eyed pupae) and phoretic mites from adult bees. We then inoculated these mites into cells containing newly sealed larvae. Successful reproduction (foundress laid both a mature male and female) was low (13%) but most common in mites coming from sealed larvae. Unsuccessful reproductive attempts (foundress failed to produce both a mature male and female) were most common in mites from sealed larvae (22%) and prepupae (61%). Lack of any progeny was most common for mites from white-eyed (83%) and pink-eyed pupae (92%). We also collected foundress mites from sealed larvae and transferred them to cells containing newly sealed larvae, prepupae, white-eyed pupae, or pink-eyed pupae. Successful reproduction only occurred in the transfers to sealed larvae (26%). Unsuccessful reproductive attempts were most common in transfers to newly sealed larvae (40%) and to prepupae (25%). Unsuccessful attempts involved the production of immature progeny (60%), the production of only mature daughters (26%) or the production of only a mature male (14%). Generally, lack of progeny was not associated with mites having a lack of stored sperm. Our results suggest that mites exposed to the removal of prepupae or older brood due to hygiene are unlikely to produce viable mites if they invade new hosts soon after brood removal. Asynchrony between the reproductive status of reinvading mites and the developmental stage of their reinvasion hosts may be a primary cause of NR mites in hygienic colonies. Even if reinvading mites use hosts having the proper age for infestation, only a minority of them will reproduce.

Parasites, pathogens, and pests of honeybees in Asia

Asia is home to at least nine honeybee species, including the introduced Apis mellifera. In addition to A. mellifera and Apis cerana being widely employed for commercial beekeeping, the remaining nonmanaged species also have important ecological and economic roles on the continent. Species distributions of most honeybee species overlap in Southeast Asia. This promotes the potential for interspecific transmission of pests and parasites and their spread to other parts of the world by human translocation. The decline of honeybee populations is of great concern around the world, including in Asia. The global colony losses of A. mellifera are believed to be caused, in part, by parasites, pathogens, and pests originating from Asia, such as the mite Varroa destructor, the microsporidian Nosema ceranae, and some bee viruses. This review discusses important pests, pathogens, and parasites in both the introduced A. mellifera and native honeybees in Asia to provide an overall picture of honeybee health in the region and future threats to the apiculture industry.

Differential viral levels and immune gene expression in three stocks of Apis mellifera induced by different numbers of Varroa destructor

The viral levels and immune responses of Italian honey bees (IHB), Russian honey bees (RHB) and an outcross of Varroa Sensitive Hygienic bees (POL) deliberately infested with one or two foundress Varroa were compared. We found that the Deformed wing virus (DWV) level in IHB inoculated with one or two foundress Varroa increased to about 10(3) or 10(5) fold the levels of their uninfested brood. In contrast, POL (10(2) or 10(4) fold) and RHB (10(2) or l0(4) fold) supported a lower increase in DWV levels. The feeding of different stages of Varroa nymphs did not increase DWV levels of their pupal hosts. Analyses of their corresponding Varroa mites showed the same trends: two foundress Varroa yielded higher DWV levels than one foundress, and the addition of nymphs did not increase viral levels. Using the same pupae examined for the presence of viruses, 16 out of 24 genes evaluated showed significant differential mRNA expression levels among the three honey bee stocks. However, only four genes (Defensin, Dscam, PPOact and spaetzle), which were expressed at similar levels in uninfested pupae, were altered by the number of feeding foundress Varroa and levels of DWV regardless of stocks. This research provides the first evidence that immune response profiles of different honey bee stocks are induced by Varroa parasitism.

Functionality of Varroa-Resistant Honey Bees (Hymenoptera: Apidae) when used in Migratory Beekeeping for Crop Pollination

ABSTRACT Two types of honey bees, Apis mellifera L. (Hymenoptera: Apidae), bred for resistance to Varroa destructor Anderson & Trueman were evaluated for performance when used in migratory crop pollination. Colonies of Russian honey bees (RHB) and outcrossed bees with Varroa-sensitive hygiene (VSH) were managed without miticide treatments and compared with colonies of Italian honey bees that served as controls. Control colonies were managed as groups which either were treated twice each year against V. destructor (CT) or kept untreated (CU). Totals of 240 and 247 colonies were established initially for trials in 2008 and 2009, respectively. RHB and VSH colonies generally had adult and brood populations similar to those of the standard CT group regarding pollination requirements. For pollination of almonds [Prunus dulcis (Mill.) D.A.Webb] in February, percentages of colonies meeting the required six or more frames of adult bees were 57% (VSH), 56% (CT), 39% (RHB), and 34% (CU). RHB are known to have small colonies in early spring, but this can be overcome with appropriate feeding. For later pollination requirements in May to July, 94–100% of colonies in the four groups met pollination size requirements for apples (Malus domestica Borkh.), cranberries (Vaccinium macrocarpon Aiton), and lowbush blueberries (Vaccinium angustifolium Aiton). Infestations with V. destructor usually were lowest in CT colonies and tended to be lower in VSH colonies than in RHB and CU colonies. This study demonstrates that bees with the VSH trait and pure RHB offer alternatives for beekeepers to use for commercial crop pollination while reducing reliance on miticides. The high frequency of queen loss (only approximately one fourth of original queens survived each year) suggests that frequent requeening is necessary to maintain desired genetics.