Ethel M. Villalobos

Global Honey Bee Viral Landscape Altered by a Parasitic Mite

Honey Bees Beware of the Mite The emergence of a virulent form of a viral disease that has long been associated with the world-wide death of honey bees has occurred in the Hawaiian archipelago. Martin et al. (p. 1304) exploited this unique situation to study the mechanisms behind the emergence. Honey bee populations have long been established on the isolated Hawaiian Islands but only recently have some islands become infested with the Varroa mite. This mite has selected for a single viral pathogen-deformed wing virus among the honey bee population, with the appearance of a single dominant virus strain, which has now spread worldwide. Thus, a normally benign viral pathogen has become one of the most widely distributed and contagious insect viruses on the planet. The arrival on Hawaii of the mite Varroa has decreased diversity and increased prevalence of deformed wing virus. Emerging diseases are among the greatest threats to honey bees. Unfortunately, where and when an emerging disease will appear are almost impossible to predict. The arrival of the parasitic Varroa mite into the Hawaiian honey bee population allowed us to investigate changes in the prevalence, load, and strain diversity of honey bee viruses. The mite increased the prevalence of a single viral species, deformed wing virus (DWV), from ~10 to 100% within honey bee populations, which was accompanied by a millionfold increase in viral titer and a massive reduction in DWV diversity, leading to the predominance of a single DWV strain. Therefore, the global spread of Varroa has selected DWV variants that have emerged to allow it to become one of the most widely distributed and contagious insect viruses on the planet.

Cue Lure and the Mating Behavior of Male Melon Flies (Diptera: Tephritidae)

Laboratory tests were conducted to assess the effect of the parapheromone cue lure on the mating behavior of male Bactrocera cucurbitae (Coquillett). Exposure to cue lure resulted in a short-term mating advantage. For wild flies, treated males that fed on cue lure on the day of testing, or 1 day prior to testing, mated more frequently than control males that had no prior exposure to cue lure. However, control and treated males had similar mating success in tests performed 3 or 7 days after the treated males were exposed to the lure. Exposure to cue lure also increased the mating success of mass-reared, irradiated males relative to unexposed wild males, though this advantage was evident for only 1 day following exposure. Cue lure appeared to enhance mating performance by increasing male wing-fanning activity but not the attractiveness of the signal per se. A field study revealed that irradiated males exposed to cue lure 1 week prior to release were less likely to be captured (in Steiner traps baited with cue lure and naled) than unexposed males. These findings suggest that exposure of sterile males to cue lure might improve the effectiveness of sterile insect release as well as enable simultaneous control programs of sterile insect release and male annihilation.

Effects of Diet, Ginger Root Oil, and Elevation on the Mating Competitiveness of Male Mediterranean Fruit Flies (Diptera: Tephritidae) from a Mass-Reared, Genetic Sexing Strain in Guatemala

The release of sterile males is a key component of an areawide program to eradicate the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), from Guatemala and southern Mexico. The objective of our study was to assess the effects of adult diet, exposure to ginger root oil (Zingiber officinale Roscoe), and elevation on the mating competitiveness of the sterile males used in an areawide program. Sterile males were maintained on a protein-sugar (protein-fed) or a sugar-only (protein-deprived) diet and were exposed (for 4 h 1 d before testing) or not exposed to ginger root oil. In field-cage trials conducted at a high (1,500 m) and low (700 m) site, we monitored the influence of these treatments on the mating success of sterile males in competition with wild males (reared exclusively on the protein-sugar diet and without ginger root oil exposure) for wild females. Elevation and ginger root oil exposure had significant effects, with sterile males having higher mating success at the low-elevation site and ginger root oil-exposed males having greater success than ginger root oil-deprived males at both sites. Diet did not have a significant overall effect, and its influence varied with elevation (dietary protein seemed to provide an advantage at the high-elevation site but not at the low-elevation site). Possible implications of these findings for eradication programs against the Mediterranean fruit fly are discussed.

Do the honeybee pathogens Nosema ceranae and deformed wing virus act synergistically

The honeybee pathogens Nosema ceranae and deformed wing virus (DWV) cause the collapse of honeybee colonies. Therefore, it is plausible that these two pathogens act synergistically to increase colony losses, since N. ceranae causes damage to the mid-gut epithelial ventricular cells and actively suppresses the honeybees’ immune response, either of which could increase the virulence of viral pathogens within the bee. To test this hypothesis we exploited 322 Hawaiian honeybee colonies for which DWV prevalence and load is known. We determined via PCR that N. ceranae was present in 89–95% of these colonies, with no Nosema apis being detected. We found no significant difference in spore counts in colonies infected with DWV and those in which DWV was not detected, either on any of the four islands or across the entire honeybee population. Furthermore, no significant correlation between DWV loads (ΔCT levels) and N. ceranae spore counts was found, so these two pathogens are not acting synergistically. Although the Hawaiian honeybees have the highest known prevalence of N. ceranae in the world, with average number of spores been 2.7 million per bee, no acute Nosema related problems i.e. large-scale colony deaths, have been reported by Hawaiian beekeepers.

Buzzing Bees (Hymenoptera: Apidae, Halictidae) on Solanum (Solanaceae): Floral Choice and Handling Time Track Pollen Availability

Flower selection and pollen-collecting effort were monitored for 3 species of bees that sonicate flowers of Solanum wendlandii Hook. for pollen in southern Costa Rica. Between 0700-0900 hours, Bombus pullatus (Fkln.), Euglossa erythrochlora Moure, and Pseudaugochloropsis graminea (Fabricius) foraged more frequently at new flowers (that had opened the day of observation) than old ones (that had opened at least 1 day before observation). Between 0900-1100 hours, however, this preference was no longer evident, and all 3 species visited new and old flowers with similar frequency. E. erythrochlora and P. graminea spent more time harvesting pollen during 1) initial (first or second) visits to new flowers than initial visits to old flowers and 2) initial visits to new flowers than final (seventh or later) visits to new flowers. Similar, although not statistically significant, trends were evident for B. pullatus as well. An experiment using pollinator exclusion bags revealed that the reduced foraging effort at individual flowers was resource-dependent and was not simply a time-dependent phenomenon.

Moku virus; a new Iflavirus found in wasps, honey bees and Varroa.

There is an increasing global trend of emerging infectious diseases (EIDs) affecting a wide range of species, including honey bees. The global epidemic of the single stranded RNA Deformed wing virus (DWV), driven by the spread of Varroa destructor has been well documented. However, DWV is just one of many insect RNA viruses which infect a wide range of hosts. Here we report the full genome sequence of a novel Iflavirus named Moku virus (MV), discovered in the social wasp Vespula pensylvanica collected in Hawaii. The novel genome is 10,056 nucleotides long and encodes a polyprotein of 3050 amino acids. Phylogenetic analysis showed that MV is most closely related to Slow bee paralysis virus (SBPV), which is highly virulent in honey bees but rarely detected. Worryingly, MV sequences were also detected in honey bees and Varroa from the same location, suggesting that MV can also infect other hymenopteran and Acari hosts.

Temporal and Spatial Variation in the foraging Behavior of Honey Bees (Hymenoptera: Apidae) at Chinese Violets

This study describes temporal and spatial variation in the foraging behavior of honey bees, Apis mellifera L., at the Chinese violet, Asystasia gangetica (L.) T. Anderson, in Hawaii. Workers made 3 types of visits: “out” (O-) visits involving nectar robbing through corollar slits made by carpenter bees (Xylocopa sonorina (Smith), “in-upright” (IR-) visits involving upright entry along the base of the corolla, and “in-upside down” (ID-) visits involving spiral, upside-down entry along the top of the corolla. In general, individual workers displayed only 1 tactic over 10 successive flower visits and over successive days. Nectar-robbing workers visited more flowers per min but spent less time per flower than workers making IR- or ID-visits. Bees making O- or IR-visits carried similar nectar loads but only very small amounts of pollen, whereas the reverse was true for bees making ID-visits. O- and IR-visits were made throughout the day, but ID-visits were observed only in the morning. Based on inter-site comparisons, the incidence of nectar robbing was influenced by the local density of carpenter bees which made the perforations used by nectar robbing honey bee workers.

The mite that jumped, the bee that traveled, the disease that followed

Global expansion and trade contributed to the declining health of honeybees [Also see Report by Wilfert et al.] European honeybees are among the best-studied and most widely recognized insect species in the world. Originally kept for honey production, they have become the flagship species for pollination and large-scale agriculture. Since large colony losses were reported across the United States in 2006, researchers have investigated the myriad factors that contribute to the decline in honeybee populations. In particular, the aptly named Varroa destructor mite (see the photo) and the deformed wing virus (DWV) have been clearly linked to colony collapse (1). On page 594 of this issue, Wilfert et al. use a phylogeographic analysis to examine the evolutionary origin and mechanisms for the global spread of the DWV (2).

Varroa destructor resistance of honey bees in Hawaii, USA, with different genetic proportions of Varroa Sensitive Hygiene (VSH)

Apis mellifera, Varroa destructor, honey bees, genetic resistance, integrated pest management, bee breeding Journal of Apicultural Research 51(3): 288-290 (2012)

Research Reports: Observations on the Mating Behavior of Male Stictia Heros (Hymenoptera: Sphecidae)

Males of the neotropical sand wasp Stictia heros (Fabr.) displayed territorial behavior in female nesting areas, presumably to gain access to newly eclosed virgin females. Males hovered above a fixed point of the beach and defended small areas (1 m@^2) with rapid flights at all intruders. Observations of marked individuals revealed that males defend the same site for at least several days. Unlike head and abdominal temperatures, the thoracic temperature of males varied independently of ambient temperature, indicating active thermoregulation of the flight muscles. Differences between our results and those of Larson (1989) are discussed.