Sunday, 10 January 2016

NOSEMA: Instructions for Sampling


1) Find suitable containers for each sample, either a plastic bag, plastic box (an empty, clean margarine tub is a good idea) or empty honey jar.

2) Write your name, hive reference and apiary location on the outside of each container.

3) Thirty (30) mature bees will be needed for the test. To achieve this it will be easiest to catch flying bees around the entrance.

4) Choose a day and time when the bees are flying actively.

5) Close the entrance for a while until returning bees are crowding the entrance.

6) Brush or scoop 30+ bees into the container – it can be done!

7) Seal the container, check the label and place in a freezer immediately.

8) Remove the bees from the freezer only on the day of the test to minimise decomposition.

9) Bees and details can be sent with a fellow member on the day.

10) Privacy and confidentiality will be respected and personal information will not be passed onto any other organisation.

All samples to be given to Divisional Testing Team.


Nosema Testing

DMBKA will be offering Nosema apis testing in March 2016!  Contact Secretary for more information;

Nosema species

Two Nosema species have been identified in honey bees in England and Wales, Nosema apis and more recently the Asian species Nosema ceranae. Both are highly specialised parasitic Microsporidian fungal pathogens. Nosema spp. invade the digestive cells lining the mid-gut of the bee, there they multiply rapidly and within a few days the cells are packed with spores, the resting stage of the parasite. When the host cell ruptures, it sheds the spores into the gut where they accumulate in masses, to be later excreted by the bees. If spores from the excreta are picked up and swallowed by another bee, they can germinate and once more become active, starting another round of infection and multiplication.

Symptoms of Nosema

There are no outward symptoms of the disease. Dysentery is often seen in association with N. apis infections; this may be seen as 'spotting' at the hive entrance or across the frames. The dysentery is not caused by the pathogen, but as a consequence of infection and can be exacerbated during periods of prolonged confinement during inclement weather, especially during the spring. This can lead to the bees being forced to defecate in the hive, therefore contaminating it further.

In Spain it has been reported that N. ceranae infections are characterised by a progressive reduction in the number of bees in a colony until the point of collapse. The beekeeper may also see a significant decline in colony productivity. In the final phase of decline, secondary diseases frequently appear, including chalk brood and American foul brood. Eventually the affected colonies contain insufficient bees to carry out basic colony tasks and they collapse. Mortality in front of the hives is not a frequent symptom of N. ceranae infection. Dysentery and visible adult bee mortality in front of the hives are reported to be absent in N. ceranae infections. Colonnies can fail to build up and even dwindle away. This can sometimes be rapid or take place over several months.

Nosema is readily spread through the use of contaminated combs. The spores can remain viable for up to a year, it is therefore important not to transfer contaminated combs between colonies and as always to practice good husbandry and apiary management, maintaining vigorous, healthy stocks, which are better able to withstand infestations.

Diagnosis and Treatment

The simplest method of diagnosis of infections is by microscopic examination. Both N. apis and N. ceranae can be identified in adult bee samples using a standard adult disease screen - under the light microscope the spores of N. apis and N. ceranae appear as white/green, rice shaped bodies. However, both species are virtually identical when viewed using conventional microscopy, but can be distinguished by an expert eye. However, more accurate discriminatory tests are available which detect differences between the two species using genetic methods. Researchers in the NBU, in conjunction with Fera staff in the Molecular Technology Unit, have developed methods based on real-time PCR; a sensitive method which can detect and quantify low levels of pathogen infection.

Treating with medicines

The marketing authorisation for Fumidil B expired on the 31st December 2011. Any existing stocks of the product can be used up until the end of the expiry date shown on the packaging. For up-to-date advice on the availability of medicines please visit the VMDwebsite. As with all medicines ensure that the label instructions are followed.

Good husbandry

Instead of using medicines for treatment of Nosemosis, beekeepers should to maintain their colonies in good health apply good husbandry practices; such as maintaining strong, well fed and disease tolerant colonies, headed by young and prolific queens. Bee keepers should also consider re-queening susceptible colonies with queens from more tolerant stocks of bees better able to cope with Nosema infection.

Further Information
Nosemosis of the Honey bee, OIE Terrestrial Manual 2008 (pdf)

Bee Craft article: Nosema ceranae, Jan 2008 (pdf)

how to take samples

National Bee Unit
Price List

Adult Bee Disease Diagnosis

The National Bee Unit offers honey bee disease screening services. Please note that there is no service provided for screening for foulbrood pathogens. Detection of foulbrood disease is part of the Statutory risk based inspections programme.

  1. Standard Adult Bee Disease Diagnosis - Cost = £40.00. A sample of 30 bees will be individually screened using standard microscopic techniques for the presence of Acarine, Nosema spp and Amoeba. Please send a cheque made payable to: Animal and Plant Health Agency.
  2. Screening for presence of Nosema spp - Cost = £10.00 A sample of 30 bees will be tested using standard microscopic techniques for the presence of Nosema spp (positive/negative result). Please send a cheque made payable to: Animal and Plant Health Agency.
Molecular pathogen screening (TaqMan® PCR)

Please see Fera Science Ltd website for the Detection & Surveillance Technologies available.

Contact Fera for further information on services provided and prices:

Telephone: +44 (0)1904 462 745

Spring treatment with oxalic acid in honeybee colonies as varroa control

Spring treatment with oxalic acid in honeybee colonies as varroa control
Camilla J. Brødsgaard, Sten Erik Jensen & Henrik Hansen
Danish Institute of Agricultural Sciences
Department of Crop Protection
Research Centre Flakkebjerg
DK-4200 Slagelse 

Carsten W. Hansen
Danish Beekeeper's Association
Møllevej 15
DK-4140 Borup 
spring_treatment_oxalic_acid_1.jpg (6925 octets)
Oxalis acetocella L. Wood Sorrel
(modified from Lindman 1974)

punaise_r.gif (643 octets)SUMMARY
In late March 1998, 30 honeybee colonies (Apis mellifera) in four apiaries were treated for the parasitic mite (Varroa jacobsoni) with either spraying or trickling of oxalic acid. Four colonies were not treated and served as controls. Prior to the treatment, eight days after the treatment, and at the first honey harvest in June one food sample was taken in each colony. Of these samples five from sprayed, five from trickled, and the four from control colonies were chosen and the oxalic acid residue level was determined by means of liquid chromatography. The results showed that the maximum residue level was found eight days after treatment in the sprayed group (average max. = 0.0062%) but also that there was no significant difference in oxalic acid concentration between the groups at any of the sampling dates.

In another apiary, the glutathione S-transferase (GST) activity was measured in individual pupae and adult bees from trickled and control colonies. The result showed that 15 days after treatment the GST activity in pupae and adult bees from the trickled colonies was not different from the GST activity found in non-treated colonies indicating that trickling treatment of colonies with oxalic acid does not seem to have an effect on the level of GST activity in pupae or newly emerged adult bees. 

The varroa mortality was recorded after the spring treatments with oxalic acid trickling and spraying and again in the autumn after an oxalic acid trickling treatments. Furthermore, the bee colony strength and brood amount were recorded prior to the spring treatment and again a year after the treatments. A significant difference in varroa mortality was seen after the spring treatment between the treated colonies and the controls. In the trickling group the total mite drop-down per colony was in average 61.53, in the sprayed group it was 145.47 and in the control group 1.50. After the autumn treatment, no significant difference was found between the three groups and the mite drop-down ranged between 936 and 1,400 mites. In 1998, the mean bee colony strength was approximately 5.5 comb gates before the treatment. At the same time the mean brood amount ranged from 1.77 to 3.25 dm2. During the 1998 season, no difference in colony development was observed among the three trial groups. One year after the treatments the mean colony strength ranged from 4.93 to 6.25 comb gates. The brood amount ranged from 0.89 to 1.53 dm2. There was no significant difference between the treated groups and the control group at any time. 

punaise_r.gif (643 octets)INTRODUCTION
Several studies have shown that formic (Fries 1991) and lactic acid (Koeniger et al. 1983, Klepsch et al. 1984, Kraus 1991, Brødsgaard et al. 1997) are effective in controlling infestation with the parasitic mite Varroa jacobsoni Oudemans on honeybees (Apis mellifera, L.). However, in laboratory tests oxalic acid was even more poisonous than the two former organic acids to varroa mites (Fuchs, pers. comm.). In field tests Radezki (1994) found very high mite mortality (97,3%) when spraying 3% oxalic acid on adult mite infested bees. 

Though oxalic acid is found naturally in very low concentrations in e.g. spinach and rhubarb (Fassett 1973) it may be harmful to humans even in low concentrations. Oral ingestion of oxalic acid may be deadly, by dermal contact it may cause damage to the skin and tissue and by inhalation it may cause damage to the mucous membranes. Therefore, it is necessary that precautions are taken while spraying oxalic acid (appropriate use of mask, gloves, and glasses) (Radezki 1994). 

To avoid oxalic acid in aerosol form, the application of oxalic acid has been further developed in Italy by Nanetti and Stradi (1997). They found that one application of oxalic acid by trickling an oxalic acid sugar solution onto the frames in the colonies provided efficacies ranging from 89,6% to 96,8% depending upon the oxalic acid concentration. 

However, besides being harmful to the varroa mites, physiological effects on the bees in the colonies treated with oxalic acid by the trickling method has been suggested (W. Ritter, pers. comm., A. Imdorf, pers. comm.). The hypothesis is that the bees ingest some of the oxalic acid-sugar solution during the treatment leading to damage on tissues of the digestive system. If tissues with glutathione S-transferase (GST) activity are damaged, a possible effect could be a lowering of the level of GST activity. It has been shown that several different tissues, including gut tissues have GST activity in honeybees and other insects (e.g. Clark 1989, El-Ghareeb & Omar 1994). The GST enzymes are an important group of enzymes for eliminating harmful substances that the bees come into contact with (Smirle & Winston 1988, Yu et al. 1984). A lowering of the level of GST activity could make the bees more vulnerable to toxic substances in the environment. Therefore a treatment of bees that results in a lowering of the level of GST activity may influence their overall fitness. 
This study includes preliminary results on the use of GST activity as a biological marker for possible physiological effects on bees from oxalic acid treated colonies. 

Furthermore, residue levels in honey have only been studied after oxalic acid treatment in autumn and early winter (Radezki 1994, Nanetti & Stradi 1997) and in Denmark the need for an efficient spring treatment is profound. Therefore, a further aim of this study has been to examine the residue levels of oxalic acid after treatment of bee colonies in the spring time with either spraying or trickling of oxalic acid. To get an impression of differences in the treatments the varroa mortality was monitored shortly after the spring treatment and again in the autumn after a second single treatment with oxalic acid trickling. 

punaise_r.gif (643 octets)MATERIALS & METHODS
Oxalic acid treatment
In spring 1998 (23 March), totally 35 honeybee colonies in five apiaries in Denmark were treated with oxalic acid. The colonies were naturally infested with varroa mites. In both the first and the second apiary four bee colonies were sprayed, four were trickled and one untreated colony served as control. In the third apiary three bee colonies were sprayed, four were trickled, and one untreated colony served as control. In the fourth apiary four bee colonies were sprayed, three were trickled, and one untreated colony served as control. The treated colonies were selected randomly within the apiaries. The colonies in the last apiary were used for assaying GST activity in the bees (see below). In this apiary five randomly selected bee colonies were trickled and five untreated colony served as controls. 

For spray treatment an oxalic acid solution was made of 30 g oxalic acid crystals (oxalic acid dihydrate) dissolved in 1 l demineralised water (Radetzki 1994). 3-4 ml per comb side were sprayed (Imdorf et al. 1996) with a hand operated atomiser (Ginge®, 0.5 l, no. 20-05-00, adjusted to the finest atomisation). 

Trickling with oxalic acid sugar solution using 1 part (weight) oxalic acid dihydrate, 10 part demineralised water, 10 parts sucrose (Nanetti & Stradi 1997). 3 ml were trickled with a syringe per fully occupied comb gate. E.g. totally, 30 ml were used for a weak bee colony, 40 ml for a medium strong bee colony and 50 ml for a strong colony (Imdorf et al. 1998). 

Climatic measurements
The outdoor temperature was above 5 deg. C and the oxalic acid solutions were approximately 10 deg. C before the treatment. Outdoor temperature and relative air humidity (RH) were recorded in the apiaries at the time of the treatment by Tiny Talk® data loggers at 17 mins interval and continued for three weeks. 

Varroa mortality
In the colonies in the apiaries 1-4 the varroa mortality was recorded in specially designed wooden inserts covering the entire bottom board every second day for four weeks after treatments. The inserts were emptied each sampling date. Furthermore, the varroa mortality was calculated in all bee colonies after one trickling treatment with oxalic acid in the autumn 1998. At the time of the autumn treatment no brood was present in the colonies. The results were analysed statistically by means of Kruskal-Wallis Multiple Comparisons (K-W) (Siegel and Castellan, 1988). 

Bee colony strength
In the apiaries 1-4 the amount of brood was estimated in dm2 by visually dividing the capped brood into squares. The bee colony strength was estimated as the number of comb gates occupied by the bees when looking into the colony without removing the combs. The estimations were carried out before the treatment and again one year after the treatment. The results were analysed statistically by means of Kruskal-Wallis Multiple Comparisons (K-W) (Siegel and Castellan, 1988). 

Oxalic acid residues
In the apiaries 1-4 one food sample was taken in each of the colonies before treatment. Eight days after the treatment one sample of unsealed food or honey were taken in each of the colonies. Furthermore, one sample of the first honey harvest (early June) were taken in each of the colonies. The samples were stored in darkness at 20 deg. C until processing. In the apiaries 1-4, five sprayed, five trickled, and four control colonies were randomly chosen and analysed for oxalic acid residues by liquid chromatography at Instituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Italy. The results were analysed statistically by means of Kruskal-Wallis Multiple Comparisons (K-W) (Siegel and Castellan, 1988). 

Glutathione S-transferase (GST) activity
In the fifth apiary, pupae and newly emerged adult worker honeybees were collected from the colonies. Pupae were collected immediately before oxalic acid trickling treatment (as mentioned above) in five colonies and again 15 days after the treatment. Newly emerged adult bees were collected 15 days after the oxalic acid treatment. As control, individuals were collected simultaneously from five non-treated colonies at the same locality. After collection the individual pupae and adults were stored at -80 deg. C until assayed. 

Reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB) were purchased from Merck (Darmstadt, Germany), 1-phenyl-2-thiourea (PTU) was purchased from Aldrich (Milwaukee, WI) and ethylenediaminetetraacetic acid (EDTA) was purchased from Sigma Chemical Co. (St. Louis, MO). The Bradford dye reagent and bovine serum albumin (fraction V) were purchased from Pierce (Rockford, IL). All other chemicals were of analytical quality and purchased from commercial suppliers. 

Homogenisation of pupae or adult bees for in vitro analysis
Whole pupae or whole adult bees were homogenised individually in 0.1 M sodium phosphate buffer (pH 6.5) containing 10 mM GSH, 1 mM PTU and 1 mM EDTA. The individuals were homogenised manually in microtubes held on ice. The homogenate was centrifuged at 10,000 g for 20 min at 4 deg. C and the supernatant was used in the assays. 

GST and protein assays
All measurements in the GST and protein assays were made at an ambient temperature (20-25 deg. C) and absorbance was recorded using a Multiskan MCC/340 microplate reader (Labsystems, Finland). 

GST activity was measured with CDNB as substrate as described by Habig et al. (1974) and modified for a microplate. Assays were done on homogenate diluted with homogenisation buffer to an appropriate concentration. Diluted homogenate (20 l) was added per well in a microplate and 180 l of GSH (10 mM final concentration) and CDNB (1.0 mM final concentration) in 0.1 M sodium phosphate buffer (pH 6.5) was added to each well. The microplate was left 5 min to equilibrate and then absorbance at 340 nm was recorded continuously. Reaction rates were calculated by linear regression analysis on the linear portion of the curve after plotting absorbance against time. Duplicate determinations were made on each individual. 

Protein content in homogenates was determined by the method of Bradford (1976), as modified in the Pierce standard assay for microplates, with bovine serum albumin as a standard. 

The GST activity was measured in individuals from non-treated colonies and in individuals from colonies trickled with oxalic acid. Eight individuals were assayed from each colony. GST activity was assayed 15 days after oxalic acid trickling treatment of the colonies. Concerning the pupae, GST activity was also measured in individuals collected immediately before treatment.

punaise_r.gif (643 octets)RESULTS
Climatic measurements
On the day of the oxalic acid treatments the outdoor day temperature was 17.0 C. In the following four weeks the temperature ranged between 0.6 C at night and 26.3 C in daytime with an average of 7.0 C. On the day of the treatments the relative humidity (RH) was 28.6 %. In the following 4 weeks the RH ranged between 21.9% and 100.0% with an average of 86.2%. 

Varroa mortality
After the spring treatment, the mean varroa mortality increased in the treated groups reaching a maximum daily mite drop-down (±S.E.M.) of 24.0±5.52 per colony in the trickled group and of 64.93±30.51 in the sprayed group 4 days after treatment. At that time the control group had a mean drop-down of 0.25±0.25 varroa mites. Hereafter, the daily drop-down in the treated groups decreased continuously to 0.47±0.24 in the trickled group and 0.27±0.21 in the sprayed nearly reaching the control level of 0.00, four weeks after the treatment (FIGURE 1). The total mean varroa drop-down (±S.E.M.) in the trickled group in the spring sampling period was 61.53±15.42 mites, in the sprayed group it was 145.47±66.68 and in the control group 1.50 ±0.29. The result of the control differed significantly from the treated colonies (K-W, p<0.05). 

After the autumn trickling treatment, the group treated with trickling in spring had a mean varroa drop-down (±S.E.M.) of 1,250.00±333.33. In the sprayed group the mean drop-down (±S.E.M.) was 935.80±391.53. The group serving as control in spring had a mean varroa drop-down (±S.E.M.) of 1,400.00±377.49 (FIGURE 2). The differences in varroa mortality were not significant (K-W, p>0.05). 

Bee colony strength
The mean bee colonies strength (±S.E.M.) was 5.5±0.96 comb gates in the control group, 5.4±0.30 comb gates in the sprayed and 5.53±0.45 comb gates in the trickled group before the treatment. There was no significant difference between the results (K-W, p>0.05). The mean brood amount (±S.E.M.) in the above mentioned groups was 3.25±0.75 dm2, 2.07±0.30 dm2 and 1.77±0.51 dm2, respectively. The results did not differ significantly (K-W, p>0.05). During the 1998 season, the oxalic acid treated colonies seemed to develop as well as the control colonies. One year after the treatment the mean colony strength (±S.E.M.) was 6.25±0.48 comb gates in the control group, 4.93±0.33 in the sprayed and 5.00±0.33 in the group trickled in spring 1998. The brood amount in the respective groups at the same time was 1.50±0.61 dm2, 1.53±0.67 dm2 and 0.89±0.24 dm2. There was no significant difference between the treated groups and the control (K-W, p>0.05). 

Oxalic acid residues
Just before the spring treatments the mean natural concentration of oxalic acid (±S.E.M.) was measured to be between 19.56±0.83 ppm and 35.85±5.96 ppm in the three experimental groups (FIGURE 3). Eight days after the treatment the oxalic acid concentration was increased in the treated groups compared to before treatment but only the increase in the sprayed group to 62.84±15.88 was significant (K-W, p<0.05). At the first honey harvest in June the mean natural concentration of oxalic acid (±S.E.M.) was measured to be 37.78±5.55 ppm in the sprayed group, 41.56±8.54 in the trickled group and 57.70±7.95 ppm in the control group. There was no significant difference in oxalic acid concentration between the groups at any of the sampling dates (K-W, p>0.05). 

Glutathione S-transferase activity
The results for the GST activity in pupae are summarised in TABLE 1 and the results for the newly emerged adults are summarised in TABLE 2.
spring_treatment_oxalic_acid_2.gif (8422 octets)
FIGURE 1. Varroa drop-down on wooden inserts after trickling or spraying treatment with oxalic acid. The treatment was carried out 23 March 1998.

spring_treatment_oxalic_acid_3.gif (8683 octets)
FIGURE 2. Varroa drop-down on wooden inserts after trickling treatment with oxalic acid. The colonies were treated in spring '98 with trickling, spraying or no treatment, respectively. The autumn treatment was carried out in September.

spring_treatment_oxalic_acid_4.gif (11798 octets)
FIGURE 3. Concentration of oxalic acid residues in honey after spring treatment of bee colonies with oxalic acid by trickling. Black arrow indicates treatment, white arrow indicates honey harvest.
The data from the GST assays on the pupae were analyzed by one way analysis of variance with multiple comparison (Tukey's test, Zar 1996). The only groups that were significantly different (P<0.05) were pupae from non-treated colonies collected before treatment (184.4±5.8 nmol min-1 mg protein-1) and pupae from colonies treated with oxalic acid (207.0±4.2 nmol min-1 mg protein-1). Thus, 15 days after treatment the GST activity in pupae from the treated colonies was not significantly different from the GST activity in pupae from the same colonies before treatment and not significantly different from the GST activity in pupae from non-treated colonies collected at the same time. 
The data from the GST assays on the newly emerged adult bees was analysed by test (Zar 1996) and the test showed that the two groups were not significantly different (P=0.14). Thus, 15 days after treatment the GST activity in the adults from the oxalic acid trickled colonies were not different from the GST activity found in adults from non-treated colonies.
TABLE 1. Glutathione S-transferase (GST) activity in honeybee pupae collected before treatment and 15 days after trickling treatment with oxalic acid (OS)
Collection of pupae for GST assaysPupaenGST activitya(nmol min1 mg protein1)
Collection before treatment
 Pupae from five non-treated colonies40184.4±5.8
 Pupae from five colonies to be trickled with OS after collection40194.1±5.5
Collection 15 days after treatment of the colonies
 Pupae from five non-treated colonies40191.5±4.8
 Pupae from five colonies trickled with OS40207.0±4.2
a Mean activity ± SEM.
TABLE 2. Glutathione S-transferase (GST) activity in newly emerged adult honeybees collected 15 days after trickling treatment with oxalic acid (OS).
Adult bees
GST activitya
(nmol min1 mg protein1
Adults from four non-treated colonies
Adults from four colonies treated with OS trickling
a Mean activity ± SEM.

punaise_r.gif (643 octets)DISCUSSION
At the time of the oxalic acid treatments the bee colonies' strength and brood amount were average for Danish conditions. Neither eight days after the March treatment, nor at the first honey harvest in June a significant difference could be detected in oxalic acid concentration in food or honey between the treated groups and the control group. Eight days after the treatment the maximum level of oxalic acid was found in the sprayed group with a mean concentration of 0.0062%. For comparison, the natural concentration of oxalic acid (oxalates) based on fresh weight in spinach is 0.3-1.2%, in rhubarb 0.2-1.3%, in tea 0.3-2.0% and in cocoa 0.5-0.9% (Fassett 1973). Since oxalic acid is not fat-soluble no residues will build up in the wax in the treated colonies (Imdorf et al. 1998). Thus, residues in honey and wax after spring treatment with oxalic acid seems not to be problematic. 
If a difference in GST activity from treated vs. non-treated colonies was found it could be an indication of a physiological effect on individuals in the treated colonies. In this study trickling treatment of colonies with oxalic acid does not seem to have a prolonged negative effect on the level of GST activity in pupae or newly emerged adults as no difference in GST activity in treated vs. non-treated colonies could be demonstrated. However, a lack of effect on the level of GST activity does not rule out that individuals in oxalic acid treated colonies were physiologically affected by the treatment. 

During the season 1998, the treated colonies seemed to develop normally compared to the control colonies. Other Danish trials using the same methods in springtime confirm this finding (Hansen 1999). Only one of the treated colonies in the present study did not survive the winter 98/99. In spring 1999, the colonies in the present study had strength ranging from 4.93 to 6.25 comb gates and a brood amount of 0.89 to 1.53 dm2 which corresponds with the average in bee colonies at that time the country. 
The results of this study do not give a direct measure of the efficacy of the two treatments. Oxalic acid spraying does not have an effect on varroa mites in the sealed brood (Radetzki 1994). Also trickling is only recommended in broodless colonies as experiments have suggested that the efficacy of one treatment in colonies with brood was too poor and several treatments weakened the colonies (Imdorf et al. 1998). Because of the brood present in our colonies, we assume that the efficacy of these spring treatment is lower than the approximately 98% found by Radezki (1994) and Imdorf et al. (1998) for spraying and trickling, respectively. In spring in Denmark, it is not possible to cut out the brood to increase the efficacy as it is done in the autumn by lactic acid treatment (Brødsgaard et al. 1997). Removing the brood in spring would most likely weaken the colonies. A proper efficacy test should of course be followed by a total count of mites in the colonies or a treatment with a pesticide with a well-documented effect. But since there are no pesticides registered for use in Denmark the honey, wax and equipment from the treated colonies would have to be destroyed and this was not possible in this preliminary study. Nevertheless, assuming that the varroa infestation was evenly distributed between the colonies there seems to be a tendency that the spraying treatment was more efficient than the trickling based on the observed varroa drop-down although the difference was not significant (FIGURE 1). The lack of difference in efficacy between trickling and spraying treatment corresponds with the findings of Imdorf et al. (1998) who found no differences when treating broodless colonies in autumn with the two methods. The varroa drop-down after the trickling treatment in the autumn showed that the varroa population in the colonies treated in spring seemed to have developed as well as in the control. That result could be explained by a poor efficacy of the spring treatment, reinvasion from the control colonies to the treated colonies combined with a very short persistence of oxalic acid or the very few control colonies. 

Neither the residues of oxalic acid in honey, the GST activity, nor the colony development after spring treatment with either trickling or spraying with oxalic acid seem to indicate any problems. However, before the use of oxalic acid as spring treatments is recommended in Denmark it is necessary to put more effort into efficacy tests with a large number of control colonies in field trials.

punaise_r.gif (643 octets)ACKNOWLEDGEMENTS
We thank beekeeper G. Borg for cooperation, L. Hasmark and A. Marthin for their technical help and Instituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Italy for analysing honey samples for oxalic acid residues.

punaise_r.gif (643 octets)REFERENCES
Bradford, M.M. (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 72: 248-254. 

Brødsgaard, C. J., Hansen, H. & Hansen, C. W. (1997) Effect of lactic acid as the only control method of varroa mite populations during four successive years in honey bee colonies with a brood free period. Apiacta XXXII: 81-88. 
Clark, A.G. (1989) The comparative enzymology of the glutathione S-transferases from non-vertebrate organisms. Comp. Biochem. Physiol. B 92: 419-446. 
El-Ghareeb, A.M. & Omar, M.O.M.. (1994) Glutathione transferase in silkworm larvae and honeybee workers. Assiut J. Agric. Sci. 25: 181-189. 
Fassett, D. W. (1973) Toxicants occurring naturally in foods, chap. 16: Oxalates, p.346-362. National Academy of Sciences, Washington, D.C., USA.
Fries, I. (1991) Myrsyrabehandling och biotekniska metoder för bekämpning av varroakvalster (Varroa jacobsoni) i bisamhällen. Report 204. Uppsala: Swedish University of Agricultural Sciences : 1- 42. 
Habig, W.H., M.J. Pabst &. Jakoby, W.B (1974) Glutathione S-transferases: The first enzymatic step in mercapturic acid formation. J. Biol. Chem. 249: 7130-7139. 
Hansen, C. W. (1999) Forsøgsrapport 1998. Tidsskrift for Biavl 3: 16 pp. 
Imdorf, A., Charrière, J.-D., Maquelin, C., Kilchenmann, V.& Bachofen, B. (1996) Alternative varroa control. Amer. Bee J. 3: 189-193. 
Imdorf, A., Charrière, J.-D., Kilchenmann, V., Bachofen, B., Bogdanov, S. & Fluri, P. (1998) Wie können dir resistenten Varroa-Milben unter der Schadenschwelle gehalten werden? Forschungsanstalt für Milchwirtschaft (FAM) Sektion Bienen, Liebefeld, Schweiz. Mitteilung der Sektion Bienen nr. 27: 27 pp. 
Klepsch, A., Maul, V., Koeniger, N. & Wachendörfer, G. (1984) Einsatz von Milchsäure im Sprühverfahren zur Bekämpfung der Varroatose. Die Biene 120: 199-202 & 261-262. 
Koeniger, N., Klepsch, A.& Maul, V. (1983) Zwischenbericht über den Einsatz von Milchsäure zur Bekämpfung der Varroatose. Allg. Dtsch. Imkerztg. 17: 209-211. 
Kraus, B. (1991) Milchsäure als Varroatose-Therapeutikum. Die Biene 8: 427-430. 
Lindman, C. A. M. (1974) Nordens flora, bind 6. Gyldendal, Danmark. 
Nanetti, A. & Stradi, G. (1997) Oxalsäure-Zuckerlösung zur Varroabekämpfung. Allg. Dtsch. Imkerztg. 11: 9-11. 
Radetzki, T. (1994) Oxalsäure, eine weitere organische Säure zur Varroabehandlung. Allg. Dtsch. Imkerztg. 12: 11-15. 
Siegel S., Castellan N.J.Jr. (1988) Nonparametric Statistics, McGraw-Hill Book Co, Singapore. 
Smirle, M.J. & Winston, M.L. (1988) Detoxifying enzyme activity in worker honey bees: an adaptation for foraging in contaminated ecosystems. Can. J. Zool. 66: 1938-1942. 
Yu, S.J., Robinson, F.A. & Nation, J.L. (1984) Detoxication capacity in the honey bee, Apis mellifera L. Pestic. Biochem. Physiol. 22: 360-368. 
Zar, J.H. (1996) Biostatistical Analysis. Prentice-Hall, New Jersey.

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Sunday, 3 January 2016

Bee vision

Bee Vision

“Bees vision is different from ours… Bees can see ultraviolet, which we cannot, but their eyes cannot receive the long wavelengths on the red end of the color spectrum. A flower that we call white looks blue to a bee. Brilliant ultraviolet nectar guides – straight lines pointing to the interior of a light-blue flower – shimmered deep blue in one of Dr. Erickson’s slides of a bee’s vision… Since bees and their kin do not perceive red, plants with red flowers are bird-pollinated.” From Sue Hubbell’s A Book of Bees.
This, to me at least, is the coolest passage in the book. How we, and other animals, see things is such an interesting subject. Especially on the comparative level, because some of the differences between how we interact with the objects around us are absolutely striking. Some animals can even make a “picture” of what they “see” without even using their eyes! Like fish and electric fields, or animals that use echolocation. Nothing makes these differences more apparent than plants and how they interact with their pollinators by sight and smell.
Back when I tool Biology 203, there was a dichotomous key in the lab manual that had a wonderful list of color and odor (as perceived by humans), and what pollinators were attracted to it. For simplicity, I have made a table of what the key says (since keys can be difficult to read, and it’s a relatively simple table.)
ColorWhite, green, or purpleWhite or greenBright white, yellow, or blueOrange, red, or whiteRed or purpleBrown or purpleRed, purple, pink, or whiteGreen or brown, no petals
SmellStrong smellNone, or a strong fruity smellFresh, light smellNoneFresh, light smellStinkyStrong, sweet smellnone
This is a fantastic example of how flowers evolve specifically to suit their pollinator’s needs (and likely vice-versa.) Flowers also attract pollinators by shape and nutrients that suit their needs. For example, flowers pollinated by bees often have “landing pad” shaped petals that the bees can rest on while obtaining pollen and nectar, they are also of a size and shape that allows the bees to fit their heads into the flower, but not be so big that the bee could fall in and become trapped. The way a bee’s vision evolved to see these yellow, white, and blue flowers so vividly is the easiest example for humans to experience this attracting method used by flowers.
So, other than nerding out over bee-sight, what makes this passage so awesome is that it is essentially a really deep bit of science mentioned in an introductory book about bees and beekeeping of all places! A Book of Bees is not where I would expect an author to bring up the research of Dr. Eric Erickson. And that is seriously cool. I know a lot of people who think beekeeping has nothing to do with science, but this passage, and a few others from this book reveal that the average beekeeper’s mind is actually very keen on not only the biology of bees, but the sociology, immunology, and even literature about bees as well. This is something that has definitely increased my own interest in bees and beekeeping.
I think Sue Hubbel’s A Book of Bees is a book that should be on the reading list for anyone curious about bees or beekeeping because it covers such a broad range of subjects such as literary, scientific, and practical matters. If you already know a good deal about bees, pick it up anyway, it may spark a new interest in this fascinating little insect.

Bee evolution driven by flower colour

Many readers may have wondered which came first; the chicken or the egg, but a similar problem occurs when trying to decide who led who in plant bee evolution. Well now, the problem has been solved – at least in Australia. 
A team of researchers in Australia has shown that the evolution of flowers in that country was driven by the preferences of bees, rather than the other way around. In their paper published in the Proceedings of the Royal Society B, the team describes how they gathered over a hundred samples of different flowers and then compared them against the types of colours that bees
best identify and then compared those results with research findings regarding bees and flowers in North America.
The research teambegan their study based on research already conducted by other scientists looking to find connections between bees and flower colours in North America. There researchers have found a close connection between flower colour and the kinds of colours bees are able to see, and what attracts them. Then because Australia has been isolated from the rest of the world for millions of years, the team theorized that if the same colour patterns emerged independently in such a place, it would prove that the flowers in both places adapted to the bees, and not the other way around. Helping out was prior research that showed that not long after Australia broke away from the other continents some 34 million years ago, the flowers blooming on the island were bland and nearly colourless; which gave the researchers a unique opportunity for learning about how colouring in flowers comes about, as today, Australia is teaming with a huge variety of brightly coloured flowers.
The team collected flower samples from 111 native species then studied them using a spectrophotometer (a device that measures different properties of light over a given spectrum). In so doing they found that the flowers displayed colours that matched almost exactly with the blue and green ultraviolet vision receptors in bees.
And because the results matched those found in North America, the team concluded that the flowers in both places co-evolved in the same way, thus proving that the flowers were reacting and adapting to what the bees were looking for, rather than the bees changing to help them better find the particular flowers that best suited them.
This new research also shows that because flowers have been adapting to suit the taste of bees, rather than for birds or butterflies, bees are the primary means by which flowers are pollinated, which means that as bee populations decline, so too will flowers, and perhaps their rich colouring.
 Flowering plants in Australia have been geographically isolated for more than 34 million years. In the Northern Hemisphere, previous work has revealed a close fit between the optimal discrimination capabilities of hymenopteran pollinators and the flower colours that have most frequently evolved. We collected spectral data from 111 Australian native flowers and tested signal appearance considering the colour discrimination capabilities of potentially important pollinators. The highest frequency of flower reflectance curves is consistent with data reported for the Northern Hemisphere.
The subsequent mapping of Australian flower reflectances into a bee colour space reveals a very similar distribution of flower colour evolution to the Northern Hemisphere. Thus, flowering plants in Australia are likely to have independently evolved spectral signals that maximize colour discrimination by hymenoptera. Moreover, we found that the degree of variability in flower colouration for particular angiosperm species matched the range of reflectance colours that can only be discriminated by bees that have experienced differential conditioning. This observation suggests a requirement for plasticity in the nervous systems of pollinators to allow generalization of flowers of the same species while overcoming the possible presence of non-rewarding flower mimics.
The photo of the flower, shows a photographic reconstruction of how bee vision would see a flower, which appears yellow to human eyes.
Reference: Journal reference: Proceedings of the Royal Society B.

How flowers appear to bees

How bees see flowersBees can see colours but they perceive the world differently to us, including variations in hue that we cannot ourselves distinguish. Now, in some fascinating research,  scientists at Queen Mary and Imperial college, University of have developed ‘FReD’ — the Floral Reflectance Database—which holds data on what colours flowers appear to be, to bees. The development of the catalogue, which has involved a collaborative effort between researchers at two Schools at Queen Mary is reported in the journal PLoS ONE.
The work addresses the existing issue that records of flower colours do not take the visual systems of pollinator insects into account. Bees—for example—have evolved completely different colour detection mechanisms to humans, and can see colours outside our own capabilities in the ultra-violet range. Professor Lars Chittka from Queen Mary’s School of Biological and Chemical Sciences said:
“This research highlights that the world we see is not the physical or the ‘real’ world—different animals have very different senses, depending on the environment the animals operate in.”
His team have measured the spectral reflectance of a number of flowers in different locations and analysed what bumblebees perceive, including different shades of ultra-violet. They have created a database in which the colours of flowers are indexed from this vitally important pollinator’s point of view. For the first time, this database will allow them to analyse global trends in flower colour, for example how flower colours might change in areas with high UV radiation. The team believes that there are many possible applications for scientists from different fields.
Co-author Professor Vincent Savolainen, from the Department of Life Sciences at Imperial College London, who holds a joint post at the Royal Botanic Gardens, Kew, adds: “We hope this work can help biologists understand how plants have evolved in different habitats—from biodiversity hotspots in South Africa to the cold habitats of northern Europe. FReD’s global records may show how flower colour could have changed over time, and how this relates to the different insects that pollinate them, and other factors in their local environment.”
How bees see flowersSamia Faruq from the School of Electronic Engineering and Computer Science is assisting Professor Chittka on an EPSRC funded PhD studentship, and is an expert in the computer modelling side of the project: “FReD provides over 2000 records with the colours that the bee sees presented in a very simple way. A successful flower has to be ‘noticed’ by the bee, and FReD provides a better understanding of the strategy flowers attain.
Colour patterns emerging from the location or altitude in which flowers are found may in turn increase our understanding of the plant-pollinator relationship. They will also be able to determine if flower colours in a given location are converging or diverging in order to give themselves the best chance of reproducing.
Professor Peter McOwan, a computer scientist who helped in developing the technical side of the project, commented: “This combination of biology and computer science, allowing scientist to collaboratively access important data in new ways shows the power of combining these two scientific disciplines. This interdisciplinary approach can produce significant new applications that will help make a real impact in better understand the natural world.” The database is freely searchable and open for international contribution, and will inform future ecological studies. “The records can be used to link flowers together by colour, although they appear different to us. On a global scale we will be able to identify the colours preferred by pollinators and see how this varies. This is very significant in terms of the global food supply, which relies on these insects and bees in particular” added Professor Chittka.
Source: Queen Mary, University of London.
Sarah E. J. Arnold, Samia Faruq, Vincent Savolainen, Peter W. McOwan, Lars Chittka. FReD: The Floral Reflectance Database — A Web Portal for Analyses of Flower Colour. PLoS ONE, 2010; 5 (12): e14287 DOI:10.1371/journal.pone.0014287