|Varroa Mite on a queen bee|
|Worldwide spread of the Varroa Mite|
While there are many proposed forms of bio control of Varroa (i.e. Metarhizium anisopliae, Beauveria bassiana ...) the predatory mites used to control Varroa are a species of Stratiolaelaps mites (Hypoaspis) which have been used for biological control in horticulture for over 15 years (Stratiolaelaps). This predator mite attacks the phoretic (adult) stages of the Varroa mite. The idea is that they can keep the Varroa population at a low level which does not significantly effect the colony. Unlike some chemicals Stratiolaelaps (Stratiolaelaps) can be used throughout the year (during the nectar season), there is no accumulation in the hive wax and presumably no adaptation by the Varroa.
The results from the early stages of testing of the use of Stratiolaelaps have been mixed. The "Niagara Beeway" in southern Ontario have reported positive results.
Varroa Mite Final from Electric Dreams Video on Vimeo.
As part of the Bee Informed survey Brookfield Farm in northwest Washington State found Strateolaelaps did not reduce the population of Varroa in the bee colonies. Here is a great post by Brookfield Farm detailing the methods and results of predatory mite usage (Mites that might eat mites). The issues regarding the use of Strateolaelaps are that they only works on adult bees (not the larvae where mite reproduction take place), do not work on heavily infested hives, are expensive and they leave the hive for their natural environment in the soil.
Phil Chandler, the "Barefoot Beekeeper" proposes the use of an "Eco Floor" in a Top Bar Hive in this case to provide a natural environment for predatory mites. The Eco Floor can be adapted to any style of hive.
"A simple modification to the floor of the horizontal (Kenyan-style) top bar hive improves insulation, reduces air exchange at floor level and creates an enclosed ecosystem designed to provide habitat for earwigs, wood lice, moulds, fungi and myriad other flora and fauna that may be found inside the average hollow log - the natural habitat of the honeybee."
"No creature on Earth lives in isolation from all others. All sorts of relationships develop between different species, many of them mutually beneficial. Yet honeybees are usually housed in sterile, wooden boxes with little opportunity to come into contact with the myriad other bugs, beetles and bacteria found in their natural habitat: hollow trees. Little is known about the effects on bees of other organisms, but it seems reasonable to suppose that because they have co-evolved with a whole range of other species over tens of millions of years, they will have developed mutually beneficial relationships with some of them." Phil Chandler
In this video Phil Chandler shows how the deep floor is made and how it can be retro-fitted to any top bar hive.
As of yet Phil has not done any studies on long term resident population of Strateolaelaps in the hive (Eco Floor). The problems with the "Eco Floor" are the hive is generally warmer than the natural environment of Strateolaelaps (soil), there is no light in the hive to allow for plant growth (part of Strateolaelaps diet) and there is no evidence that Strateolaelaps will leave the soil and travel upwards through the frames to feed on Varroa.
In New Zealand there are preliminary studies being carried out on the use of Pseudoscorpions as predators of Varroa (Pseudoscorpion Study). There are also preliminry studies from the University of Warwick (England) (Varroa killing Fungi) on naturally occurring fungi that kill the varroa mite. They have narrowed the field down to four potential lethal fungi and are determining the method of delivery (i.e. foot bath, spray..). In addition mycological researcher Paul Stamets has found that mushrooms offer many benefits to bees including detoxification, immunity booster and disease control, and increased longevity of worker bees.
|These graphs show the effects of mycelium fungi increasing bee survival rate and longevity|
In Germany they are studying the use of mite sex pheremone to disrupt male sex activity and have found a significant reduction in mite reproduction.
For many years researchers have been studying the effects of heat on Varroa. At temperatures above 39 celsius (102 fahrenheit) mites suffer irreparable damage while bees can manage temeratures up to 45 celsius (113 fahrenheit).
There have been many marketed hive heaters from the inexpensive Mite Zapper , to the under hive mounted Hive Sauna to the Thermosolar Hive above ($650 U.S. plus shipping). To enable exacting heat control so as not to harm the bees expensive sophistication appears paramount. There is also the issue of honey deterioration at high temperatures. Heating honey to 37 celsius (98 fahrenheit) reduces nutritional value.
On a unrelated note a BYU undergraduate is working on a biocontrol of American Foulbrood. Phages (microscopic bugs) are used to kill the AFB bacteria.
“Phages are the most abundant life form on the planet and each phage has a unique bacteria that it will attack,” said Sandra Burnett, BYU professor of microbiology and molecular biology. “This makes phage an ideal treatment for bacterial disease because it can target specific bacteria while leaving all other cells alone.”
The trick is identifying the right phage. They have narrowed it down to 5 phages (Research article).
I believe the future of dealing with Varroa will be breeding for Varroa Sensitive Hygienic (VSH) behavior. Many including myself believe that the VSH behavior traits are passed both genetically and through observed learning. In hives with VSH behavior bees, bee pupae infected with mites are detected and removed. Other VSH behavior traits include: more effective self grooming; group grooming; guard bees removing mites from bees entering the hive (either killing the mites or chasing them from the hive) and bees using their mandibles to kill the mites. Decreased drone production (most mite reproduction takes place in drone brood) and a higher resistance to diseases (the diseases passed by the mites kill the bees not the mites themselves) are also desirable breeding traits. While there are very positive results of breeding queens for VSH behavior the long term problem is the inability to flood the area breeding population (drones as well) with bees possessing VSH traits. It is important to remember that Asian honey bees (Apis cerana), African honey bees (Apis mellifera scutellata), Africanized honey bees (hybrid European and African) and a strain of Russian honey bees display VSH behavior and are effectively resistant to the varroa mite. Some believe that the unnaturally increased size of Apis Mellifera (carried out 100 years ago to increase honey production) hinders their attempts to remove the mites and the enlarged areas between body segments allows for mite penetration. If true this would support the beliefs of natural, small-cell beekeepers who also support the practice of non treatment. To this point there is no scientific, conclusive proof of this theory (some natural beekeepers would argue this). The video below shows bees displaying VSH behavior by removing mites (removal at the 2 minute point of the video).
For further information on hygienic behavior in honey bees go to the Hygienic Behavior section of our Beekeepers' Library.
While I don't profess to know the perfect solution this year I used Mite Away Quick Strips (naturally occurring formic acid) to control the varroa population. I also advocate the splitting of colonies which serves to deter swarming and provides a month long bee brood break which creates a Varroa brood break as well. I hope that whatever method of mite defence you employ is successful and that you and your bees are healthy and happy.
"There is no other field of animal husbandry like beekeeping. It has the appeal to the scientist, the nature lover, and even (or especially) the philosopher. It is a chance to work with some of the most fascinating of God's creatures, to spend time and do work in the great outdoors, to challenge my abilities and continue to learn. My hope is that I never become so frail with old age that I cannot spend my days among the bees. It gives credence to the old saw that "the best things in life are free". I thank God daily for the opportunity and privilege to be a beekeeper."