Current and Future Management Strategies for Varroa Mites

Transcription

1 Current and Future Management Strategies for Varroa Mites Ramesh Sagili

2 Overview of Honey Bee Research Projects at OSU Honey Bee Nutrition Nosema ceranae Effects of Pesticides Applied studies on Varroa control

3 Resting Worker Bees

4 How many of you lost significant number of colonies past winter? What factor or factors do you think was/were responsible for your colonies' demise? How many of you monitor Varroa levels in your colonies? How many of you use Varroa mite treatments? How many of you think Varroa mite is a problem or responsible for your colony loss?

5 Varroa mite life cycle First egg after 70 hours and subsequent eggs at 30 hour intervals (DM Caron)

6 Female Male

7 PMS (parasitic mite syndrome) Virus transmission: DWV, IAPV, KBV, CBPV, BQCV Before arrival of Varroa, viruses were considered a minor problem. Varroa is responsible for direct injection of virus particles.

8 PMS

9 In Apis cerana, Varroa is unable to reproduce in worker brood Varroa History of Varroa mite Why Varroa is a greater menace of European honey bee but not for the Asian honey bee? Host-parasite relationship Natural selection is a long process to get the resistance or tolerance

10 Bee Informed Partnership Survey Beekeepers who reported using treatment for Varroa lost 26% fewer colonies than those that did not use a mite treatment.

11 Reasons for Colony Losses 2010 Queen failure (30%) 2011 Queen failure (29%) Mites (24%) Starvation (21%) Starvation (17%) Mites (16%) CCD (13%) CCD (12%)

12 Madras, OR Sampling Results: Varroa mite levels Percent Infestation First week of July Time Last week of July

13 Varroa IPM In Honey Bee Colonies

14 IPM Combination of various available control methods both chemical and nonchemical. Periodic monitoring of mite levels

15 Varroa mite economic threshold levels ET is not universal ET depends on: geographic location, level of colony resistance to Varroa etc. ET range of mites/day (sticky board data) is suggested in the existing literature ET in terms of percentages (Alcohol wash): Spring / summer: > 1% Fall: > 3% Late fall / winter: > 10%

16 Honey bee and Varroa mite population dynamics Scientificbeekeeping.com

17 Of course don t get the mite loads to this level!!

18 Varroa mite treatments should not be calendar based but based on realistic mite population levels. Early brood rearing means early mite control strategies to be implemented.

19 Treatments Synthetics (Organophosphates, Synthetic pyrethroids) Organic chemicals

20 Amitraz (Apivar) Contact miticide 2 strips per brood chamber Degrades relatively faster (3-4 weeks)

21 Some important considerations when using Apivar Results can be variable depending on factors such as: Dose and placement of strips. Appears to decrease mite populations gradually. Using in spring may be the best option. Risk of resistance development...resistance development can be delayed following removal directions and rotating with other available options.

22 Thymol (slow release gel) Apiguard Temperature dependent (60-100º F) Also active against tracheal mites

23 Treatment % age decrease in brood (uncapped + capped) Mite mortality 50 gm on top with spacer gm in middle with spacer gm on top without spacer gm in middle without spacer gm on top with spacer gm in middle with spacer gm on top without spacer gm in middle without spacer No Queen loss observed in any of the experimental hives

24 MAQS and Hopguard Mite-Away Quick Strips (MAQS) HopGuard

25 Mite-Away Quick Strips (MAQS) Formic acid (46.7%) Recommended dose: 2 strips per treatment Treatment period: 7 days Temperature range: 50-92ºF Colony size: colony cluster covering a minimum of 6 brood frames Excessive temperatures (>95ºF can cause excessive brood mortality and absconding) Kills male and female mites in capped cells (advantage: mite reproduction is restricted) (is there a problem in pupal development?)

26 Efficacy of MAQS, Apiguard and Hopguard Infestation level after treatment (percentage of mites) MAQS Apiguard Hopguard Control Treatments

27 Oxalic Acid 3% Oxalic acid sprayed 3-4 ml per comb side killed 98% mites. Ideal when colonies are broodless (Nov or Dec). Not registered for use in The U.S.A.

28 Cultural Methods (Non chemical treatments) Drone comb traps Screened bottom board Powdered sugar dusting

29 Other strategies to reduce mite reproduction Small cell foundation -may be we will increase additional cycle of brood providing mites more opportunity to breed -also may be putting selective pressure on mites to develop faster (reduce life cycle) Creating intermittent brood less periods

30 Biological Control Predatory Mite: Stratiolaelaps scimitus Stratiolaelaps scimitus is a soil dwelling predatory mite Currently used for controlling Fungus gnats and thrips.

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33 10 Treatment Colonies 10 Control Colonies Control Colony Predatory Mite Treatment Colony

34 Mites with damaged appendages Mite with no damage

35 Future Strategies for Varroa Control RNAi (interference) Gene knockdown or gene silencing and stop protein expression (done by synthesizing a doublestranded RNA). DNA.mRNA.rRNA (directs the translation of mrna in to proteins). dsrna impairs translation of viral proteins-reduces viral replication. May be a therapeutic alternative in the future.

36 Questions???