Chemical Synergies: When 1 + 1 Does Not Equal 2
The agricultural environment is a source of chemical exposure for bees, with pesticides, their degradation products, and other ingredients in pesticide products (adjuvants, solvents, and other chemicals added to formulated products) dominating the scene. Because multiple pesticide products are applied to a crop, honey bees foraging on or near the crop will typically bring multiple chemicals back to the hive in pollen, nectar and/or water. In-hive miticides are also part of the picture. Indeed, most analyses of hive materials (pollen, wax, bees, honey) taken from beehives in agricultural areas show that multiple agricultural and miticidal chemicals are present.1, 2, 3
As we think about the potential effects of these chemicals on bee health, it becomes clear that we need to know not only how the individual chemicals affect bees, but also whether the mixture alters the toxicity of individual components. There are three possibilities:
- Additive: Toxicity is simply the sum of the toxicity across the individual components;
- Antagonistic: The mixture is less toxic than the sum of its components would suggest; and
- Synergistic: The mixture is more toxic than the sum of its components would indicate.
In this Curious Beekeeper article, we’ll explore the occurrence of synergistic effects, where 1 + 1 is greater than 2.
It might sound impossible, but there is a firm basis in science for the synergistic effects observed for mixtures of chemicals. It all has to do with how insects (and humans) detoxify chemicals. An analogy is illustrative here.
You’ve seen the cartoon--a bad guy walks into the room and starts to make trouble. But not to fear! The big bouncer guy by the door walks over and picks him up by the scruff of the neck and tosses him bodily out the door. The bad guy gets a black eye and bruises in the process and heads off into the distance. But if the bouncer is on vacation, the bad guy can do whatever he pleases without consequences.
This scenario has much in common with the system used by both humans and insects to detoxify chemicals. In this case, the bad guy is a toxic chemical and the bouncer is a group of enzymes that react with the toxic substances. The chemicals are transformed in the process of interaction with the enzymes, which reduces chemical toxicity and facilitates excretion of the toxic substance. But if the enzyme system is disabled by a synergist, it’s as if the bouncer is on vacation. The toxic chemical is not degraded or excreted, and toxic effects are observed at a much lower dose than without the synergizing chemical.
How Detoxification Works
The most common family of enzymes responsible for detoxifying foreign chemicals in biological systems is the cytochrome P450 group (CYP).4 There are other enzymes involved, but because the CYP group is the primary system for detoxification in insects, we’ll focus on it here.
A set of genes codes for the CYP proteins, and different species and even different individuals have a different mix of CYP variants, with marked variability in the ability to detoxify chemicals. This genetic basis of detoxification accounts for much of the variability in the sensitivity of both humans and insects to chemical substances. It also explains why some people can drink a cup of coffee at midnight and go right to sleep while others have to cut caffeine intake early in the day if they hope to get a wink of sleep.
In insects, CYP enzymes have been studied extensively for their role in the development of resistance to insecticides.5, 6 Insects with CYP enzymes that rapidly degrade an insecticide are resistant to its effects, survive the insecticide treatment, and live to reproduce and pass these resistant genes on to their offspring. In the context of beekeeping, fluvalinate-resistant Varroa mites have genes that produce CYP that is very efficient at detoxifying fluvalinate, so it has little effect on the mites.
Exposure to a chemical may have one of several possible effects on the CYP system. The primary ones are:
- Induction and activation: CYP enzyme activity is enhanced in the presence of the chemical, and the result is a substance that is more toxic than the starting chemical. An example here is the transformation of an organophosphorus insecticide like chlorpyrifos (Dursban®) to its much more toxic oxon form that is then further metabolized and excreted.
- Induction and deactivation: CYP enzyme activity is enhanced in the presence of the chemical and the result is a species that is less toxic than the starting chemical. The adaptation of insects to eating toxic plants is based in their ability to degrade toxic substances in the plant to benign ones.
- Inhibition: CYP enzyme activity is suppressed, allowing toxic chemicals to persist in the ...
Western Apicultural Society (WAS) Meets in Missoula, Montana
Part 1: 2nd International Workshop on Hive and Bee Monitoring
The 37th edition of the Western Apicultural Society of North America (WAS) met at the University of Montana, September 18-20, 2014. With the current President, Dr. Jerry Bromenshenk, at the helm I attended knowing that this would, as the organizers promised, “not be your grandfather’s bee conference.” It did not disappoint. “The Future...brought to you by WAS (and some other good people.)” followed on the heels of Dr. Bromenshenk’s 2nd International Workshop on Hive and Bee Monitoring.
For those not informed about Dr. Bromenshenk, now formally retired as a faculty member at the University of Montana, his employment history is worth examining. He is arguably the only faculty member in the bee research arena at a major university to have supported himself on what is called euphemistically, “soft money.” In short, he has had to earn his living by writing grants, rather than the more usual way faculty members are paid, via a taxpayer-supported salary. In order to do this he has explored some unconventional funding sources, including the Department of Energy, the Defense Department via the Defense Advanced Research Projects Agency (DARPA)1, the US Army USA-CEHR, and the US Army NVESD laboratories. Research funded by these agencies resulted in patented technologies and methods including Smart Hives (electronic hives), laser (lidar) mappingof honey bee distributions, acoustic diagnostics for colony health and chemical detection, and training of honey bees to find land mines. Many of these were on display at the workshop.
Dr. Bromenshenk’s résumé also includes pioneering study using honey bees as environmental sentinels (monitors) via citizen-based science projects and establishing honey bee based protocols of ecological assessments for use by the Environmental Protection Agency (EPA). Finally, he is a major player in Bee Alert Technology2, which is attempting to integrate new technologies into the craft of managing honey bees.
The workshop on hive monitoring brought together a group of highly trained folks interested in finding the keys to looking at honey bee behavior and colony management without physically manipulating the colony. Physical inspection often inserts error into the observations. It featured the activities of a number of different entities, many using a traditional technology, the scale hive, in innovative ways.
Leading off was Jerry Hayes, ex-bee inspector in Florida and now Monsanto Corporation’s Honey Bee Health Lead at the corporation’s newly-formed BioDirect Business Unit. He discussed how scale hives are used in the company’s research on honey bee health in a number of areas. This was followed by Alwyn Smith of Paladin Engineering, also describing using scale hives (so-called “smart hives”) in relation to research by Bayer Corporation’s newly-formed Bee Care Center in North Carolina’s Research Triangle.3
Mr. Smith would be the first of several at the workshop to mention the obvious to attendees: “honey bees are not cows!” It’s relatively easy to do research on cattle, which can be corralled and closely observed throughout their life. Not so for honey bees that forage up to a mile radius from their colony with the majority of their activities hidden from view inside a wooden box.
The list of things that have to be looked at, according to Mr. Smith, include not only what he called “low hanging fruit” (weight, temperature, humidity), but also specialized activity, much more difficult to analyze. These include specific noises (acoustics), thermal outputs of both adults and brood, individual bee trips in and out of the colony (bee counting), and subtle effects of pheromones. Creative measurements of these can answer many of the perennial questions asked by beekeepers over the years according to Mr. Smith: Is the queen alive or dead? Where is the queen? When is the nectar flow? Where do workers go? What do they do? How healthy is a colony in general? Based on what parameters?
From my perspective, a star of the show at the workshop had to be the current monitoring efforts of an outfit calling itself “Arnia.” Arnia is the Italian word for beehive. This company was formed by Dr. Huw Evans and his wife with specific objectives as noted on the web site.4
The Arnia system sports a delightful user interface and marks the first commercially available, complete system to be marketed at relatively low cost to small-scale and backyard beekeepers. It is a complete system with a basic set of sensors (e.g., hive weight, temperature, relative humidity, bee sound) and cellular communications. It seeks to help answer numerous questions beekeepers might have. How many beekeepers, for example, would like to receive a text message notifying them that their supers are full, or a colony has gone queenless, needs winter feed, was knocked down or blown over, perhaps stolen?
Arnia’s monitoring efforts began by looking at acoustics for swarm control, but now include scale hives5, as well as information on brood nest temperature, and humidity. Arnia distinguishes itself over simpler hive-scale systems by collecting a huge amount of data remotely, in real time on a routine basis. This information reveals the “wisdom of the crowd,”6 which appears to mirror how humans, honey bees, and many other biological phenomena self-govern. The activity also fits with the idea of collecting what is being called “big data.”7
Arnia appeared to be the “gold standard” at the moment, as featured at the Missoula workshop, having the most advanced, commercially-available, single-hive system on display. However, others are currently in the pipeline and capacity is rapidly building. Initiatives not prominently featured at the event include those by commercial beekeeping supply outlets like Swienty and Mann Lake Supply, as well as Bee Alert Technology. The latter is targeting large-scale applications for beekeepers in the U.S.
An example of the use of the Arnia system was provided by Robert McCreery of the Dromore Beekeepers Association in Northern Ireland.8 This activity (Journeyman Hive Monitoring) is considered a cornerstone of “Strategy for the Sustainabiity of the Honey Bee,” a program of Ireland’s Department of Agriculture and Rural Development9, which was initiated in 2011.10
Other activities mentioned by Mr. McCreery include a distributed pollinator study, categorizing pollen diversity and analyzing flowering times (phenology). Of utmost importance is its use in schools and educational institutions, as well as in the field of what is being called “citizen science,”11 where beekeepers themselves become an integral part of a research team.
Citizen Science Project
Citizen science was pioneered by Dr. Bromenshenk in his early studies using bees as environmental monitors of air quality in the Pacific Northwest. Dr. Wayne Esaias, recently retired from NASA’s Goddard Space Center discussed the origins of his citizen science project, which began in 2006, when he farmed out some hive scales to beekeepers around the U.S. Now called HoneyBeeNet12, this is reaching a network of beekeepers, that continues to actively gather data. The genesis of this initiative is spelled out in a NASA blog post13:
“Esaias, who works at NASA’s Goddard Space Flight Center in Maryland, has been studying this cycle of beehive yo dieting in the U.S., as he explains in the video above. By combining hive weight changes with space satellite data that reveal vegetation change on the ground, along with other data that go back to the 1920s, he has found that the timing of spring nectar flows has undergone extraordinary change. ‘Each year, the nectar flow comes about a half-day earlier on average,’ says Esaias. ‘In total, since the 1970s, it has moved forward by about month in Maryland.’ In an interesting demonstration of citizen science, Esaias has set up a network of amateur beekeepers —HoneyBeeNet— who use industrial-sized scales to weigh their hives each day.”
Since its beginnings, Dr. Esaias reported at the workshop, the HoneyBeeNet project has made great progress in analyzing what’s going on outside the hive. Important areas of interest include indirect climate impacts on plants providing nectar. He emphasized that “honey bee nectar flow” is what is being looked at, and not necessarily correlated with what many beekeepers call the “honey flow.”
Warming of the climate continues to be the focus of Dr. Esaias’ efforts, which have delivered some intriguing conclusions. The role of “invasive” species is now being looked at from different perspectives. Could these plants be a godsend if native species can’t survive in the region they are originally adapted to? A comparison of trees as major nectar plants in the northeast vs plants in other areas brings into focus regional differences in bee forage that must be taken into consideration when making honey bee management decisions.
Unfortunately, with the retirement of Dr. Esaias, the future of HoneyBeeNet is in doubt. It appears that at least some of this effort will be taken up by the University of Maryland’s sentinel hive project,14 which is using crowd funding. Potential citizen scientists are being asked to raise money to fund a pilot program of 10 Sentinel Hives with pollen and disease monitoring. Money raised will fund extra Sentinel Hives. This initiative is due to end in October, 2014, but if successful should continue the program.15
Another hive monitoring approach mentioned at the workshop that is currently in use is Hive Tracks. According to its web site,16 “Hive Tracks is a powerful computer application accessed through any Internet Browser. It can be used from a laptop, desktop, iPad, iPhone or other type of smart phone with Internet access.” The approach is similar to that of HoneyBeeNet in that bee and hive data is periodically collected in the bee yard and can be transferred via the Internet. Both Hive Tracks and HoneyBeeNet differ from Arnia in a crucial way; neither is real time, remote monitoring, relying instead on a beekeeper physically visiting the bee yard and collecting data from individual colonies.
The relative costs of the approaches discussed above are quite ...