(graph from Dr. Marion Ellis)
The following is based on various research and years of observing mites decimate untreated colonies. I do not claim to have all the answers nor do I wish to give the impression that my recommended methods are absolute doctrine. I only wish to share experience with the bee keeping community in order to show that there are ways to combat this parasite without the use of poisons within the hive.
Understanding the Basics
Making simple assumptions for this scenario, assume the colony went into the winter healthy OR we have a new package, first season colony. At this point, the colony is assumed to be healthy! This colony is not treated with anything.
The colony population is a cycle of rises and declines in both Bee and mite. Starting in spring; the time of year when the colony is building up its work force, the queen begins to lay eggs in the core brood nest as cells are emptied of honey and become available. At this time worker bees are preparing these cells for the queen to lay in which includes cleansing debris and any lingering pests! The mite population for a healthy colony is in check at this point. Looking at the graph you can see the bees maintain a relatively higher population than the mites. This is the host parasite ratio the colony CAN exist with, provided there are no additional stressors placed on it. A stressor can be anything from pesticide problems to bee keepers that need to play with their bees every chance they get!
In this scenario after mid April the converging lines show what can happen if an additional stressor is placed on the colony. This can happen anywhere along the time line! Proceeding along the time line the two populations are beginning to close in on each other, this is where the danger begins.
A probable cause is the bees change in focus to preparing for the winter. Part of their preparation is a reduction in colony population to optimize their use of winter stores. The mite population is still increasing No longer are they picky about drone cells now, it’s a matter of survival, so any cell will do for mite reproduction. Where the two lines cross marks the economic threshold (the point at which the host can no longer support itself and the parasite.) After this point has been reached, you will see bees emerge from the colony with deformed wings (DWV) deformed wing virus and a host of other nasty viruses known as PMS (parasitic mite syndrome) as the mites parasitize what little brood is left. As long as there is brood this will continue and eventually result in the failure of the colony.
Identifying the Change of Focus
A decrease in bee population in a colony occurs naturally on two occasions, the first being reproductive swarming and the latter being preparation for winter. This change in focus is marked by a decrease in laying by the queen and the back filling of the brood nest with nectar/honey. When we treat a hive we knock down the mite population and keep the two lines from crossing thus maintaining the host parasite ratio the colony can sustain!
Our aim is to create conditions in which our bees can attain a state of sustainable, dynamic balance with the mites and other invaders that will always be present in and around a colony. One way in which we can help them is to reduce the mite load at critical points using a treatment that has significant impact on the mites and minimal impact on the bees.
There are several treatment options that do not require the use of synthetic miticides, such as organic acids, sugar dusting and 'shook swarm'. While organic acids (such as formic, lactic, acetic and oxalic) are widely regarded as effective and 'natural' compared with synthetics (such as pyrethroids and organo-phosphates) they nevertheless pose a health risk for the beekeeper and are not entirely benign towards the bees. Sugar dusting is, we believe, entirely harmless for the bees and has a significant knock-down effect on mites, caused by interference with their ability to cling to their hosts. The bees clean the powdered sugar from each other and thus may physically assist in the mite drop.
Shook swarm has been practiced for many years by beekeepers as a control for European Foul Brood. Done at the right time - in spring, as the colony is building up strongly and may be making swarm preparations - it can be an effective way to both radically reduce the mite load and to propel the bees into 'new swarm' mode, when they will work with renewed vigor as if they had, in fact, swarmed. Nevertheless, there are risks with this procedure and if the timing is wrong, the bees may abscond or fail to thrive.
Overall, it is important to remember that we, as beekeepers, can be the primary cause of stress to the bees in our care and that it is an important part of good husbandry to strike the right balance between correct monitoring and too much interference. The bees know what they are doing: our job is mostly to keep out of the way.
What to Look For
The signal that it is time to do something is an increase in natural mite fall. This signals a stressor that the colony encountered and cannot handle at this point. A smart chemical free beekeeper should break out the powdered sugar and dust each frame, repeating two weeks later to ensure you get as much of the mite cycle you can! Should you have a bar of capped drone brood you can pull it out, freeze it, and return it to the colony to be cleaned.
Why is the TBH hive conducive to bee sustainability?
A proven contributor to the survival of the colony is natural comb. Natural comb allows the free building of comb by bees at the bees will. This in turn allows the construction of “the core brood nest” this is the part of the nest constructed with smaller cells. It is the part of the nest that is reserved and cleaned for periods of reduced brood rearing. This is why “small cell’ worked so well. The theory of small cell (first mentioned by the Lusbys) was just never thought through to the end until Dennis Murrell came along and finished it. We have Dennis to thank for all the references to the core brood nest contained here in. The cleaning of this part of the brood nest keeps the mite load in check at crucial times of colony development.
Anything extraneous added by the beekeeper i.e. foundation, frames and artificial feed can be grouped into the category of stressors. So use a Varroa screen w/sticky board to monitor mites and remember it was never intended to be a ventilation device!
Anything you do that decreases the mite population keeps the two lines on the graph from crossing which translates to maintaining a higher bee population. Using sugar dusting and drone comb trapping methods are the “softest” non chemical approaches available today. The most efficient times to treat are the periods just before the mite population reaches the bee population or “the economic threshold” A colony just beyond this point can be saved, however, the chances for survival decrease every day left untreated there after.
A few of many references:-