Timing of varroa control & bee and colony survival in winter

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Camiel Hendrickx
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1 Timing of varroa control & bee and colony survival in winter Tjeerd Blacquière, Lonne Gerritsen, Sjef van der Steen & Bram Cornelissen

2 Intro brood cell infestation with varroa: lower protein more virus infections reduced life expectancy Normal expectancy: spring summer winter days days >140 days short lived winter bees: early spring death

3 intro Healthy young bees: diseases: low or now infestations good condition/shape nutrition: plenty of good (and diverse) pollen plenty and good royal jelly Good royal jelly if: Nurse bees are healthy and in good shape only true if one month ago: colony was healthy plenty of good food (pollen & nectar) available

4 Research questions 1. When are winter bees raised in NL 2. How long do they survive 3. Is individual bee survival affected by varroa infestation (timing of control) 4. Is colony survival affected by timing of varroa control

5 M&M Bee colonies treated against varroa before: 1. July 1 (and December 13: OA) N=6 2. September 1 (and December 13: OA) N=6 3. October 1 (and December 13: OA) N=6 4. not treated (only December 13: OA) N=6 Marking grey bees every fortnight from Aug- Nov count survivors every two weeks count number of sealed brood cells every two weeks Evaluate surviving and dead colonies in April

6 Results: mite fall mijtval beh 1 beh 2 beh 3 beh 4 10-aug 24-aug 7-sep 21-sep 5-okt 19-okt 2-nov gemiddelde mijtval per kast per dag 16-nov 30-nov 14-dec 28-dec 11-jan 25-jan 8-feb 22-feb 8-mrt 22-mrt 5-apr 19-apr

7 Mite fall mijtval per groep per dag (t) ( n m it e s )

8 Sealed brood cells cellen gesloten broed per volk aug 17-aug 24-aug 31-aug 7-sep 14-sep 21-sep 28-sep 5-okt 12-okt 19-okt 26-okt 2-nov groep 1 groep 2 groep 3 groep 4 gemiddelde

9 Sealed cells winter and gem 2005 gem 2006 # broed cellen aug aug sep sep okt okt nov 16- nov dec 11- jan feb mrt

10 Survival of cohorts hatched Aug Nov jul 10 aug 24 aug 7 sep 21 sep 5 okt 20 okt 2 nov 15-jul 15-aug 15-sep 15-okt 15-nov 15-dec 15-jan 15-feb 15-mrt 15-apr gemiddeld % overlevende bijen

11 Survival of cohorts hatched Aug Nov 06 behandeling aug 24-aug 7-sep 21-sep 5-okt 19-okt 2-nov 10 aug 24 aug 4 sept 21 sept 5 oct 19 oct 2 nov 19 nov 13 dec 11 jan 15feb 14 mrt 12 april

12 Survivors in April # surviving bees Aug-31 Aug 1 Sep-14 Sep 15 Sep-28 Sep 29 Sep-12 Oct 13 Oct-26 Oct 27 Oct-9 Nov treatment Survivers: number of sealed cells X Percentage of surviving marked bees

13 Colony losses and individual bee survival Group % lost colonies N bees from 2005, on April 19, 2006* Mean N bees per colony ** *** 4000*** * percentage recovered marked bees X number of brood cells before hatching period ** counted (estimated) bee numbers present on April 19, 2006 *** only surviving colonies

14 Colony losses 2 nd experiment Colonies lost April 4, 2007: Group 1: 0 % (N=7) Group 2: 0 % (N=6) Group 3: 0 % (N=6) Group 4: 30 % (N=10)

15 Conclusion Results Winter bees raised in September November Timing varroa control: early control (before July): no losses intermediate (August): no losses, but more decline bees late control (Sept): some colonies lost, bees decline faster no control until Dec: most / many colonies lost, strong decline bees in surviving colonies late control longer brood production, later winter bees Similar results in survey Dutch beekeepers: less losses when controlling varroa early Focus on varroa control Focus on Bee Quality (proteins age cohorts)

16 Thank you Wageningen UR

17 M&M: many bees lost in a few days 90% 80% 70% 60% 50% 40% 30% roze blauw geel paars wit 20% 10% 0% 2 dagen 1 week 2 weken 3 weken 4 weken 5 weken 6 weken 7 weken

18 april 15-mrt feb 19-okt 2-nov 16-nov 13-dec 11-jan behandeling okt 20-sep 6-sep 29-aug 9-aug # broodcells

19 Experiments 2008 Survey bee health status Dutch beekeeping 150 bee keepers all over country coordinated by and beekeepers organizations 5 colonies sampled on each apiary sample bees from first frame samples split in the lab: determinations made in NL and UK (bijen@wur, CVI Lelystad, Central Science Lab York)

20 Experiments 2008 ctnd Determinations on bees: varroa AFB, EFB Nosema (apis & ceranae) viruses: KBV, DWV, BQCV, SBV, CPV, APV, IV Chalk brood Stone brood Acarapis woodi (heavy metals) Honey samples pollen spectrum

21 Experiments 2008 & further Relation between varroa infestation rate and other pathogens (viruses, AFB,...): experiments Natural selection varroa resistance Island approach nukes (every year new set up from surviving colonies) varroa development in worker brood no Bond Protein research (shown by Van der Steen)

22 Aim sustainable and disease preventing beekeeping good beekeepers practice (extension and education) Eventually: no colony losses

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