Varroa

There are a lot of theories as to the cause of Colony Collapse Disorder (CCD). Is it pesticides, over medication, increased stress from transporting bees, mites, all of the above or something else? There isn't a definitive answer but we do know each spell trouble for Apis mellifera or the honey bee. This is why I choose to raise my bees as holistically as possible and why I chose to end the use of chemicals on my yard 5 years ago. My lawn is still nice and green, it just has more clover and crabgrass mixed in.

Of all of the possibilities for CCD, the one topic that seems to get the most airplay is the Varroa destructor mite (pic 1, red dot on back of bee). Introduced in 1987, this mite has essentially wiped out 98% of the feral or wild honey bee population across the US and has the largest econimic impact on the beekeeping industry of any parasite. Known as an external parasite, V. destructor can only breed in a honey bee colony. The female mite lays eggs in drone or worker brood which attach to the larva and emerge with the bee when it hatches. The mite sucks the hemolymph of the bee resulting in Deformed Wing Disease, weakens the bee and can finally kill it.

There are chemical, mechanical and biological treatments to keep the mite population in check. I'd like to discuss what I am doing to try to minimize Varroa in my hives.

I've mentioned numerous times in the blog that I "sugar" the bees (pic 2). This is the practice of dusting the bees with confectionary sugar. The theory is it causes the mite to loose its grip on the bee and fall off. Since I use a screened bottom board (the board the hive rests on has a large screen mesh for its center), the mite falls out of the hive onto the ground. Unless the mite can attach itself to another bee, it will remain there and die.

Hive 2 uses a "small cell" plastic frame made by Mann Lake. The diameter of the cell imprinted on the frame is 4.9mm as compared to most frames which are 5.4mm. When bees are allowed to make whatever size comb they want they usually make a smaller size 4.6 - 5.2mm cell. Michael Bush calls this "Natural Cell Size". Years ago, foundation manufacturers thought it would be a good idea to make larger honey bees so they would make more honey. By increasing the cell size the egg is laid in, they reasoned a larger bee would result–which it did. Now introduce Varroa which only replicates in honey bee cells. Larger cells means more room for more mites. More mites, more problems. Regress the bees to their natural cell size and you limit the amount of mites that can grow in the cell. The truth be told, this hive has had problems all season and I wonder if it is the cell size. Package bees and queens are not raised on small cell and it takes them quite a while to regress to that size.

Which brings us to drone frames (pic 3). Drone cells are naturally larger, up to 6.4mm, as the drone bees are larger than workers. V.destructor prefers to lay her eggs in drone cells because there is so much room. Today you can buy drone frames which are green plastic for easy identification. The are imprinted with a 6.4mm cell size and after the bees draw out the comb, the queen lays mainly drones in the cells. Now you have a frame of bees that you really don't need that the mites will love. Once you find capped drone cells on the frame you have 21 days (incubation time of a drone bee) to remove the frame and freeze it, thereby killing the drones and the mites before they hatch. You need 2 drone frames per hive to rotate frames between freezer and hive. Picture 4 shows three V.destructor mites that were on larvae when I froze this frame. I opened about 40-50 cells this evening and found 5 mites. I'm going to do a roll test soon to determne the mite population in the hives–but more on that later. Suffice it to say there are holistic ways to control this predator and I plan to try all of them before I use chemical intervention in my hives.