How to evaluate the characteristics of bee colonies?

The New Year has started with a new commitment to beekeeping - to implement a system for assessing bee colonies in practice. As with any commitment, it requires consistent implementation and a clear understanding of what we want to achieve or the goal of this assessment system. The goal is to obtain objective results on the performance of bee colonies during the season, to select the best bee colonies from which to breed material (queen bees, drones) and develop the characteristics of certain bee colonies for future crossbreeding. As mentioned in a previous article (December 2021 "Beekeeper"), to reduce the influence of external environmental factors on the characteristics of bee colonies, it is necessary to perform selection work at the local level to achieve the best possible results. Implementation of an assessment system is one step towards this direction. For the system to work in the long run, it must be simple, easily repeatable, and not labor-intensive, considering that beekeepers are usually especially busy in the summer. To avoid confusion in the records made during the season, the system requires clear evaluation criteria and convenient recording methods. Basic requirements for evaluation: 

• Choose 3-6 important characteristics to include in the evaluation system. 
• Prepare a convenient observation sheet. 
• Evaluate at least 10-15 bee colonies in one apiary to understand the influence of weather and apiary location on the results. Use average indicators of apiaries to compare differences between different apiaries [1]. 
• One person should evaluate one characteristic in one apiary for all test colonies in one day to increase the objectivity of the results [1; 2]. If possible, evaluate multiple characteristics in one inspection. 
• Make careful records each time, including basic information about the apiary, the origin of the test colonies, the evaluation date, and even the weather. 
• Provide equal conditions for all test colonies during the season, feed and expand them equally, do not divide them, provide the same type of hive, etc. 
• Begin evaluating a newly created colony after 40 days when the worker bees have been replaced [1]. 

In the following, I will provide a brief overview of what could be evaluated and how the results could be compared.

1. Development of the bee colony. By the seasonal development of the colony, that is, the size of the bee population (colony strength) and the amount of brood, it is possible to determine how the colony has adapted to wintering and how quickly it develops in the spring. Large and strong colonies are one of the prerequisites for a larger honey and pollen yield, as well as maintaining a healthy microclimate in the colony, which helps to prevent disease outbreaks.

1a. Colony strength (number of combs). The bee colony is assessed at least three times a year: before winter in the autumn, in early spring, and in the summer. Remove the roof and count the number of combs inhabited by bees, while fully inhabited combs are counted as 1 and partially inhabited combs are counted proportionally as 0.25, 0.5, 0.75. If the colony inhabits not only the brood chamber but also the honey supers, count the inhabited combs of those supers as well. Since all test colonies must have the same type of hive with equal volume and size, the inhabited combs of both the brood chamber and the honey supers can be counted together and recorded on the observation sheet [1; 2]. If the comb size in the honey supers differs from that in the brood chamber, note the type of comb as well.

1b. Brood quantity (number of combs). The brood quantity in the colony is assessed at least four times a year: in autumn, in early spring, 6 weeks after the first spring inspection, and in the summer. During the colony inspection, count the number of combs with brood and record the result on the observation sheet. If the brood is only on one side of the comb, count it as 0.5 combs. If the brood is the size of a tennis ball, count it as a comb of brood [2].

2. Honey yield (kg). During the season, when collecting honey, record from which colonies the honey supers were removed from. Weigh the supers before and after extracting the honey, and record the weight difference as the weight of the extracted honey on the observation sheet for the corresponding colony. If honey is extracted multiple times during the season, add up all the results for the extracted honey for each colony. Only honey collected in the honey supers is evaluated. Weighing scales with a precision of 0.1 kg are recommended for weighing [1; 2]. If weighing the supers is physically impossible, an alternative method of keeping records is to count the number of combs with honey in the colony. By knowing the average weight of honey in one comb and the number of combs, it is possible to calculate the approximate kilograms of honey obtained from a particular colony. Of course, such a calculation will not be precise, but it can be useful for relative comparison of colonies.

3. Tendency for swarming (1-4 points). Although swarming is a natural mechanism for the reproduction of bee colonies, for beekeepers, it results in a decrease in the strength of the colonies left behind, loss of good bee queens, and a significant loss of bees. Sometimes, there may be a small colony in the hive with such a pronounced swarming tendency that it swarms repeatedly throughout the season despite all the beekeeper's efforts. If swarming causes concern, it can be included as an important criterion in the evaluation system. In such cases, during the typical swarming period (May, June), colonies should be inspected every 7-9 days, and their swarming tendency should be assessed on a point scale from 1 to 4, choosing the most appropriate description for the situation (if necessary, a more precise assessment can be given using 0.5 points):

• 1 point - the colony swarmed, but it could have been prevented by creating a nucleus.
• 2 points - a strong swarming tendency is observed, bee queen cells are repeatedly removed, the number of open cells is reduced, the queen is getting smaller, and bees do not build new cells.
• 3 points - a low swarming tendency is observed, there are few queen cells, and no other signs. Swarming can simply be suppressed by expanding the nest and removing the queen cells.
• 4 points - no swarming tendency is observed, and there are no sealed queen cells [1; 2].

Note that the supersedure queen cells or the emergency queen cells are not considered swarming in this evaluation.

4. Aggressiveness-gentleness or defense reaction (1-4 points). As the number of bee colonies in the apiary increases, the time devoted to each colony inspection decreases. In order to perform inspections quickly and pleasantly, it is crucial that bees are tolerant and not aggressive. The behavior of the bees should be evaluated at least 3-6 times per season regardless of the weather conditions [1]. Decide whether to start inspections with or without smoke for all colonies, and follow this practice consistently. Change the order of inspecting colonies each time, as they are very sensitive to the mood of their neighbors and can become more aggressive. If bees become disturbed during an inspection due to a moment of inattention (e.g., dropping a frame or dropping a tool into the hive), record this incident and evaluate it. During inspections, assess the aggressiveness-gentleness level of colonies on a point scale from 1 to 4, choosing the most appropriate description for the situation (if necessary, a more precise assessment can be given using 0.5 points):

• 1 point - during inspection, several bees fly and sting despite smoke, even without opening the hive.
• 2 points - several bees fly and sting, but only after the hive is opened and inspected.
• 3 points - bees do not fly and sting, but exhibit defensive behavior, such as head-butting, hissing, or following the beekeeper.
• 4 points - bees do not exhibit any defensive behavior and are gentle [1; 2].

During the first inspection, if a bee colony displays strong aggression and makes inspection impossible, such a colony is immediately excluded from the evaluation system.

5. Nervousness-calmness (1-4 points). If it is necessary to find the queen bee during the inspection, it can be difficult and time-consuming if the bees are very nervous and form clusters in corners of the hive. It is also more difficult to carefully put the frames back into the hive with such clusters. The degree of nervousness-calmness is evaluated 3-6 times during the season regardless of the weather. During the inspection, the bee colony is evaluated on a point scale from 1 to 4, choosing the most appropriate description of the situation (if it is necessary to indicate more precisely the differences between bee colonies, a 0.5 point can also be used):

• 1 point - bees behave nervously, leave the comb, run to the edges/corners of the hive, and build clusters inside or outside the hive.
• 2 points - some bees leave the comb, while others form clusters in corners and on the edges.
• 3 points - bees move around, do not leave the comb, and do not form clusters.
• 4 points - bees sit calmly on the comb and do not react to the beekeeper's presence [1].

6. Disease resistance. Every bee colony is susceptible to varroa mites (Varroa destructor), and uncontrolled infestations weaken and destroy bee colonies. The long-term solution is to select bee colonies that show more pronounced hygienic behavior and better resistance to the varroa population in the colony. The powdered sugar method can be used to monitor varroa infestations in adult bees, while the needle test can be used to evaluate hygienic behavior. Both methods are not labor-intensive, time-consuming, have low costs, and are easily repeatable, ensuring the reliability of the results [3].

6a. Adult bee infestation with varroa mites (number of mites on 10g of bees) - powdered sugar method. This method can be performed and results obtained immediately in the apiary. The test should be performed at least 3-4 times during the season (early spring, before mite treatment in summer, after treatment in autumn, and if possible, before overwintering). The following items are needed to perform the test: powdered sugar (250 g is enough for 7 colonies), tablespoon, kitchen scale, 40x40 cm plastic sheet, at least 120 mL plastic container with lid for collecting and weighing bees, at least 750 mL plastic container with lid and fixed metal mesh at the bottom (mesh size 2.8 mm) for performing the test, a very fine mesh (mesh size 1 mm), and a light-colored container.

• Remove the frames from the hive, shake the bees onto the plastic sheet, skillfully roll them in the container intended for weighing, weigh them and transfer them to the plastic container with the mesh. It is necessary to weigh about 50 g of bees, which corresponds to approximately 500 bees.
• Reverse plastic trays with bees with the mesh facing up, through which 5 tablespoons of powdered sugar are poured. Leave the bees in powdered sugar for 3 minutes, shaking the tray gently from time to time.
• Reverse the plastic trays with the bees and sieve the sugar and mites through a fine sieve placed in the tray. After sifting, return the bees to the hive.
• Sift the powdered sugar through the fine sieve in the tray. Dump the contents of the sieve onto a bright surface and count the mites.
• Calculate how many mites are on 10g of bees with the formula: number of mites * 10 / bee mass (g) [2].

More information on alternatives to the powdered sugar method with pictures can be found in the brochure "Recommended methods for limiting varroa in bee colonies" by the Latvian Beekeeping Association, updated in 2021 [4].

6b. Hygiene behavior (needle test - number of uncapped brood cells). This test should be performed at least twice a season, in good weather, but not during the active nectar and pollen collection period. If the colony has been recently established, the test can only be performed after 40 days, when the worker bees have been replaced. To perform the test, you will need the following items: a wooden, metal, plastic, or cardboard template that matches a 10x10 cell area, entomology needles (size no. 2, length 40mm, diameter 0.38mm - intended for medium-sized insects), and a marker.

• Find frames with capped worker bee cells in which the larvae have white or pink eyes. Select a cell using the needle and check the age of the larvae.
• Place the template over the cells and mark the first and last cells in a 100-cell area with a marker to determine the template's position (see Figure 1).
• Pierce 50 capped cells, starting from the 2nd cell in the row from left to right in the 100-cell area. Pierce through the cap and direct the needle towards the bottom of the cell. There may be empty cells or cells with pollen or nectar in the 100-cell area, so these cells should be skipped. After piercing the necessary 50 cells, color the 51st cell with a marker to indicate the end of the test area (see Figure 1).
• Mark the side of the hive where the test was performed on the test frame and return it to the hive.
• After 6 hours, check the results and count only the capped cells that have been uncapped between the marked 1st and 51st cells [2].
• Calculate the number of uncapped cells in 6 hours by subtracting the number of capped cells from 50 [3].

Figure 1.  Hygiene behavior by needle test (author by [1; 2]).

Processing and Comparison of Results. The results of the evaluation of all previously described characteristics are expressed in different units: number of frames, kilograms, points, number of mites per 10 grams of bees, number of capped cells. From the obtained results, it is clear that a higher result indicates better performance (except for the level of mite infestation), but counting these indicators together is not allowed. To obtain mutually comparable results between the characteristics and the overall performance result of the colony, where all evaluated characteristics have equal weight or importance, result processing is necessary (see Table 1):

• For each characteristic, calculate the average arithmetic result (A) separately. For example, add up all the points obtained for the tendency to swarm and divide by the number of evaluated colonies.
• The obtained average result for each characteristic is the apiary’s average result, which is equated to 100% (B). These 100% are used as the threshold value for comparing colony performance.
• Express the individual result of each colony in percentages (D): multiply the colony's result (C) by 100 (B), divide by the apiary’s average result (A). The exception is the level of mite infestation, where the formula is different: subtract the individual result of the colony (C) from the average result of the apiary (A), multiply by 100 (B), divide by the average result (A), and add 100.
• Calculate the average performance of each colony in percentages by adding up all the characteristic evaluations in percentages and dividing by the number of characteristics (n). If the colony's result is higher than 100%, for example, 127%, then the colony's performance is 27% higher than the average of the colony. If the colony's result is lower than 100%, for example, 85%, then the colony's performance is 15% lower than the average of the colony. This comparison can also be made for each characteristic separately [5].

Table 1. Example of bee colony characteristics evaluation results (author)

After processing and comparing the results, the top-performing colonies are obtained, which can be used for breeding queen bees and drones and for obtaining the next generation. If any of the given characteristics are important to you in your colony, dare to try and evaluate them throughout the season! I wish everyone to fulfill their New Year's resolutions in beekeeping!

References:

• [1] Büchler, R., Andonov, S., Bienefeld, K., Costa, C., Hatjina, F., Kezic, N., ... & Wilde, J. (2013). Standard methods for rearing and selection of Apis mellifera queens. Journal of Apicultural Research, 52(1), 1-30.

• [2] Uzunov et al., (2021) Book of Methods for Performance Testers, EURBEST project (AGRI-2017-0346), Bee Institute in Kirchhain, Germany (English language version).

• [3] Büchler, R., Kovačić, M., Buchegger, M., Puškadija, Z., Hoppe, A., & Brascamp, E. W. (2020). Evaluation of traits for the selection of Apis Mellifera for resistance against Varroa Destructor. Insects, 11(9), 618.

• [4] Eglīte I. (2021). Ieteicamās metodes varru ierobežošanai bišu saimēs. Papildināts izdevums Jura Šteiseļa redakcijā. Pieejams: https://www.strops.lv/attachments/article/66/varra_2021.pdf (LBB mājaslapā/sadaļa Raksti/Brošūras)

• [5] BeeBreed.eu (2021). Manual of BeeBreed. Bee institute Hohen Neuendorf. 29.10.2021. Pieejams: https://www2.hu-berlin.de/beebreed/ZWS/do/en/manual.pdf

Published in the journal "Biškopis", the first issue of 2022, published by the Latvian Beekeeping Association."