Responses to \u3ci\u3eVarroa destructor\u3c/i\u3e and \u3ci\u3eNosema ceranae\u3c/i\u3e by several commercial strains of Australian and North American honeybees (Hymenoptera: Apidae)

The potential impact of varroa (Varroa destructor, Anderson & Trueman) on Australian beekeeping and agriculture depends in part on the levels of resistance to this parasite expressed by Australian commercial honeybees (Apis mellifera). The responses of seven lines of Australian honeybees to V. destructor were compared with the responses of a stock of Italian honeybees from the United States known for its susceptibility to V. destructor and two stocks known for their resistance to V. destructor, Russian honeybees (RHB) and a stock expressing the varroa sensitive hygiene trait (VSH). The experiment began in May with uniform colonies having uniform infestation of V. destructor. V. destructor infestations measured as the percentage of adult bees infested in the Australian lines and the Italian stock rose from less than 10% in August to over 25% in October. From August to November, 44% of both the Australian and Italian colonies died while strongly exhibiting symptoms of parasitic mite syndrome. In contrast, RHB and VSH colonies displayed comparative resistance to V. destructor. Their infestation rates rose from about 5% in August to 10% (RHB) and 14% (VSH) in October. Likely, some of this increase resulted from invasion pressure by mites from the dying Australian and Italian colonies. During the August to November period, 4.4% of the RHB and 14.3% of the VSH colonies died. In comparisons of the seven Australian lines, only non-significant and trivial differences were found for infestation and mortality rates. All Australian lines were highly susceptible to V. destructor. Additionally, evaluations of rates of Nosema ceranae infections were made throughout the course of the experiment. Although high levels of infection were found across all stocks and lines, no stock or line exhibited an adverse effect from N. ceranae infection

Behavioral responses underpinning resistance and susceptibility of honeybees to Tropilaelaps mercedesae

Behavioral responses of Apis cerana, Apis dorsata, and Apis mellifera to the ectoparasitic mite, Tropilaelaps mercedesae, were compared using two laboratory bioassays: cohorts of 50 caged worker bees and individual-caged worker bees, all of unknown ages. For the group bioassays, ten T. mercedesae were placed on the bodies of bees in each cohort. After 6 h, nearly 2/3 of the mites placed on A. cerana had fallen from the bees onto sticky traps that were placed under the cages, compared to only about 1/3 for A. dorsata and A. mellifera. The majority of fallen mites fell within 24 h from A. cerana (93.3 ± 2.3%), 36 h from A. dorsata (92.2 ± 1.9%), and 48 h from A. mellifera (91.3 ± 1.4%). Higher proportions of injured mites were observed among the mites that fell from A. cerana (38.3 ± 12.9%) and A. dorsata (33.9 ± 17.4%) than among those that fell from A. mellifera (19.5 ± 7.2%). The rapid fall of mites from the bodies of A. cerana may be due to a combination of auto-grooming and rapid body shaking of the bees. In individual bee assays, where individual bees were challenged with one female T. mercedesae, A. cerana and A. dorsata exhibited faster behavioral responses to the presence of mites than did A. mellifera (39.4 ± 13.2, 44.9 ± 19.2, and 188.4 ± 63.9 s, respectively). Phoretic T. mercedesae were mostly observed attaching to the propodeum/petiole region of all three bee species, although some mites also occupied the wing base area of A. dorsata and A. mellifera.Keywords: Apis mellifera, Apis cerana, grooming behavior, Tropilaelaps mercedesae, Apis dorsataKeywords: Apis mellifera, Apis cerana, grooming behavior, Tropilaelaps mercedesae, Apis dorsat

Prevalence and reproduction of Tropilaelaps mercedesae and Varroa destructor in concurrently infested Apis mellifera colonies

The prevalence of Tropilaelaps mercedesae and Varroa destructor in concurrently infested A. mellifera colonies in Thailand was monitored. We also assessed the fecundity of T. mercedesae and V. destructor in naturally infested brood and in brood cells deliberately infested with both mite genera. Results showed that the natural co-infestation of an individual brood cell by both mite genera was rare (<0.1 %). Overall, T. mercedesae was the more dominant brood parasite of A. mellifera than V. destructor. In naturally infested brood, the proportion of nonreproductive Tropilaelaps (29.8 ± 3.9 %) was lower than that of Varroa (49.6 ± 5.9 %). Both mites produced similar numbers of progeny (T. mercedesae = 1.48 ± 0.05; V. destructor = 1.69 ± 0.14). The two mite genera also reproduced normally when they were deliberately introduced into the same brood cells. In two separate assessments, the average worker brood infestations of T. mercedesae (19.9 %) were significantly higher than that of V. destructor (0.7 %). Our results on the higher prevalence and reproductive ability of T. mercedesae in concurrently infested colonies reaffirm Tropilaelaps’ competitive advantage over V. destructor and their reported negative impact to A. mellifera colonies.Keywords: concurrent infestation, Tropilaelapsmercedesae, Varroa destructor, Apis mellifera, seasonal abundanc

Identification and comparison of Varroa species infesting honey bees

Varroa jacobsoni Oudemans, V. underwoodi Delfinado-Baker and Aggarwal and V. rindereri de Guzman and Delfinado-Baker are obligatory parasites of honey bees. The key morphological characters, host range and geographic distribution of these three species are reviewed. The occurrence of different genotypes of V. jacobsoni, their geographic distribution and virulence on honey bee hosts are discussed. © Inra/DIB/AGIB/Elsevier, Pari

Comparative Flight Activities and Pathogen Load of Two Stocks of Honey Bees Reared in Gamma-Irradiated Combs

Gamma irradiation is known to inactivate various pathogens that negatively affect honey bee health. Bee pathogens, such as Deformed wing virus (DWV) and Nosema spp., have a deleterious impact on foraging activities and bee survival, and have been detected in combs. In this study, we assessed the effects of gamma irradiation on the flight activities, pathogen load, and survival of two honey bee stocks that were reared in irradiated and non-irradiated combs. Overall, bee genotype influenced the average number of daily flights, the total number of foraging flights, and total flight duration, in which the Russian honey bees outperformed the Italian honey bees. Exposing combs to gamma irradiation only affected the age at first flight, with worker bees that were reared in non-irradiated combs foraging prematurely compared to those reared in irradiated combs. Precocious foraging may be associated with the higher levels of DWV in bees reared in non-irradiated combs and also with the lower amount of pollen stores in colonies that used non-irradiated combs. These data suggest that gamma irradiation of combs can help minimize the negative impact of DWV in honey bees. Since colonies with irradiated combs stored more pollen than those with non-irradiated combs, crop pollination efficiency may be further improved when mite-resistant stocks are used, since they performed more flights and had longer flight durations

The effects of diet, mating duration, female to male ratios, and temperature on ovary activation, mating success, and fecundity of Aethina tumida

International audienceThe effects of natural diet (brood, pollen, honey, and their various combinations), mating duration (1 day versus 2 days), female (F) to male (M) ratio (1F/1M, 2F/1M, and 1F/2M), and temperature (34 versus 27–29 °C) on ovary activation, mating success, and fecundity of small hive beetles (SHBs) were studied. Our results indicated that regardless of mating duration, (1) a diet of brood, pollen, and honey presented together supported the highest fecundity; (2) intake of protein-rich diets encouraged ovary activation and egg-laying; and (3) diet of honey alone did not encourage ovary activation, mating success, and egg-laying at room temperature. Regardless of the number of males available for mating, egg-laying varied through time. Overall, females that were presented with two males for a 5-day mating period had higher fecundity than females provided with one male or three male partners. High temperature accelerated ovary activation and egg-laying regardless of female to male ratio during a 15-h mating period. Knowledge of these factors that influence fecundity helps elucidate why SHBs are very successful pests of honey bees

Occurrence of two genotypes of Varroa jacobsoni Oud. in North America

Both the Russian and Japanese genotypes of Varroa jacobsoni were present in the United States and Canada. Only the Russian genotype was found in Mexico. Our results suggest that North America, and especially the United States has had more than one introduction of Varroa jacobsoni. Differences in virulence among strains of V. jacobsoni may be the basis for reports of regional variation in honey bee resistance to Varroa. Thus, further studies on the interaction between Varroa and honey bee genotypes are needed to fully resolve the issue. © Inra/DIB/AGIB/Elsevier, Pari

Breeding for resistance to

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