Showing papers on "Varroa sensitive hygiene published in 2002"

Parasitism in the social bee Apis mellifera: quantifying costs and benefits of behavioral resistance to Varroa destructor mites

Abstract: The case of a host-parasite relationship may provide a good model to evaluate the costs and bene- fits of some behaviors, an area in which field data a currently lacking. European (EHB) and Africanized (AHB) honey bees are two Apis mellifera subspecies that coexist in Mexico, the former highly compatible with Varroa destructor, the latter less compatible. Here we examine two mechanisms that could explain the low compatibility between AHB and V. destructor in Mexico: (1) grooming behavior appeared significantly more intensive in AHB colonies, but was nevertheless ineffective; (2) EHB removed 8.03% of the infested brood, while AHB removed 32.46%, especially between 5 and 7 days post-capping. Though the cost of re- moving infested brood was not different between subspecies, the result, in terms of the amount of removed in- fested brood, was significantly higher for AHB. For both bees, there is thus a real cost, since removing a pupa results in a lower number of adult bees. We discuss the possibility that the removal of infested brood corre- sponds with a threshold above which the cost of removal becomes greater than the benefit. Apis mellifera / Varroa destructor / parasitology / costs and benefits / behavioral resistance

Reproduction of Varroa destructor in South African honey bees: does cell space influence Varroa male survivorship?

Abstract: The ability of Varroa destructor to reproduce in the African honey bee Apis mellifera scutellata was studied. In addition, the effects of space within the brood cell and short brood developmental time on mite reproduction, was investigated using A. m. scutellata cells parasitised by a A. m. capensis worker pseudo-clone. In A. m. scutellata worker cells Varroa produced 0.9 fertilised females per mother mite which is the same as found in susceptible European honey bees, but greater than the 0.4 produced in cells containing the pseudo-clone. Low mite reproductive success in cells containing pseudo-clone was mainly as a result of increased mite mortality. This was caused by male protonymphs and some mothers becoming trapped in the upper part of the cell due to the pseudo-clone being 8% larger than their host and not due to their short developmental time. Therefore, mite populations in South African A. m, scutellata and A. m. capensis honey bees are expected to increase to levels observed in Europe and USA.

Cuticular volatiles, attractivity of worker larvae and invasion of brood cells by Varroa mites. A comparison of Africanized and European honey bees.

Abstract: Africanized honey bees (AHBs) of Brazil and Mexico have proven to be tolerant to Varroa destructor mites. In contrast, European honey bees (EHBs: Apis mellifera carnica) at the same tropical study site are highly intolerant to these ectoparasites. A lower attractiveness of Varroa-tolerant AHB larvae has been hypothesised to be an important trait in reducing the susceptibitlity of AHBs to these mites. Thus, selection for EHB brood that is less attractive to mites is thought to be one possibility for limiting mite population growth and thus increase the tolerance of EHBs to the mite.¶In Ribeirao Preto, Brazil, European A. m. carnica bees and AHBs were tested with respect to their rate of brood infestation and brood attractiveness to Varroa mites. For the comparison of brood infestation rates, we introduced combs with pieces of EHB and AHB brood into honey bee colonies (18 repetitions). The relative infestation rate of EHB brood was significantly higher compared to AHB brood.¶The preference behaviour of single Varroa mites was tested in a laboratory bioassay where either living host stages were offered or host extracts were presented on dummies. By these tests we could confirm the preference of Varroa females for certain developmental host stages and for their corresponding extracts. In contrast to the within-colony results, Varroa mites in the laboratory bioassay showed a slight preference for AHB compared to EHB larvae.¶The gas chromatographic analysis revealed differences in the chemical spectrum of extracts obtained from different larvae. In accord with the results of the bioassays, we could detect stage-specific odour differences in larval cuticular compounds, including methyl esters and hydrocarbons that have been described as kairomones. None of these substances, however, revealed significant race-specific differences. Therefore, the quantity and composition of certain cuticular compounds seem to be responsible only for the recognition of a suitable host stage by Varroa females. The different infestation rates in the colonies, however, seem to be caused neither by race-specific differences in attractiveness of bee larvae nor by an extended attractive period of EHB larvae: both AHB and EHB larvae become attractive approximately 21 h before capping of the brood cell, and thus have the same window of time when they can be parasitised.¶Therefore differential Varroa-infestation rates are not related to larval attraction but probably are determined by other race-specific and colony-related factors.

Varroa destructor infestation impact on Apis mellifera carnica capped worker brood production, bee population and honey storage in a Mediterranean climate

Abstract: This study investigated the impact of Varroa destructor infestation on the amount of capped worker brood, the adult bee population and honey production of authenticated Apis mellifera carnica colonies kept in a Mediterranean climate. For this purpose, colonies were set-up and either maintained mite-free or artificially mite-infested and allowed to develop an infestation. Periodical evaluations of those colonies unravelled the pattern of the previously mentioned variables across the season, and allowed for comparative numerical analyses. Progressive reductions on the amount of capped worker brood, bee population and honey storage in mite-infested colonies only became in- creasingly evident during spring and summer, apparently associated with impressive mite population increases. By the end of the experiment, mite-infested colonies showed a unitary average reduction of 45% in the amount of capped honey they stored, meaning an average annual loss of < 24 kg of honey per colony. However, the amount of capped honey stored per bee and day was found to be independent from colony V. destructorstatus, indicating a lack of direct effect of mite infestation on honey hoard- ing behaviour. Varroa destructor / Apis mellifera /population dynamics / honey production

Varroa-tolerant Italian honey bees introduced from Brazil were not more efficient in defending themselves against the mite Varroa destructor than Carniolan bees in Germany.

Abstract: In Europe and North America honey bees cannot be kept without chemical treatments against Varroa destructor. Nevertheless, in Brazil an isolated population of Italian honey bees has been kept on an island since 1984 without treatment against this mite. The infestation rates in these colonies have decreased over the years. We looked for possible varroa-tolerance factors in six Italian honey bee colonies prepared with queens from this Brazilian island population, compared to six Carniolan colonies, both tested at the same site in Germany. One such factor was the percentage of damaged mites in the colony debris, which has been reported as an indicator of colony tolerance to varroa. A mean of 35.8% of the varroa mites collected from the bottoms of the Italian bee colonies were found damaged, among which 19.1% were still alive. A significantly greater proportion of damaged mites were found in the Carniolan bees (42.3%) and 22.5% were collected alive. The most frequent kind of damage found was damaged legs alone, affecting 47.4% of the mites collected from debris in Italian bees, which was similar to the amount found in Carniolan colonies (46%). The mean infestation rate by the varroa mite in the worker brood cells in the Italian bee colonies was 3.9% in June and 3.5% in July, and in drone brood cells it was 19.3% in June. In the Carniolan honey bee colonies the mean infestation rates in worker brood cells were 3.0 and 6.7%, respectively in the months of June and July and 19.7% in drone brood cells in June. In conclusion, the 'Varroa-tolerant' Italian honey bees introduced from Brazil produced lower percentages of damaged mites (Varroa destructor) in hive debris and had similar brood infestation rates when compared to 'susceptible' Carniolan bees in Germany. In spite of the apparent adaptation of this population of Italian bees in Brazil, we found no indication of superiority of these bees when we examined the proportions of damaged mites and the varroa-infestation rates, compared to Carniloan bees kept in the same apiary in Germany.

Effect of some characters on the population growth of mite Varroa jacobsoni in Apis mellifera L colonies and results of a bi‐directional selection

Abstract: Two lines of honey bees (Apis mellifera ligustica) were selectively propagated by instrumental insemination using the population growth of the Varroa mite as a criteria. Different infestation rates are at least partially genetic since selection produced significant bi-directional differences between lines over a period of three subsequent generations. There was no correlation between several behavioural and physiological characteristics which are potentially associated with Varroa resistance (hygienic behaviour, physical damage to mites, infertility of the intruding mites) and the development of the Varroa population after artificial infestation. There was a positive significant correlation between the total mites in the colonies and the amount of reared brood. Colony infestation was also positively correlated with the amount of honey harvested.

Effect of acaricide resistance on reproductive ability of the honey bee mite Varroa destructor.

Abstract: The reproduction of pyrethroid-resistant Varroa destructor mite, a brood parasite of honey bees, was observed in Weslaco, Texas, and the results compared with known susceptible mite populations from other studies. Seven Apis mellifera colonies that had mite populations resistant to the acaricide Apistan™ were used. Pyrethroid-resistance was confirmed when only 17% rather than 90% of mites confined in dishes containing Apistan™ died after 12 h of exposure. The average number of eggs laid by resistant mites invading worker and drone cells was 4.4 and 5.4 respectively. This is similar to the number of eggs laid by susceptible mites in worker (4.4–4.8) or drone (4.7–5.5) cells. Also the average number of fertilised V. destructor female mites produced by resistant mites in worker (1.0) and drone (2.1) cells were similar to the number produced by susceptible mites in worker (0.9) and drone (1.9–2.2) cells. In addition, no major differences between the resistant and susceptible mite populations were observed in either worker or drone cells when six different reproductive categories and offspring mortality rates were compared. Therefore, it appears that there is little or no reproductive fitness cost associated with pyrethroid resistance in V. destructor in Texas.

Modeling the Efficiency of Sampling and Trapping Varroa destructor in the Drone Brood of Honey bees (Apis mellifera)

Abstract: A computer model simulating varroa mite (Varroa destructor— previously known as Varroa jacobsoni) infestation in colonies of honey bees (Apis mellifera) confirmed that, due to the preference of mites to invade drone (male) honey bee brood to reproduce, a very high proportion of the mite reproduction could occur in a relatively small amount of drone brood. Several regimes of sampling or removing drone bee pupae to estimate or remove numbers of varroa mites were simulated to compare their effectiveness. The model indicated that regular sampling of at least 100 drone pupae could provide the beekeeper with a useful warning of when numbers of varroa were approaching damaging levels. An infestation level of 15% of drone pupae would be a conservative threshold to indicate treatment was imminently required. The model indicated that significant reduction of mite numbers could be achieved either by very regular uncapping and removal of most of the natural drone pupae, or by trapping mites in artificially high numbers of drone pupae. The numbers of drone pupae required to significantly delay the mite build-up could be reduced considerably by trapping at a time when the bee colony was otherwise broodless. However, the varroa numbers were not controlled sufficiently by drone brood removal alone in any of the regimes tested.

MORTALITY OF Varroa destructor IN BROODLESS AFRICANIZED AND CARNICA HONEY BEE (Apis mellifera L.) COLONIES

Abstract: Varroa destructor infestation varies with climate conditions and race of Apis mellifera bees. Africanized bees show greater tolerance to varroa compared to...

Can the frequency of reduced Varroa destructor fecundity in honey bee (Apis mellifera) pupae be increased by selection

Abstract: Crosses were made between queens and drones from 16 different commercial sources of Euro- pean honeybees to determine if reproductive rates for Varroa destructor differed. Worker brood from four dif- ferent crosses averaged 4.2 mites per cell and were chosen as the high mite reproduction group. Four others averaged 2.4 mites per cell and were chosen for the low mite reproduction group. A second set of crosses within the high and low mite reproduction groups were made and the worker offspring tested for differences in mite fecundity. Worker brood of the high and low mite reproduction lines did not differ significantly in the average number of mites per cell. The proportion of infested cells with non-reproductive mites also was not affected by selection. These results suggest that the frequency of larval or pupal characteristics that we mea- sured in worker honeybees that might influence mite reproductive rates cannot be increased by selection based on average mite fecundity. Varroa destructor / Apis mellifera / genetic crosses / selection / mite fecundity

Virus succession in honeybee colonies infested with varroa destructor

Abstract: Introduction. When Varroa destructor nov. sp. (Anderson & Trueman, 2000) was first discovered in Europe in the 1970s, it was rapidly found to be a devastating pest of Apis mellifera. It was soon apparent however that the damage to colonies was not solely related to the size of the mite population. It was therefore suggested that secondary infections by other pathogens might explain the observed variation in the effect of mite parasitism. Work in Germany and elsewhere on mainland Europe in the early 1980s (Ball, 1985; Ball & Allen, 1988) showed that the primary cause of mortality in severely infested colonies was acute paralysis virus (APV), a virus never previously known to cause mortality in nature (Bailey & Ball, 1991; Ball & Bailey, 1997). Further work demonstrated that the mite could act as a vector of a number of honey bee viruses (Ball, 1989), and led to the discovery of a previously undescribed virus, deformed wing virus (DWV) in infested colonies (Bailey & Ball, 1991; Ball & Bailey, 1997).

A scientific note on the distribution of Africanized honey bees and Varroa destructor in feral honey bee populations in California

Abstract: A scientific note on the distribution of Africanized honey bees and Varroa destructor in feral honey bee populations in California Walter M. BOYCE*, Esther S. RUBIN, Chantal S. O’BRIEN a Department of Veterinary Pathology, Microbiology, and Immunology, School of Veterinary Medicine, One Shields Avenue, University of California, Davis, California, 95616, USA b Center for Reproduction of Endangered Species, Zoological Society of San Diego, PO Box 120551, San Diego, CA 92112-0551, USA c Research Branch, Arizona Game and Fish Department, 2221 W. Greenway Road, Phoenix AZ, 85023, USA

Effect of flumethrine on Varroa destructor in honeybee colonies.

Abstract: chemotherapy, flumethrine. The apiculture is an important factor in the Algerian agricultural development, in particular in the crossing pollination of numerous plants, cultivated or natural, and in the honey production. Installation of honeybee colonies increases and improves the plant production, but is also indispensable to the maintenance of the natural balance on earth. Honeybee constitutes a very important ecological index of the environment. But like all animals, honeybee can be affected by various diseases. One of the main illnesses that provoke big losses in apiculture in Algeria is varrosis (1). The etiologic factor is a parasitic mite

Varroa - bee relationships - what they tell us about controlling varroa mites on the european honeybee

Abstract: Until recently, only three species of Varroa mites had been recorded: Varroa jacobsoni, V. underwoodi and V. rindereri. Of these, V. jacobsoni had received the most attention from researchers, primarily because it was believed to have switched host from the Asian bee (Apis cerana) to the European honey bee (A. mellifera) some 40-50 years ago, then spread to become a serious parasite of A. mellifera worldwide. However, a little over a year ago, mites that had long been referred to as V. jacobsoni were found to be a complex of at least 2, but possibly 5, sibling species. These recent findings, together with others on bee taxonomy and Varroa reproductive behaviour on A. cerana and A. mellifera in Asia, have radically changed our understanding of Varroa/bee relationships. In this paper I briefly summarise these findings, before discussing what they tell us about controlling Varroa mites on A. mellifera worldwide.

Impact of varroa destructor on the honeybees of south africa

Abstract: The destructive mite Varroa destructor was first found in the Cape region of South Africa by P. KRYGER in August 1997. By 2000 it had spread from the Cape region occupied by Apis mellifera capensis bees to the highveld regions around Pretoria and southern end of the Kruger National Park, both regions occupied by A.m. scutellata bees. There has been much speculation about the impact of Varroa in South Africa for two reasons: 1.) It has been shown that the rapid development of the sealed brood phase of A.m. capensis may severely affect the ability of the mite to produce viable offspring. 2.) Africanised bees, a hybrid of African bee’s A.m. scutellata (Pretoria region) and European bees, are naturally tolerant to Varroa in South and Central America. Therefore, it was hoped that the African bees would show a similar natural tolerance towards the mite. Initially there were reports of honeybee colonies in South Africa that were apparently healthy despite harbouring tens of thousands of mites (M. ALLSOPP, pers. com.). Therefore, we compared the reproductive ability of mites invading sealed brood cells of A.m. scutellata with previous studies carried out on both Africanised and European bees. We showed that Varroa was able to reproduce at similar levels to those found in European bees which explained the huge mite populations previously reported. We also reviewed the developmental time of the A.m. capensis bee. We found that although they do process one of the shortest sealed brood developmental times found among A. mellifera races it is sufficient for Varroa populations to increase within these colonies. This finding was confirmed by some direct observations of the number of mature females emerging from cells occupied by A.m. capensis workers. It is proposed that the initial ability of the colonies to survive with large mite populations is due to the natural rarity of the overt form of key bee viruses such as deformed wing virus which is transmitted by the mite and leads to the collapse of the colony. Thus, it is predicted that once the viruses become established within the Varroa infested colonies, the wide spread bee losses that have occurred in many countries will occur in South Africa.