Amanda M. Frake

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.

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.

Associations of Parameters Related to the Fall of Varroa destructor (Mesostigmata: Varroidae) in Russian and Italian Honey Bee (Hymenoptera: Apidae) Colonies

ABSTRACT Varroa destructor (Anderson and Truman) trapped on bottom boards were assessed as indirect measurements of colony mite populations and mite fall in colonies of Russian and Italian honey bees using 29 candidate measurements. Measurements included damaged and nondamaged younger mites, damaged and nondamaged older mites, fresh mites and all mites, each as a proportion of total mites in the colonies and as a proportion of all trapped mites or all trapped fresh mites. Regression analyses were used to determine the relationships of these candidate measurements to the number of mites in the colonies. The largest positive regressions were found for trapped younger mites (Y) and trapped fresh mites (F). Measurments of Y and F across time could be used to estimate mite population growth for the purposes of selective breeding. The largest negative regressions with colony mites were observed for: trapped older mites/trapped mites (O/T), trapped older mites/trapped younger mites (O/Y), and trapped injured older mites/injured mites (IO/I). O/T and O/Y are significantly higher for Russian honey bee colonies suggesting that they are related to at least some of the mechanisms used by Russian honeybee to resist Varroa population growth. O/T and O/Y have strong negative relationships with colony mites for both Russian honey bee and Italian colonies suggesting that both strains possibly could be selected for reduced colony mites using O/T or O/Y.

Detection and removal of brood infested with eggs and larvae of small hive beetles (Aethina tumida Murray) by Russian honey bees

Summary The response of Russian honey bees to brood infested with small hive beetle (SHB) eggs and larvae was compared to that of a commercial stock (predominantly of A. m. ligustica). Test brood was grouped as follows: a) NoP = no perforation either of capping or cell wall; b) PWall = perforation of cell wall only; c) PCap = perforation of capping only; and d) PBoth = capping and cell wall perforations. All perforations were made by SHB. Our results showed that brood cells with perforations of the cell wall (PWall and PBoth) had the highest infestation (76.53 ± 2.10%) and number of eggs (58.46 ± 2.85 eggs). Because PCap showed low levels of infestation (29.17 ± 3.31% and 15.60 ± 1.31 eggs per infested cell), we calculated brood removal based on data from PWall and PBoth groups. Within 6 h, both stocks removed the contents of 39.24 ± 4.94% of PWall cells. A higher removal rate of 50.51 ± 5.80% was observed in PBoth cells. These two groups of brood had the highest numbers of eggs per infested cell (50–70 eggs). Eggs hatched after the 6 h observation and subsequent hygienic removal was of brood infested with larvae. At 20 h, additional 56.41 ± 4.62% (PWall) and 42.04 ± 4.91% (PBoth) removal rates were observed. Overall, the cumulative removal rates for both stocks were similar with means of 85.11 ± 2.98% and 84.32 ± 4.29% for the commercial and Russian honey bees, respectively. In conclusion, we observed that both honey bee stocks were able to detect eggs inside the sealed brood cells and remove them with the infested brood.

Phenotypic and Genetic Analyses of the Varroa Sensitive Hygienic Trait in Russian Honey Bee (Hymenoptera: Apidae) Colonies

Varroa destructor continues to threaten colonies of European honey bees. General hygiene, and more specific Varroa Sensitive Hygiene (VSH), provide resistance towards the Varroa mite in a number of stocks. In this study, 32 Russian (RHB) and 14 Italian honey bee colonies were assessed for the VSH trait using two different assays. Firstly, colonies were assessed using the standard VSH behavioural assay of the change in infestation of a highly infested donor comb after a one-week exposure. Secondly, the same colonies were assessed using an “actual brood removal assay” that measured the removal of brood in a section created within the donor combs as a potential alternative measure of hygiene towards Varroa-infested brood. All colonies were then analysed for the recently discovered VSH quantitative trait locus (QTL) to determine whether the genetic mechanisms were similar across different stocks. Based on the two assays, RHB colonies were consistently more hygienic toward Varroa-infested brood than Italian honey bee colonies. The actual number of brood cells removed in the defined section was negatively correlated with the Varroa infestations of the colonies (r2 = 0.25). Only two (percentages of brood removed and reproductive foundress Varroa) out of nine phenotypic parameters showed significant associations with genotype distributions. However, the allele associated with each parameter was the opposite of that determined by VSH mapping. In this study, RHB colonies showed high levels of hygienic behaviour towards Varroa -infested brood. The genetic mechanisms are similar to those of the VSH stock, though the opposite allele associates in RHB, indicating a stable recombination event before the selection of the VSH stock. The measurement of brood removal is a simple, reliable alternative method of measuring hygienic behaviour towards Varroa mites, at least in RHB stock.

A laboratory technique to study the effects of Varroa destructor and viruses on developing worker honey bees

Varroa destructor, laboratory-rearing, gel caps Journal of Apicultural Research 52(5): 262-264 (2013)

Effect of Height and Color on the Efficiency of Pole Traps for Aethina tumida (Coleoptera: Nitidulidae)

ABSTRACT Olfactory cues released by adult bees, brood, pollen, and honey from a honey bee, Apis mellifera L., colony are the primary stimuli that guide the beetle Aethina tumida Murray (Coleoptera: Nitidulidae) to host colonies. To investigate the response of adult A. tumida to visual stimuli, we tested the influence of color and height on trap efficiency. Two pole trap colors (black and white) were evaluated at three heights (46 cm, 1 m, and 3 m) from October 2008 to December 2009. A. tumida were trapped in the greatest numbers between 17 April and 15 May 2009. The lowest numbers were captured during the winter and fall. The trapping results showed that both color and trap height significantly influenced capture. The average catch in the white traps (mean ± SE, 2.47 ± 0.30) was significantly higher than that of the black traps (1.53 ± 0.29) probably because white is more reflective than black. Among the heights evaluated, there were more beetles caught when traps were positioned at 46 cm (the same height as the entrance of the hives) with 3.07 ± 0.51 beetles compared with beetles captured at 1 m (1.88 ± 0.30) or 3 m (1.06 ± 0.18) high. Male and female beetles exhibited similar responses to trap color and height. The relationship between the numbers of beetles in colonies and capture rates in traps was very poor and did not provide a basis to evaluate trap efficiency. In addition, because capture rates seemed generally low in relationship to the number of beetles in the apiary, substantial improvements to the trap may be necessary.

Seasonal population dynamics of small hive beetles, Aethina tumida Murray, in the south-eastern USA

Summary The population of small hive beetles, Aethina tumida (SHB), was monitored from 2005 to 2008 in colonies of Italian and Russian honey bees located near St. Gabriel, Louisiana, USA. SHB populations differed between honey bee strains (only in one site out of two), with Italian colonies supporting more beetles (7.45 ± 0.98 SHB per colony) than the Russian colonies (4.48 ± 0.51 SHB per colony). No difference between the two strains was observed at site 1 where the SHB population was generally low (Italian = 2.73 ± 0.36 SHB; Russian = 2.69 ± 0.57 SHB per colony). Our results also revealed that SHB populations varied throughout the year, with peak infestations observed in the autumn (September and November). SHB abundance was significantly correlated with the proportion of hot days, but not with the proportions of cool, dry, or humid days, or the percentage of days with rainfall. Our results suggest that in-hive autumn trapping of SHB in the south eastern USA may reduce springtime numbers of SHB.

Comparative Resistance of Russian and Italian Honey Bees (Hymenoptera: Apidae) to Small Hive Beetles (Coleoptera: Nitidulidae)

ABSTRACT To compare resistance to small hive beetles (Coleoptera: Nitidulidae) between Russian and commercial Italian honey bees (Hymenoptera: Apidae), the numbers of invading beetles, their population levels through time and small hive beetle reproduction inside the colonies were monitored. We found that the genotype of queens introduced into nucleus colonies had no immediate effect on small hive beetle invasion. However, the influence of honey bee stock on small hive beetle invasion was pronounced once test bees populated the hives. In colonies deliberately freed from small hive beetle during each observation period, the average number of invading beetles was higher in the Italian colonies (29 ± 5 beetles) than in the Russian honey bee colonies (16 ± 3 beetles). A similar trend was observed in colonies that were allowed to be freely colonized by beetles throughout the experimental period (Italian, 11.46 ± 1.35; Russian, 5.21 ± 0.66 beetles). A linear regression analysis showed no relationships between the number of beetles in the colonies and adult bee population (r 2 = 0.1034, P = 0.297), brood produced (r 2 = 0.1488, P = 0.132), or amount of pollen (r 2 = 0.1036, P = 0.295). There were more Italian colonies that supported small hive beetle reproduction than Russian colonies. Regardless of stock, the use of entrance reducers had a significant effect on the average number of small hive beetle (with reducer, 16 ± 3; without reducer, 27 ± 5 beetles). However, there was no effect on bee population (with reducer, 13.20 ± 0.71; without reducer, 14.60 ± 0.70 frames) or brood production (with reducer, 6.12 ± 0.30; without reducer, 6.44 ± 0.34 frames). Overall, Russian honey bees were more resistant to small hive beetle than Italian honey bees as indicated by fewer invading beetles, lower small hive beetle population through time, and lesser reproduction.

Brood removal influences fall of Varroa destructor in honey bee colonies

The hygienic removal of Apis mellifera brood infested with Varroa destructor disrupts the reproduction of the infesting mites, and exposes the foundress mites to potential removal from the colony by grooming. Using brood deliberately infested with marked mites, we investigated the association between the removal of mite-infested brood and the removal of exposed foundress mites in Italian (IHB) and Russian honey bee (RHB) colonies. Our results showed that RHB colonies removed more mite-infested brood in significantly less time (average = 87.9 ± 2.0% for 2.6 ± 0.1 days) than IHB colonies (average = 61.9 ± 7.3% for 3.2 ± 0.1 days or 19.3% per day). For the inoculated brood that was not removed, RHB colonies had lower proportions of brood cells containing: (a) live marked mites regardless of reproductive status (RHB = 4.4 ± 1.3%; IHB = 17.7 ± 5.9%); (b) dead marked mites (RHB = 1.1 ± 0.5%; IHB = 7.1 ± 2.2%); (c) lost introduced marked mites (RHB = 6.6 ± 1.6%; IHB = 13.3 ± 2.8%); and (d) reproductive marked mites (RHB = 8.3 ± 6.3%; IHB = 23.8 ± 6.9%) than IHB colonies did. These observations suggest that RHB colonies indiscriminately remove mite-infested brood regardless of mite status. Regarding trapped mites (i.e., those found below a modified queen excluder), the number of mite-infested brood cells removed positively correlated with the number of mites that were trapped in both honey bee stocks. The majority of the trapped mites fell during the first three days post mite inoculation, which coincided with the highest rates of brood removal. The highest proportions of trapped gravid foundress mites were also recorded during this time, when host bees were early in their development. The comparatively strong and rapid hygienic response of RHB to mite-infested brood and the associated removal of infesting foundresses are probably parts of a suite of factors responsible for suppressing V. destructor populations in RHB colonies.