COLOSS - VARROA CONTROL TASKFORCE, BROOD INTERRUPTION STUDY 2016/2017

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1 COLOSS - VARROA CONTROL TASKFORCE, BROOD INTERRUPTION STUDY 2016/2017 Developed and photo by: Antonio Nanetti 1, Ralph Büchler 2, Aleksandar Uzunov 2, Ales Gregorc 3 1 CREA - Consiglio per la Ricerca in Agricoltura e l Analisi dell Economia Agraria, Unità di Ricerca di Apicoltura e Bachicoltura (CREA API, Via di Saliceto 80, Bologna, Italy. 2 Landesbetrieb Landwirtschaft Hessen, Bee institut Kirchhain, Germany. 3 Agricultural institute of Slovenia, Slovenia and Mississippi State University, South MS Branch Experiment Station, Poplarville, MS, US. PROTOCOL NO.1: BROOD INTERRUPTION FOR VARROA CONTROL Motivation In warm countries and in global warming scenarios, the long reproductive season causes high summer infestations. The available acaricides are often insufficient. A combination between a chemical treatment and a biotechnical practice was then developed. Principle High efficacy on phoretic but not on reproductive Varroa mites makes oxalic acid mainly fit for winter treatments (with broodless condition). The technique of this protocol brings mites to phoretic stage, and exposes them to the oxalic acid treatment. Practice Queens are caged for 25 days to obtain broodless colonies. Oxalic acid solution is administered thereafter by trickling, according to the method used in winter. Concentration is: oxalic acid 4.2%, sucrose 60% 1. Trickle 5ml/comb with bees (for Dadant-Blatt, Langstroth, AZ and other hive types) perpendicular to comb direction (left to right and vice versa if combs are parallel to flight direction). Expected efficacy, tolerability, side effects According to repeated tests in Northern and Southern Italy, efficacy is 95% or better; acute mortality is similar to controls; colony overwintering is similar to the controls; colonies usually show healthy, with clean cells, new wax and bees looking young; overwintering is as successful as controls. Decrease in honey harvest is not expected, but research is needed on this aspect. Environmental conditions (nectar flow, temperature, drought etc.) are not expected to play major influence. Colony conditions Until now, the available data and experiences refer to fully developed colonies in summer. Nuclei have not been taken into consideration so far. Amount of labour Caging is the critical part: minutes/colony or colonies/day (depending on beekeeper s skill, hive construction, colony population, queen marking, supers in place etc.). Trickling takes 1-2 minutes/colony. 1 Api-Bioxal according to label or bihydrate oxalic acid, sucrose and demineralized water 1:10:10 in weight. ATTENTION: the use of Oxuvar or Ecoxal leads to insufficient concentration. 1

2 Period of the year The available data refer to summer. Indications of successful overwintering with late season applications have been obtained in Northern Italy. Additional material needed One cage (Var-Control, 5 x 7.5 cm) with queen excluder on both sides 2 must be accommodated in a slot cut below the top bar. Procedure Fix the cage in a comb. This frame can be left in the colony for re-use. Refer to the following pictures. Locate (1) and gently remove (2) the queen from the comb. Introduce in the cage (3), shut firmly (4) and leave untouched for 25 days. On day 25, unseal the cage (5) and reintroduce the comb into its slot (the queen finds her way out shortly). Administer the oxalic acid solution onto the combs (6). 1) Locate the queen. 2) Remove the queen. 3) Introduce in the cage. 4) Shut the cage. 5) On day 25: open the cap. 6) On day 25: oxalic acid administration. 2 The normal queen excluders used for supers (slots of 4.2 mm) occasionally let tiny queens pass through. These slots of 3.7 mm are safer: (a device for beekeepers not familiar with queen handling is shown as well). 2

3 Trial protocol: Experimental question Measure this method s efficacy and side effects in comparison to the usual treatments. Material - An apiary of at least 20 full size, naturally infested colonies. - Sticky sheets for counting varroa mites on bottom board. - Two strips Apistan and two strips Apivar per colony. Experimental design and colony conditions - Create two random homogeneous groups (random sampling without replacement): Treated and Control. - Field measures are taken to minimize drift and reinvasion. - Remove or pre-treat colonies not included in the trial. - Limit colony handling to strictly needed (for all colonies in the experiment). Do not affect natural bee population grow and brood development. Treatments In Group Treated, follow the above reported procedure: cage the queen on day 0, open the cage and administer oxalic acid on day 25. The oxalic acid efficacy is considered to be fully developed 7 days post treatment. In Group Control, treat as usually beekeepers do (but not with amitraz or pyrethroids). The treatment of both groups must finish the same day. Count fallen mites every 3-4 days in the 25 days caging period, daily during the 7 days oxalic acid period. Critical treatments Insert two Apistan and two Apivar strips in the centre of the colony, three combs apart, in cross. Remove two weeks later 3. Count fallen mites every 3-4 days. Side effects on the colonies Before caging, check all the colonies and measure adult population and brood area with the Liebefeld method. Repeat the measures one month after the treatment during prewintering period and next spring. In all colonies, take note of queen mortality/supersedure in the treatment period. If case a honey flow is likely to occur during the treatment, weight the colonies precaging and weight again post-harvest. Optional recordings Environmental recordings may be helpful to frame the trial correctly. If possible, take continuous recording of external and internal temperature and relative humidity (we use ibutton Hygrochron Temperature/Humidity Logger DS1923). Dead bee counts may be taken with traps placed at the hive entrance. 3 This treatment lasts 2 weeks instead of the 6 required by the labels. The shorter period is justified by: the first week, the brood is absent or scanty; shock effect is expected with the combination of two active substances; need to limit mite reinvasion; side effects of long term treatments with tau-fluvalinate and amitraz in combination are unknown. The procedure favours good efficacy estimate in the Group Treated, but may imply overestimate in the treated controls. 3

4 Usual treatment. This must finish the day +7 COLOSS - VARROA CONTROL TASKFORCE - BROOD INTERRUPTION STUDY 2016/2017 Efficacy The efficacy is calculated as follows: E% = Sum of mites dead from caging to strip insertion/sum of mites dead from caging to strip removal. Calendar of main activities DAY GROUP "TREATED" GROUP "CONTROL" BOTH GROUPS Miscellaneous Sticky sheets activities -26 Liebefeld check -25 Queen caging Insert sticky sheets -22 Count mites and change -18 Count mites and change -15 Count mites and change -12 Count mites and change -8 Count mites and change -5 Count mites and change -2 Count mites and change 0 Queen release Count mites and change Oxalic acid administration 1 Count mites and change 2 Count mites and change 3 Count mites and change 4 Count mites and change 5 Count mites and change 6 Count mites and change 7 Insert strips Count mites and change 10 Count mites and change 14 Count mites and change 17 Count mites and change 21 Remove strips Remove sticky sheets Liebefeld check prewintering Liebefeld check Next Liebefeld check spring 4

5 PROTOCOL NO.2: BROOD REMOVAL BY USING TRAPPING FRAME Introduction The method of brood removal is known to have significant impact on Varroa destructor population reduction in the colony of honey bees. The method is based on the fact that mite s reproduction is associated with the developmental stage of the workers and drones in the sealed brood. During this stage the mites are confined in the sealed brood cells. By removing the Varroa invaded sealed worker or drone brood the beekeepers can easily decrease the infestation level. The method s efficacy range from 70 to > 90%, nonetheless strongly depending from the used approach (worker or drone brood, trapping frame, additional chemical treatment of the adult bees or other combinations) and the colony s developmental stage (amount and ratio of open and sealed worker or drone brood). As the method can be used without any chemicals it is applicable during honey flow periods without any risk of residues. Removal of entire brood The removal of entire brood is one of the most radical biotechnical approaches to control Varroa destructor population in the colony. It is highly efficient, but may strongly affect overall colony performance. From the beekeeper s point of view it is labourintensive and requires additional equipment capacity. In this study we use the method of removal of entire brood with usage of trapping frame. Table 1. General information and requirements Colony s developmental Beekeeping season Nectar flow Period of the day Comments Brood production peak (preferably more sealed brood) 7-14 days before the honey harvest or at the latest immediately after the main honey harvest (6-8 weeks before ending of the main season). Preferable present (avoiding robbing during the manipulation of the frames and better colony development) Preferable in afternoon (as a measure for preventing robbing) Labour intensity Time demand Additional equipment / queens Feeding Assistance from skilled person is useful 7-10 min/colony ( 4 hours for 20 colonies) - 1 (single hive body) hive without frames for each operated colony - frames with drown comb or comb foundation - optionally new queen for nuc establishment Without regular nectar flow there is need for colony feeding with 2-3 liters/colony/week (first 3 weeks) 5

6 Procedure Step 1 Open the hive, find frames with brood combs (open and sealed), shake the bees from them (Fig. 1) and dispose all frames with brood combs in a new hive (Fig. 2) box or remove them for melting. Make sure that the queen remains in the original hive. Note I: for establishing a new colony with removed brood combs leave ca. 700 worker bees per comb (approximately open hand size from both sides) for warming the brood. The brood combs from different colonies can be put together in a new hive on 1 3 supers (10-30 frames). Those queenless units will rear an emergency queen if no selected queen is added by the beekeeper. Make sure that sufficient food combs are added to supply the bees for the next few weeks. The brood collector hive should be moved to a separate apiary to avoid robbery and mite exchange with the original hive. After days all the brood is gone and the bees can then easily be treated against Varroa. Note II: all brood from the original colony should be removed. Step 2 Insert frames with drown combs or foundations (Fig. 3) on the free places of removed frames. Leave free space for a single frame. Step 3 Insert a single trapping comb with plenty of open brood (preferably drone brood) but no sealed brood which might emerge before the trapping comb is removed from the colony. Close the hive. Note I: in case of intensive honey flow the suppers should remain on the hive. Step 4 After 7-9 days (Fig. 4), open the original hive and remove and destroy the trapping comb, now with sealed brood, add an empty comb or foundation to replace the frame with trapping comb. Note I: do not use the trapping comb with sealed brood under any circumstance Step 5 Without regular nectar flow (after the main honey harvest) there is need for colony feeding with 2-3 litres/colony/week (first 3 weeks). 6

7 Liebefeld method & 50 g bee samples Liebefeld method & 50 g bee samples Liebefeld method & 50 g bee samples Liebefeld method & 50 g bee samples COLOSS - VARROA CONTROL TASKFORCE - BROOD INTERRUPTION STUDY 2016/2017 STUDY DESIGN ( ) Groups and apiary At least 2 groups (Test and Control), with minimum of 10 colonies per group, should be established for comparison of the method. Alternatively, third group (Brood interruption) can be added from the aforementioned protocol. However, it is not recommended to keep more than 30 colonies on a single location. In a case of more than one location take care to evenly distribute colonies from all groups among the locations. I. Test group (Brood removal) - Colonies managed by the method of Brood removal II. Control group - Colonies managed by common local beekeeping practice III. Brood interruption group - Colonies managed by the method of Brood interruption Data collection The estimation of colonies strength (brood area and adult bees population) should be done by Liebefeld method. The recommended periods for colonies inspection are: 1. Shortly before the treatment (method) application 2. A month following the treatment (method) application 3. Before wintering and 4. Early spring in the following year During the inspections a sample of minimum 50 g of bees/colony should be collected 4 for estimation of Varroa infestation by the Washing method 5 or Powdered sugar method 5. After the removal from the colonies, the trapping combs (Brood removal group) should be examined for Varroa infestation in brood 5. Varroa treatments Summer treatment Winter treatment I. Test group (Brood removal) No additional treatment No treatment 6 II. Control group Common treatment (by region) No treatment 6 III. Brood interruption group According to the Protocol 1 for Brood interruption Time frame season (periods variable by region) JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR Brood removal 4 Collect bees from outer frames of the uppermost box. 5 For additional information please see (Dietemann et al., 2013 Standard method for varroa research, COLOSS Beebook, Volume II) 6 In case of winter treatment use Oxalic acid and count mite mortality for period of 3 weeks following the treatment 7

8 ANNEX Fig. 1 Removal of frame with open and sealed brood. One open brood frame is placed in the centre and remains as a trapping comb. Food combs without brood can remain at both sides. Fig 2 Establishment of new colony with opened and sealed brood with some bees. Fig. 4 Colony situation one week after brood removal: frames with foundation are drawn and the new brood nest is growing. Fig. 3 Insertion of frames with foundation in the original colony. 8