Carbon Dioxide Gas Combats Bed Bugs

July 24, 2012

CARBON DIOXIDE GAS, an essential nutrient for photosynthesis and the human and animal food chain consuming green plants, can also play a key role in bed bug control. As an attractant, carbon dioxide (CO2) is useful for monitoring and trapping bed bugs and other vampire-like blood-suckers attracted to the gas, including ticks, mosquitoes, and assorted biting flies. Carbon dioxide gas, which has been used to fumigate everything from stored grain and food products to freight containers, museum collections, and hotel and motel rooms, can also be used to fumigate clothing, furnishings, books, electronics, and other bed bug-infested items.

Carbon, carbon dioxide, and the carbon cycle are integral to our very existence on planet Earth. “The carbon of the Earth comes in several forms,” writes University of Cambridge chemist John Emsley in his fascinating Oxford University Press book, Nature’s Building Blocks (An A-Z Guide to the Elements). “Most of what we eat –carbohydrates, fats, proteins and fibre – is made up of compounds of carbon…most ingested carbon compounds are oxidized to release the energy they contain, and then we breathe out the carbon as carbon dioxide. This joins the other carbon dioxide in the atmosphere, from where it will again be extracted by plants and become part of the carbon cycle of nature…The cycle rules the tempo of life on Earth and turns over 200 billion tonnes of carbon each year…In this way carbon is passed up the various food chains, with each recipient releasing some as carbon dioxide, until most carbon is back where it started.”

Does this mean that using carbon dioxide for bed bug control is environmentally acceptable, since it is kind of a “miracle of life” gas behind photosynthesis and plant life? Or is carbon dioxide really more the evil greenhouse or global-warming gas causing global climatic havoc and deserving of punishment via carbon taxes and elimination from the atmosphere via geological carbon sequestration (storage) schemes? Perhaps we should offset carbon dioxide releases for bed bug pest control with offsetting carbon dioxide injections into greenhouses, where elevated CO2 levels increase yields of greenhouse roses, tomatoes, cucumbers, peppers and other crops.

“Carbon is probably the most important element from an environmental point of view,” writes Emsley in Nature’s Building Blocks. “The Earth’s early atmosphere may have contained a lot of carbon dioxide and methane, but once life evolved that began to change. Today, there is very little of these gases and a lot of oxygen instead, thanks chiefly to the action of plants which convert carbon dioxide and water into carbohydrate and oxygen by photosynthesis. The Earth’s atmosphere contains an ever-increasing concentration of carbon dioxide and carbon monoxide, from fossil fuel burning, and of methane, from paddy fields and cows. Human contributions to these sources are still minor compared with natural sources: most carbon dioxide comes from plants, microbes and animals, while methane is given off by swamps, marshes and termite mounds.”

Obviously best to avoid bed bug infestations, and not have to think about remedies like carbon dioxide trapping or fumigations. Italian chemist Primo Levi makes the most persuasive literary argument: “Carbon dioxide, that is, the aerial form of carbon…this gas which constitutes the raw material of life, the permanent store upon which all that grows draws, and the ultimate destiny of all flesh, is not one of the principal components of air but rather a ridiculous remnant, an ‘impurity,’ thirty times less abundant than argon, which nobody even notices. The air contains 0.03 percent; if Italy was air, the only Italians fit to build life would be, for example, the 15,000 inhabitants of Milazzo in the province of Messina. This, on the human scale, is ironic acrobatics, a juggler’s trick, an incomprehensible display of omnipotence-arrogance, since from this ever renewed impurity of the air we come, we animals and we plants, and we the human species, with our four billion discordant opinions, our millenniums of history…”

Bed bugs concern themselves little with environmental correctness, and just tune into characteristics like the heat and carbon dioxide released by metabolizing warm-blooded meal hosts like humans, poultry, rodents, rabbits, etc. A flush from a CO2 cartridge is enough to flush bed bugs from their harborages or hiding places onto a bed in search of a meal. But more naturally, bed bugs follow CO2 gradients to locate live hosts for their blood meals.

“Carbon dioxide has been shown by several researchers to be the most effective attractant for bed bugs,” University of Florida-Gainesville entomologist Philip Koehler told a recent Entomological Society of America (ESA) annual meeting. Humans produce about 700 mg (0.02 oz) of CO2 per minute. “Thus, detectors with very slow CO2 releases cannot compete with human hosts,” said Koehler. “A rapid CO2 release is a better mimic to the human breathing pattern. Detectors with fast CO2 release captured about 4x more bed bugs than detectors with slow release.”

Trapping or monitoring bed bugs with CO2 is complicated by the fact that at different times in the life cycle bed bugs seek out hosts (releasing CO2) for blood meals when hungry; and then when well-fed, instead of CO2 bed bugs seek shelter in groups or cracks and crevices. So although CO2 is the better lure for hungry bed bugs, bed bugs that have fed have different needs and respond to different lures.

A commercial product, FMC’s Verifi(TM) trap, is a dual-action detector combining “fast CO2 generation with liquid kairomone and pheromone lures to attract both host-seeking bed bugs and aggregation-seeking bed bugs,” Koehler told the ESA. Carbon dioxide and the kairomone lure blood-seeking bed bugs into a pitfall part of the trap from which there is no escape. A pheromone lures harborage- or aggregation-seeking bed bugs seeking shelter in cracks and crevices into another part of the trap.

“An inexpensive detector that can be left in place and routinely serviced is needed to aid pest management professionals,” Ohio State University’s Susan Jones told the ESA. “Rutger’s do-it-yourself dry ice (frozen CO2) traps are a cheap and effective method for overnight surveys of potentially infested habitations.” An experiment in a 13-story high-rise apartment building in Columbus, Ohio compared (see You Tube video) 3 Verifi(TM) bed bug detectors per room with 1 CO2-generating dry ice trap per room and canine (dog) detection teams (2 dogs/room; same handler).

Verifi(TM) traps detected bed bugs in 11 of 17 infested rooms in the first 24 hours; and in 14 of 17 infested rooms within a week. Dry ice traps had similar efficacy. Dogs detected bed bugs in 19 rooms, including 3 rooms where neither visual inspections nor dry ice or Verifi(TM) traps detected anything. But the dogs were also not perfect, as each dog also missed 1 room rated positive for bed bugs. So the quest to capture bed bugs with carbon dioxide and other lures goes on.

Human ingenuity seems almost unlimited when it comes to traps. Carbon dioxide, heat and other attractants are all being tested with traps as varied as Susan McKnight Inc.’s Climbup bed bug trap and pitfall traps made from inverted dog bowls painted black on the outside. Rutgers’ Narinderpal Singh tested CO2, heat, and lures such as nonanol, octanol, 1-octen-3-ol, coriander, and spearmint with inverted dog bowl pitfall traps. CO2 had an additive effect with multiple-component lures in inverted dog bowl traps, and may be developed into an inexpensive monitoring system for detecting low levels of bed bugs. Trials with baited traps are continuing.

Both carbon dioxide and ozone show fumigant potential against bed bugs. Purdue University’s Kurt Saltzmann told the ESA of “Two devices capable of delivering ozone to laboratory fumigation chambers.” One device delivered a short exposure to high ozone levels, and the other long exposure to low ozone levels. “Preliminary experiments showed that adult male bed bugs were susceptible to relatively short periods of ozone exposure when high concentrations of ozone were used,” said Saltzmann. “100% mortality was achieved when bed bugs were exposed to 1800 ppm ozone for 150 minutes.” Low ozone fumigation is also being tested with 1-2% hydrogen peroxide for up to 72 hours.

Carbon dioxide (CO2) is used by libraries, museums, and others as an insect-killing fumigant. Indeed, dry ice (frozen CO2) to release CO2 gas is cheaper than washing and drying fabrics to kill bed bugs, Rutgers University’s Changlu Wang told the ESA. At an 80% concentration, CO2 kills all bed bug eggs in 24 hours (eggs are the toughest bed bug life stage to kill). A 50% CO2 concentration for 8 hours is sufficient to kill bed bug nymphs (immatures) and adults.

Wang’s CO2 fumigations involved filling Husky garbage bags 90% full of items such as mattress covers and fabrics, leaving little room for air. Then the bags were sealed with dry ice inside for several hours. Books, electronics, toys and other items damaged by heat treatments might benefit from the low temperatures created by dry ice treatments. However, for safety reasons Wang recommends wearing gloves and turning on fans for ventilation when opening many bags filled with carbon dioxide gas (fumigant).

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Ozone Oxygen (O3) Fumigation for Organics

June 29, 2010

OZONE, A NATURAL OXYGEN (O3; 3 oxygen atoms) molecule that can also be synthesized, is among many other things an alternative to fumigants such as chlorine, methyl bromide, phosphine, and sulfuryl fluoride. Modern day humans have an almost schizophrenic, Jekyll-and-Hyde relationship with ozone, alternately and simultaneously seeking to eliminate and preserve ozone in the environment.

At stratospheric heights 12-15 miles (20-25 km) above the Earth’s surface, in what is called the ozone layer, 90% of the planetary ozone swirls and drifts about in molecular clouds, protectively absorbing mutation-inducing ultraviolet solar radiation wavelengths (also linked to immune disorders, cataracts, skin cancer, crop damage). For that reason an international treaty, the Montreal Protocol, was enacted in the mid-1980s to protect the ozone layer against known and unknown (to be discovered in the future) molecules destructive to ozone. That’s the good Dr Jekyll aspect of ozone (with apologies to Strange Case of Dr Jekyll and Mr Hyde author Robert Louis Stevenson).

Closer to Earth’s surface, where the 10% of planetary ozone not in the upper atmosphere resides, metropolitan areas such as Los Angeles and Phoenix suffer from ozone pollution and come under regulatory fire from the U.S. Environmental Protection Agency (EPA) because what is good 12 miles high is harmful at ground level. In “America’s Most Polluted Cities,” Forbes.com’s (04.28.10) Tim Kiladze calls it “harmful ozone, a ground level gas that contributes to urban smog and inflames the lungs, causing shortness of breath, wheezing and throat irritation.” The American Lung Association State of the Air 2010 report web site formulates EPA ozone and particle pollution data for American cities and counties into searchable form.

So, will ozone gas as an alternative to ozone-destroying fumigants like methyl bromide create more ground level ozone pollution or help replenish and preserve the protective stratospheric ozone layer?

“Chemicals can have their seasons, just like fashions. What one age admires as fine, another will reject as folly, and a good example of this is ozone,” writes John Emsley in his 1998 book, Molecules at an Exhibition. “A century ago ozone was also something to worry about, and for exactly the opposite reason: it was thought there was not enough of it around. Ozone was deemed to be natural, wholesome and invigorating, and the very locations where its levels were highest proved this: up in the mountains and along the coasts…Such was the esteem in which the Victorians held ozone that they had generators pumping it into churches, hospitals, theatres and even their underground railways.”

At the 2009 Entomological Society of America (ESA) annual meeting in Indianapolis, ground-level ozone was back in fashion as an environmentally-friendly fumigant molecule (unstable; decomposes quickly). Methyl bromide (another natural molecule) faces demise as a fumigant under the Montreal Protocol for destroying ozone. And stored grain insect pests are becoming resistant to phosphine. Carbon dioxide, a waste gas exhaled by humans and a feedstock of sorts for green plants, has some fumigant potential but is too slow-acting and unfashionable as a warming greenhouse gas.

Though it is easy to pump ozone through hoses into grain bins, ozone does not penetrate the dense grain well and fumigations can last 3-10 days. Purdue University’s Marissa McDonough noted that the grain is more quickly disinfested of red flour beetles (Tribolium castaneum), maize weevils (Sitophilus zeamais) and other pests by physically moving the grain in layers exposed to ozone sprays in passing.

Potency, ease of use, and low cost make for a good fumigant, said Kansas State University’s Mahbub Hasan, who noted that phosphine, sulfuryl fluoride and ozone are all potential alternatives to methyl bromide fumigation for dry-cured hams attacked by red-legged ham beetles (Necrobia rufipes), ham mites (Tyrophagus putrescentiae), cheese skipper flies (Piophila casei) and carpet beetles (Dermestidae). Carbon dioxide was too slow, said Hasan, taking six days to knock out ham mites. An integrated (IPM) approach combining biological controls, cooling, pheromone traps, ozone and botanical fumigants may ultimately be devised for protecting stored foodstuffs.

However, ozone remains out-of-favor in the plant world. “Tomato plants may be more susceptible to wounding by caterpillar pests in ozone than in ambient air,” Western Illinois University’s Sue Hum-Musser told the ESA meeting in Indianapolis. “Several genes play important roles in plant defenses against the combined stress of ozone and insect herbivory. Increasing ozone levels cause damaging effects on the plant community, and insect pests cost billions of dollars to agriculture.”

Fashion is a fickle thing, and future ozone fashions will likely remain a twenty-first century Jekyll and Hyde muddle.