What is your varrroa control plan?

It has become obvious that we cannot reduce the stress that varroa mites cause to our honey bee colonies by starting our mite control in the fall. Although it is the dispersal (phoretic) mites feeding on colony adults or reproducing mites in capped pupae cells that we control, the real issue is that mites enable the spread of the deformed wing and paralysis viruses that lead to colony death.

Most of you have had a chance to look at bees this spring. We MUST flatten the mite growth curve NOW as our bee colonies and the mite numbers start their spring expansion. Virtually all colonies are now rearing drones; some have started queen cells. There will be swarms from some colonies. Busy time for colony expansion – and for the mites to expand too.

I have had great response, as per usual, from WVBA members with the PNW annual survey I have been doing each spring. So far as of April 1, 19 WVBA individuals (down from 24 last year) have filled out a survey form. One hundred twenty-four fall colonies were reported but unfortunately 11 were dead. That represents a loss rate of 9% as I indicted at the March 23 monthly meeting. Average previous 10-year loss rate for WVBA is 30%; last year the loss rate was 25%.

If you have not returned a survey, it is still open until April 30^th. Thank you to WVBA for the great response to the survey this year.

While loss of 1 of 10 colonies is better than average, it is still too high. Purchase of a nuc or capture of a swarm can repopulate the empty equipment. However, it still is a loss. If you have experienced losses higher than the average, I recommend you look at your plan for annual mite control. A proactive plan should start NOW! Waiting until fall to control mites is too damaging. Control begins NOW.

Removing drone brood should be in your plan. In the spring expansion, foundress mites select drone cells for reproduction. They can grow their population more rapidly as the two extra capped days of drone pupal development allow female foundress mites to produce 3 female offspring on average. In a worker cell, only one new female is produced.

Mites do not select drone cells at random, but we do not know exactly how a foundress female mite decides which drone cells to invade. Eliminating drones before they emerge (=Drone Brood Removal) will significantly limit the mite population growth as evidenced in several research studies. Female mites only have 3-5 brood rearing opportunities in their lifespan, so removing a capped drone cell significantly limits growth of the mite population.

Using an organic acid (formic) or essential oil (Apiguard or ApiLifeVar) will also reduce the female mites dispersing on adult bees before they can enter a brood cell to reproduce. To keep mite numbers low, oxalic acid on extender pads (Varrroxsan) interferes with mite dispersal and limits reproductive success ensuring their growth rate is reduced. All these techniques, with exception of double strip Formic acid in one treatment, cause minimal harm to the expanding bee population. Formic acid of one strip, followed by a second strip, is less likely to cause harm but it is also less effective against mites in capped cells.

I have begun a Beekeeping Today Short Podcast series Bee Science with Dr Dewey Caron. The 3^rd Wednesday segment of April – 4^th of the series - has further details and literature to examine on effective spring mite control. The 3^rd podcast discusses the essence of a proactive IPPM (Integrated Pest & Pollinator Management) mite control plan.