IPM 5 Fighting Varroa : Biotechnical Tactics – Part 1

IPM 5 Fighting Varroa :

Biotechnical Tactics 1

Randy Oliver

ScientificBeekeeping.com

First Published in ABJ in April 2007

(Fifth in a series on Integrated Pest Management of Varroa)

(Photos to be added – check back)

In the “silver bullet” model, any mite kill less than 95% was considered ineffective. Unfortunately, the days of that kill rate are fading for most synthetic chemicals. It would be wise for beekeepers to consider an alternate model of mite management. In the IPM model, incremental mite kills of even a few percentage points are adequate, if begun early in the season, and continued or repeated.

Introduction

Let’s talk about separating fact from fancy. When reviewing and summarizing research, it is easy to pick and choose to support one’s own opinion or what one “believes in.” We expect the promoters of a product or persuasion to do so, and take their “data” with a grain of salt. Even objective scientists are not immune from interpreting data to support their pet hypotheses. The reader has every reason to wonder if I’m doing the same. Let me state that I have no preconceived notion of the best way to win the battle against varroa. I approach each research result with an open mind. I question and pick apart scientists’ conclusions, call or write the authors for clarification, and sometimes replicate their experiments in my bee yard. I find appropriate gems of important information in obscure journals (read the reference lists at the ends of my articles). Eventually, a sort of “big picture” comes into focus. If I find research that appears contrary, I promise the reader that I will report it, too. I certainly don’t have it all figured out, but I do see that there is a great deal of research out there that is applicable as to how we can successfully manage the mite.

Miticide rotation is indeed working currently to control varroa, but its days are likely limited as the prime method of keeping the mite in check. Putting all your eggs in one basket, i.e., depending 100% on some chemical to miraculously stave off the mite for yet another year, is a risky strategy, especially if you don’t have a Plan B. (For what it’s worth, when I review chemical miticides later in this series, I am not going to give a blanket recommendation against them. I am rather going to present a rational analysis of how each one might best fit into an IPM strategy, should one wish to use them.) The wise operator will open his/her eyes and mind to alternative approaches, and familiarize themselves with new strategies, so that if the miticides fail, you won’t be caught flatfooted. However, I totally understand peoples’ natural resistance to tread in unfamiliar territory, and the “if it ain’t broke, don’t fix it” philosophy. Delaplane and Ellis (2006) hit the nail on the head by stating “No matter how well IPM controls Varroa, beekeepers will not adopt it until it has been shown to be advantageous practically and economically.” In their study, involving six collaborating beekeepers, those colonies managed with IPM produced more honey, had about the same level of mites, and experienced fewer queen losses and colony deaths than the colonies treated with Coumaphos. Most telling, though, was that the IPM colonies required less beekeeper labor than either Coumaphos-treated or control colonies!

Here’s the point to note when comparing IPM practices to the “silver bullet”: Mite- and chemically-induced queenlessness, colony loss and subsequent restocking, poor colony buildup and production, and susceptibility to other diseases all cost in you extra labor, greater out of pocket expenses, and lost potential income. Effective IPM practices can actually save you labor overall, and put more profit into your pocket! I know that that statement sounds like a helluva sales pitch, but I’ve got nothing to sell. I could easily use this bully pulpit to sell snake oil or gadgets, but in order to maintain my integrity, I’m purposely avoiding that at this time.

I suggest that you run some trials in a few yards, and see how alternative methods work. A word of caution: try new methods on a small scale first! I’ve been working out techniques to make alternative methods cost effective for commercial operators, and I’ll share what I’ve learned with you. Please note: I’m still very much on the learning curve, and fall on my face from time to time. I solicit feedback on what works for you, and what doesn’t. I’ve put innumerable hours into researching what has worked in controlled trials by researchers worldwide, plus what has worked or failed in the field for other beekeepers, and I test most everything in my own operation. I’m still low on the learning curve. But I’m learning!

Commercial operators may wish to remember that they are not unique. Beekeepers in other countries have been using exactly the same ag chemicals as they are, and for a longer time. Their experiences provide us with a “heads up” for the future. We can see where the train is heading, and it ain’t down the synthetic chemical track. Not because of idealistic notions, but for the very practical reason that after a few years of use of a new miticide, the mites just laugh at it! We may only have a few years before the train wreck occurs when mites develop resistance to all the “easy” chemicals. Personally, I’m getting off the train that appears to be going toward a dead end, and getting on the train that tackles the mite head on, and wins. Hop on with me if you wish.

In my previous two articles, I’ve detailed varroa population dynamics and techniques for monitoring mite population levels. As you’ve seen, varroa is far from invincible—in fact, even a small whittling away at its reproductive rate, or a slight added increase in its mortality rate can keep it from reaching critical levels in a season. Think of it as a “war of attrition,” rather than a battle. In the “old” model, we simply blasted the mite with chemicals from time to time. In the IPM model, we hit the mite from all angles at all times, and use chemicals only as a last resort. In this article and the next, I’ll discuss several techniques that can be used to put the hurt to the mite. “The descriptive term ‘biotechnical’ refers to practices in which the beekeeper manipulates the environment of the hive, or conditions within the hive, such that the biology of the mite works against itself” (Hoopingarner 2001).

Some biotechnical techniques may hamper the mite only slightly; others are extremely effective. I will begin with minor tactics, such as general apiary management, then go on to comb considerations, queen and brood manipulation, screened bottom boards, and in the next article in the series, the potentially effective “one-two punch” combination of using drone brood trap combs and powdered sugar dusting. I’m not going to waste your time detailing methods that appear to me to be impractical or not cost effective.

Apiary management

Here are a bunch of quickies. Most are common sense. Are you practicing them?

Avoid shade and keep colonies warm and dry. There are several reports of colonies faring better against mites when kept out in the open. Rosenkranz (1988) found that varroa prefer relatively cool temperatures of 75-88°F, well below the central brood nest temperature of 95°F. Harris, et al. (2003) state that “research by others has shown that high temperatures and extremes in relative humidity within the broodnest of a colony of bees will reduce the number of varroa mites that lay eggs.”

Keep yards isolated. Avoid picking up your fellow beekeeper’s mites and diseases. This may be difficult to achieve for the commercial operator, but it can really hold down reinfestation due to robbing.

Educate your neighbors on varroa management. If your neighbor is losing colonies to the mite, you will too! Pettis and Shimanuki (1999) documented mite immigration of up to 136 mites per colony over a 3-day period in September. This kind of reinfestation can thwart your best efforts at mite management.

Watch for failing colonies before they collapse, so they don’t get robbed out. Minimize collapsing colonies, deadouts, and robbing–all these spread mites (and other diseases). Create a quarantine yard. Don’t let the occasional sick colony become an epidemic in your operation. Kill or isolate collapsing colonies so that especially virulent mites and viruses don’t spread.

Don’t combine collapsing colonies–you may be contributing to the spread of virulent mites or viruses. Beekeepers learned this lesson the hard way this year with Colony Collapse Disorder.

Swarming

If we were to let Nature play her hand freely, mite-susceptible lines of bees would rarely get strong enough to swarm, and their drones would be hampered in their ability to mate. Therefore, the genes for nonresistant bees would not be passed on to subsequent generations. However, when we rescue these colonies with chemical treatments, we thwart Mother Nature in her ruthless selection process, and thereby perpetuate nonresistant bees in the feral population. Those danged swarms will then come back to haunt us when they eventually collapse, and our managed bees gleefully bring the mites back in the process of plundering the deadouts.

The main mode of mite immigration into colonies appears to be from the robbing out of collapsing colonies, as opposed to by drifting or absconding bees (Goodwin, et at. 2006). As long as we keep restocking the feral colonies with nonresistant swarms, we just create a huge reservoir of mites that will screw up our best efforts at varroa management. Natural swarms produce far more drone combs than managed colonies on foundation. Varroa reproduction is therefore far greater, leading to the relatively rapid collapse of swarms.

So, what to do? If you’ve got good mite tolerant stock, let ‘em swarm. If not, minimize swarming to the best of your ability. You may even wish to try pheromone-baited swarm traps. I did. Last spring I purchased a bunch of swarm lures. The day they arrived, we saw a swarm taking off. So I handed a lure to a willing apprentice, and had him hold it up in the air. Danged if that swarm didn’t just come right down and cluster on his hand! Obviously, we had the surefire way to attract swarms! So I built a dozen swarm boxes from deep supers with hive flats screwed on top and bottom, a 1” hole for an entrance, and a citral/geraniol lure. I hung the traps around my beeyards, carefully placing them in trees where swarms had previously landed. During swarming season we kept careful records of the number of swarms that tenanted our deluxe scented domiciles. Results: swarms captured—zero. However, it’s been reported that swarm traps work great in some areas. I suggest you try a few before you make a big investment.

Bottom line: keep colonies warm and dry, isolate sick ones, and minimize swarming.