Lithium Chloride: Is it the next mite treatment?

 

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This colony eventually collapses due to extensive mite damage. It had all the major signs of mite damage.

Varroa continues to devastate colonies, and the issue seems to worsen as the years pass. For example, colonies with 5 mites per 100 bees in the spring would live 10 years ago, but now colonies seem to need to have < 1 mite/ 100 bees to survive. This is because of viruses. Mites transmit not only more viruses, but the viruses have become more virulent over time, such as Deformed Wing Virus. Researchers are finding new variants of Deformed Wing Virus that are more devastating, but Deformed Wing Virus phenomenon is likely just the beginning. As mites transmit more and different viruses, the mite issue will worsen.  As mite issues worsen, more and more control is needed.

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Honey bee with Deformed Wing Virus, the most devastating mite transmitted virus to date.

Beekeepers use many different forms of varroa treatment, and it really depends upon the “type” of beekeeper. Most commercial beekeepers use synthetic treatments such as amitraz, whereas hobbyists typically use organic treatments such as apiguard, formic acid and oxalic acid. While these treatments can be effective when used properly, they all have certain limitations. For example, apiguard and formic acid have temperature limitations, while mites can develop resistance to amitraz. As of now, there is not a perfect treatment. Each treatment has its time and place, however, “perfect” time rarely occurs. This is why many commercial beekeepers have struggled, and have accrued high annual losses. Think about it this way. Hobbyists can monitor and treat accordingly, whereas commercial beekeeper must treat their entire operation without knowing where their numbers lie. If a colony has high numbers after the treatment, then that colony is effectively dead. Beekeepers do not have time to manage each colony, so they must account for these “mite bombs” in their operation. Most treatments only work perfectly if the weather is warm or humid enough, the colony is a genetic predisposition against mites, and if the treatment is applied correctly. These are limitations that impact beekeepers because: A) they must constantly train new crew members, B)they often have a short window to treat due to migration, and C) they must treat 2000-20000 colonies. Because many treatments have limitations, these mite bombs can be scattered throughout the operation. This leads to “typical” 20-30% annual losses, even if the beekeeper does treat. This is why a new treatment option would help, and why I was excited to hear about lithium chloride.

 

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Varroa mite

Nature recently published a paper from researchers in the University of Hohenheim in Germany about Lithium Chloride, a possible new mite treatment. As I read about Lithium Chloride, I was left excited, yet curious about further experimental trials. Lithium chloride is new and exciting, especially because new varroacides are not produced regularly. I sample >30 commercial beekeepers annually, and they struggle with mite controls and which treatments. They often use amitraz, the main ingredient of apivar, which most beekeeper view as a “ticking time bomb” because beekeepers believe resistance is inevitable. Most commercial beekeeper experience 70-90% losses in the early to mid 2000’s because mites became resistant to coumaphos and fluvalinate, two major mite treatments at the time. This includes the commercial beekeeper I worked for whom lost 80% of his colonies in 2006 when mites became resistant to coumaphos. If lithium chloride has realistic potential, then beekeepers have an option IF mite become resistance to amitraz, the current #1 treatment for mites among commercial beekeepers.

 

Lithium chloride is a salt commonly used as a mood stabilizer in humans. It is often prescribe as psychiatric medication for treating major depressive disorders. I have taken a lithium chloride supplement before and it does work as a mood stabilizer. While lithium chloride does positively impact humans, lithium chloride has hardly been studied on insects. In reality, the effect of lithium chloride on insects is fairly a mystery. Because of this, I was skeptical about their experimental design and approach. However, they seemed to stumble upon Lithium Chloride through alternative studies, and that “surprisingly lithium salts mediate a strong acaricidal efect on Varroa mites”.

Image result for lithium chloride antidepressant

Does lithium chloride have potential? Sure. I would be ignorant if I said it may have potential. I mean, they clearly showed that feeding Lithium chloride to bees: A) kills mites and B) does not hurt bees. I cannot deny the results. However, they must be taken with a grain of salt for a few reasons:

  1. The study used caged bees and broodless artificial swarms. This was a great first start, but hardly replicates a colony setting.
  2. The study did not include brood, only phoretic mites. Powdered sugar has been shown to knock mites off bees, but I would NEVER use powdered sugar as a mite treatment. So while positive results exist, many factors must be considered.
  3. The mechanism is unknown. To truly understand the effectiveness, researchers must understand the mode of action. The mode of action is not everything, but it is definitely something, especially when performing studies on a colony level.
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This graphic shows survivorship of varroa mites when bees are fed different concentrations of lithium chloride. Mites died more readily when bees were fed the highest concentration.

I do not mean to bash lithium chloride because it has a lot of possibilities. Lithium chloride is easy to apply, most likely does not leave residues in honey or wax, and may kill >90% of mites, so I am all for Lithium chloride. But let us wait and see, because we have seen miticides like this before. Like the researchers said, lithium chloride provies a “promising basis for the development of an effective and easy-to-apply control method for mite treatment”. I sure hope so!

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This graphic compares honey bee survivorship when fed different concentrations of Lithium chloride. As you can see, the supplement did not effect bee survivorship by alot.

 

Cheers!
Garett Slater

 

 

The signs of mite damage- How to identify progressed varroosis

Varroa infested colonies entered the United States in ~1987, and changed beekeeping forever. Beekeeping has always been time consuming, difficult and experience oriented; however, beekeeping became even more challenging when beekeepers were called to eradicate a bug on another bug. Since its introduction in the US, beekeepers have reported high annual colony losses due to mites. In fact, some beekeepers report 60% losses due to this troublesome pest. While beekeepers have faced devastating challenges before, including American Foulbrood, Varroa mites has presented damages never before seen.

Varroa have become more difficult to manage since their introduction. The mites are seemingly embedded within the honey bee industry reality as nearly, if not all, colonies have Varroa. Like many beekeepers say: ” all my colonies have mites, I just cannot see them”. Even if alcohol washes do not reveal mites, Varroa is present in the brood or will be present soon due to infestation from surrounding colonies. As mites have become more widespread, they became a vector for a variety of viruses. In fact, researchers are finding more and more variants of Deformed Wing Virus (DWV), a virus that affects the honey bee’s essential flight capabilities. Research has shown that DWV-B (Deformed Wing Virus variant B) can be responsible for high over-winter losses.

The point here is that Varroa devastates colonies.  It would also seem that Varroa are transmitting more virulent strains of viruses with each passing year. Because of this, I recommend to keep mite levels below 1 mite/ 100 bees in the spring and below 3 mites/100 bees in the fall. With Varroa loads any higher, beekeepers risk high colony losses.

Monitor, Monitor, Monitor

Beekeepers must consistently monitor mites if they expect to have strong and healthy colonies. Beekeepers can monitor their mites in various ways, but I recommend both of these two methods: perform an alcohol wash (or other monitoring method) and observe the overt signs of mite damage. It is ideal to perform monitoring methods once a month, but we realize this is not always possible. Because of this, combining both monitoring and observation methods are recommended. Ideally, mites should be monitored at least 4 times a year.  As seen in Figure 1: population increase, population peak, population decrease, and fall dormant; it is essential to understand the seasonal changes. For example, brood density varies throughout the year, so certain treatments can be less effective at different times. By understanding seasonal cycles, beekeepers can better manage their mites. I understand Figure 1 does not reflect the reality of every region but it gives a good overall general idea.  Some regions have multiple population peaks due to large honey flows, so you will need to understand the honey bee seasonal phases in your region. But essentially, as the bee and brood population increase, so do the mites.

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Figure 1: Honey bee seasonal phases from the honey bee health coalition- Beekeepers should monitor mites once a month, but this is often not possible. But mites should be monitored at least 4 times a year: late winter-early spring dormant, population increase, population peak, population decrease, and fall dormant. I recommend alcohol washes (or another method) during these periods. Photo courtesy of the Honey Bee Health Coalition

Mite Monitoring Techniques

I attached a chart outlining the 3 major mite monitoring techniques I recommend. Perform one of these techniques 4 times a year: Early spring, late spring, late summer and early fall. Each beekeeper has their preference, so use the method you feel the most comfortable with. I use alcohol washes, but I feel comfortable with sugar rolls or CO2 as well. As long as you monitor, there is not a wrong method!

Advantages  Disadvantages 
Sugar Rolls
  • Known research on accuracy
  • Common method
  • Does not kill bees
  • Messy
  • Hard to do on windy, rainy or humid days
  • More time consuming
Alcohol Wash
  • Known and common method
  • Quicker than sugar rolls
  • Can be more accurate than sugar roll
  • Can be messy
  • Kills bees
CO2
  • Quickest method
  • Easy to do with multiple colonies
  • Kills the bees (most likely)

When monitoring for mites, beekeepers should review mite thresholds. I outline my recommended thresholds for each monitoring method below. If your colony is above threshold, I recommend taking actions. Mite thresholds are not an exact science, even if you have levels below the threshold, it is no assurance that your colonies will be healthy and successful. For example, I have sampled many commercial beekeepers with mite levels <0.5 mites /100 bees in the spring, and they eventually had huge losses. I typically see mite levels spike in the late summer because: A) summer treatment with honey supers are limited, B) Mites are often lurking in the brood, and C) Mites from other beekeepers nearby can (re)infest colonies. Because of this, always monitor and monitor again. Once mite levels do spike, they may be difficult to bring down. Too often, when you notice, the mite damage is already done. I should note that I recommend alcohol washes, powdered sugar rolls or CO2 over a sticky board. Sticky boards are not nearly as accurate, because they do not quantify the level of infestation. If a sticky board is your only option, you can attest that you have some mites or more mites, but you are not able to assess the level of infestation (1, 2, 3 mites/100 bees). Use other monitoring method options for more accurate results and an infestation level to compare with suggested thresholds. *These thresholds may vary per US regions. These are the threshold I recommend in the Midwest (MN & ND)

Monitoring Method # of mites in early-spring # of mites in mid-spring # of mites in late-spring # of mites in early-fall # of mites in late-fall
Alcohol Wash  

1 mite/100 bees

1 mite/100 bees 1 mite/100 bees 3 mite/100 bees 3 mite/100 bees
Powdered sugar roll 1 mite/100 bees 1 mite/100 bees 1 mite/100 bees 3 mite/100 bees 3 mite/100 bees
CO2 1 mite/100 bees 1 mite/100 bees 1 mite/100 bees 3 mite/100 bees 3 mite/100 bees
Sticky Board 9 mites/24 hours 9 mites/24 hours 9 mites/24 hours 12 mites/24 hours 12 mites/24 hours

Mite related Disease Progression 

I inspect and observe hundreds of colonies annually. When I enter a colony, I often immediately know whether it has (or did) have high mite levels simply by observing progressed signs of mite damage. Just observing progressed mite damage does not suffice, but it is a good start. By noting visual signs of Varroa, you will know just how important your mite levels are and the need for action. Monitoring is best but if you can recognize some of the visual signs, you will better understand the extend of the mite damage to your colony.

I outlined the 5 stages of mite damage, which I relay to my beekeepers. In the spring during population increase, I want to see colonies within the Stage 1- 2. While I hate to see mites in the spring, this is not always a bad sign. Even if I observe mites, the colony may be below the recommended threshold, so just continue to monitor that colony. During the late spring, summer and fall, I like to see colonies within Stage 1-3. Even if Chewed Down brood (CDB) (outlined below) and phoretic mites are seen, it does not mean that beekeepers have high levels. However, a combination of phoretic mites and CDB can signal worse mite issues. If these signs are seen, continue to monitor these colonies. As for Stage 4-5, I never want to see these stages, regardless of temporal period. Deformed Wing Virus (DWV) and Varroa Mite Syndrome (formerly Parasitic Mite Syndrome or PMS) can signify high mite levels.  Specifically for Varroa Mite Syndrome, it signifies very progressed mite damage, which often results in colony deterioration and eventual colony death. If colonies are in stage 4 or stage 5, monitor immediately to determine extent of damage. Action is often required, but may be too late.

 Stage Visual Signs Notes
Stage 1 Zero signs of mites, brood diseases or viruses
Stage 2 Visual signs of phoretic mites on either workers or drones.

 

This does not necessarily mean a mite issue exists, but if mites are seen, monitor to determine extent of varroosis.

 

Stage 3 Chewed Down Brood and/or phoretic mites

 

 
Stage 4 Deformed Wing Virus (DWV) and/or Chewed Down Brood and/or signs of phoretic mites. Visual signs of Deformed Wing Virus (DWV) can mean larger varroa issues. Obviously, this depends upon the number of bees with DWV and the number of phoretic mites seen, but mite monitoring is recommended to determined extent of varroosis. These signs signal a more progressed form of varroosis.
Stage 5 Parasitic Mite Syndrome (PMS) and/or Deformed Wing Virus (DWV) and/or Chewed Down Brood and/or Phoretic mites Visual signs of Parasitic Mite Syndrome usually signal extreme issues with varroosis. If Parasistic Mite Syndrome is seen, then mite levels are often a significant issue and has advanced to the most progressed stage of varroosis.

Visual signs

Phoretic Mite

Phoretic mites are Varroa mites seen on the abdomen of worker (or drone bees). Most phoretic mites, however, are found underneath the bee, more precisely tucked between the abdomen’s sclerites where they latch on and feed. Because of this, I typically inspect the ventral abdomen of several worker bees during inspections. This is why beekeepers “never see mites”, even if these beekeepers have higher mite levels. Visually inspect phoretic mites just on the workers, not the drones. If phoretic mites are seen on worker bees, then this represents a more progressed infestation of mites. Signs of phoretic mites indicate the colony is in Stage 2-5. Visually inspect other signs to further pinpoint extent of damage.

 

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Phoretic mite on the thorax of a worker bee. Photo Courtesy of Rob Snyder

Chewed Down Brood (CDB)

Bees can sense mites in the brood. If sensed, bees will uncap and cannibalize the pupae. If CDB is seen, then mites may be at a high level, especially within the brood. CDB can indicate progressed mite damage, so continue to monitor and assess colony health.

Deformed Wing Virus (DWV)

Deformed Wing Virus (DWV) represents the next stage of varroosis progression. Bees with DWV are kicked out of the colony so if bees with DWV are seen than Varroa has become an issue. DWV does not signify un-manageable mite levels for the colony, but it is a more progressed sign of mite damage.

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The bottom right corner contains a cell with chewed brood. Bees begin chewing brood when they sense mites within the cell, so this can indicate larger mite issues. Photo by Rob Snyder

Deformed Wing Virus (DWV)

Deformed Wing Virus represents the next stage of varroosis progression. Bees with Deformed Wing Virus are kicked out of the colony so if bees with DWV are seen than Varroa has become an issue. Deformed Wing Virus does not signify un-manageable mite levels for the colony, but it is a more progressed sign of mite damage.

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This bee has deformed wing virus, a debilitating virus than can easily deplete a colony. Oftentimes, bees with the virus are removed from the colony. So if bees with Deformed Wing Virus are seen, than this can indicate larger issues. Photo by Rob Snyder

Varroa Mite Syndrome (VMS)

A pathogen has not been identified for this diseased, however mites are always present when this disease is seen. This brood symptom looks similar to other brood diseases except the larvae do not rope like foulbrood. Larvae do appear sunken to the side of the cell. If Varroa Mite Syndrome is observed, then colony has likely dwindled and deteriorated. Varroa Mite Syndrome is the most progressed sign of mite damage, and truly at a stage of no return. Even if low phoretic mites are seen, Varroa mite syndrome often means an end to your colony, even if treatment is applied.

Symptoms
  • Spotty brood and Varroa present on adult
  • Mites may be present on brood
  • Mites seen on open brood cells
  • Small population size
  • No odor present, just sunken brood
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Parasitic mite syndrome is the most progressed sign of mite damage. If parasitic mite syndrome is seen, than the damage is done. These colonies will likely collapse, and there is nothing a beekeeper can really do. At this stage, the colony has already dwindled and deteriorated.

Summary

All beekeepers should consistently monitor mites throughout the year. Even if mite levels are low at one point, it does not mean they will stay low. Mite levels can easily spike, so always be aware and monitor and re-monitor. Beekeepers should learn how to monitor and visually inspect for mites. By doing so, varroa mites can effectively be managed. Varroa mites are the most challenging issue beekeepers face, so make sure you know where your colonies stand. If you don’t, then you risk losing your colonies.

Cheers!
Garett Slater