Non-Toxic Fumigation & Alternative Control Techniques for Preserving Cultural/Historic Properties & Collections

Notes on a Conference

Karen Motylewski
Nov 1994

Technology & Conservation and the Harvard University Environmental Health and Safety Department presented a conference titled "Pest, Insect, & Fungus Management: Non-Toxic Fumigation & Alternative Control Techniques for Preserving Cultural/Historic Properties & Collections" on October 22-23. The conference was wide-ranging within the subject, and speakers came from the pest control industry, collections care and conservation research, and building engineering fields. All but one of the speakers I heard were exceptionally effective and interesting, but if you've been able to stay current in the museum pest management literature, most of the presentations served as a review of increasingly standard IPM practice and anoxic extermination strategies.

Most speakers talked the museum context, but information is readily applicable to libraries/archives. They answered some basic questions (e.g. Does freezing kill mold spores? No.) authoritatively and publicly. Speakers have not reviewed this summary--all mistakes are mine! The agenda was full, I've never had to use techniques other than preventive IPM, and there are sure to be wrong spellings and numbers. Many citations for pest management will be in CoOL or CHIN, which see. The conference abstract volume has a bibliography for each talk. I've my comments below are in brackets []; (sp) means I know I'm not sure of the spelling, and (?) means I know I might have got this wrong.

Non-Chemical Strategies for pest control

Mark Gilberg

Mark Gilberg, President, Conservation Processes Research, Nicasio, CA, reviewed the increasing number of non-chemical strategies available for pest control. These include low/high temperatures, modified atmospheres (nitrogen, argon, Ageless, CO2), and radiation. He described most of these processes and gave some parameters (temperature, RH, time, energy of radiation) for application. Most strategies have been adapted from food storage or agriculture. Their studies often neglect common collections pests and we have little scientific information about ramifications for treated library/museum materials. Gilberg noted that industry is often satisfied with less than 100% kill. All the strategies listed above can be effective if used at correctly. Again, scientific information about the variables is incomplete. Gilberg used early recommendations for freezing insects (2 days at 20° F) as an example. Apparently these derive from the capabilities of typical museum freezers and the normal work week (time off on weekends).

He pointed out many concerns and unknowns. Freezing is ineffective for mold and exposes brittle frozen artifacts to handling damage. CO2 research (from Rentokil) is unpublished and doesn't cover all stages of insect life; is there a long-term potential for formation of carbolic acid post treatment? Gamma radiation is ineffective for mold and can damage paper and other materials. Mr. Gilberg mentioned that commercial German pest control strategies include whole-building treatment with CO2: the building is "tented" and huge bags are inflated in the interior to reduce the amount of gas needed [the same principle can be used for small-scale anoxic treatments].

Considerations for choosing an insect control strategy include effectiveness, health and safety, specialized training needed, labor required, and issues of certification/registration. Apparently most non-chemical insecticidal strategies are not covered by legislation and are therefore illegal[!].

Building & Institution-Wide Pest Management

Gary Alpert

Gary Alpert, Entomologist for Harvard University, discussed the critical importance of building-wide or institution-wide pest management. It's usually unsuccessful to treat infestation symptomatically. He breaks pests into 4 categories:

  1. those that specifically attack objects (e.g. powder post beetles, odd beetles, tineola;
  2. general building infestations (e.g. silverfish, dermestids, psocids, mites);
  3. those that attack structures (e.g. carpenter ants, anobeids, termites, carpenter ants, yellow jackets); and 4. occasional invaders (e.g. spiders, flies).

In all cases, pest management must be institution wide, not limited to the individual or infestation. Item treatment may be necessary, but isn't sufficient.

Understanding insect life cycles and habits is important in IPM. For example, look at any dumpsters in close proximity to a building. They should be self-contained, sealed, protected from rainwater. Check under dumpsters and look for standing water (as attractive pest habitats). The odd beetle, for instance, is found in conjunction with insect collections in museums; it eats protein and attacks animal material, including dead bugs, silk, etc. Many insects burrow or tunnel out, not in--holes don't indicate feeding activity, but frass indicates active infestation. Holes can provide routes of reinfestation. Many bugs feed on protein. Look to see if rodenticides are in use; carcasses (usually in walls) provide food sources and are hard to find and eliminate. Dermestids are very adaptable to environmental change; when stressed, populations molt to smaller sizes, then can enlarge again. Hairs on the surface of the insect are shed with the molt and are common allergens. Anobeids are attracted to moisture, as in wood beams or framing damp from leaks. For termites, look for adjacent root systems and buried wood from earlier construction.

Glue boards or sticky traps need to be appropriate for the suspected insects, and placed in attractive environments or on likely routes. [Roaches, for instance, like close, dark spaces; mice and rats usually stick close to the walls and follow each other's scent trails. Place traps accordingly.] Don't forget to consider frames, objects in museum shops, inter-wall, floor, or ceiling spaces, and offices as well as more obvious collections. African wood was mentioned as a prime site.

Mold and its Life Cycles

Mary-Lou Florian

Mary-Lou Florian, emerita conservation scientist, Royal British Columbia Museum talked about mold and its life cycles. In very brief, she stressed the importance of accurate language. What most of us call "spores" are really conidia; hyphae and mycelium refer to elements of active growth; growth is conidiation; mold is fungi [I think]. Conidia have 4 stages: maturation, dormancy, activation (potentiation of growth), and germination (initiation of mold growth). Possibly we could prevent activation by preventing exposure of spores to a variety of phenomena including surfactants, detergents, acids, organic solvents, and heat or cold outside moderate ranges, but little research has been done on this stage of fungi. Most is done on the vegetative or active growth phase. Once activated, fungi can germinate when conditions are favorable (above 70% RH).

The speed of germination and growth depend in part on the moisture level of the object and the environment, how long they have been elevated, and at what temperature. Apparently the reliable research literature indicates that mold will really not grow below 70% RH. Temperature and RH do affect vegetative growth; they can determine the production of pigmentation. Experiments with aspergillus niger demonstrate that the rate of germination after 2 days at 60° F/95% is analogous to that at 60°F/80% after 32 days. [Clinical experience with mold growth at lower RH must be under circumstances where the microenvironment produced by moisture content of the object is at higher than ambient RH, or where RH is inaccurately measured, in variable microclimates in a larger space, or after an excursion to 70+% after very long exposure to RH between about 65% and 70%?]

Most of the common fungi we see in collections are asexual. These include aspergillus, cladosporium, pullularia, and penicillium. Asp., clad., and pen. are found in habitats from the arctic to the tropics, although proportions of each differ with different climate regions and between indoors and outdoors. The same types are found on nearly all museum materials around the world and are pretty much substrate independent.

Low oxygen environments are not effective for mold control. Conidium maintenance [for all types?] requires only 0.2% oxygen; it's an impractical level to reach.

Differing vapor pressures inside and outside objects impact germination and vegetative growth. Varying RH at one temperature produces differing equilibrium moisture content (a critical variable in mold growth). Moisture absorption is [always?] faster than desorption. Curves for aged and new materials differ under the same conditions. The literature suggests conidia must absorb moisture from the substrate (cannot absorb moisture from vapor, i.e. humid air), but research is inconclusive. Wool will support germination at about 12% water content, while cotton requires only about 8%. [Controlling RH and temperature thus control the moisture content of the object, and consequently germination.] [So vacuum freeze drying will kill active fungi, but will not kill dormant conidia.]

We need a lot more research to determine the possible relationship between conservation treatment protocols and subsequent mold growth. For example, we don't know if by-products of fungus metabolism are or should be removed during treatment; we don't know if or which treatment chemicals activate conidia. It's very important to document treatments and post-treatment conditions (wherever possible) accurately to explain and/or track the impact of treatment on mold growth.

Subterranean Termites

Nan-Yao Su

Nan-Yao Su, Professor of Entomology at the U. of Florida, Ft. Lauderdale, talked about tracking and controlling subterranean termites by baiting and monitoring. He noted that world wide, $1.2 billion is spent on termite control [!]. Termites will tunnel through masonry and stone to reach wood. Dr. Su color stained captured termites and re-released them to map the pattern of infestation and foraging in a building complex, using drilled postholes as collection and re-release points.

The pattern of activity allowed the strategic placement of baited pesticide for fullest kill, using positions near nest sites, underground roots and other reservoirs, and along the major underground entry routes of the termites. To be effective, bait should be toxic, have growth or chitin inhibitors, or contain some other destructive material. It must be slow acting, so it can be transported back to next sites to affect termites by secondary exposure. Dr. Su has participated in development and field tests of a termite monitor/bait station called Centracon, expected on the market in 1994-95.

Climate Control in Historic Structures

Tom Newbold

Tom Newbold, an engineer with Landmark Facilities Group, Norwalk, CT discussed some principles of planning and design for climate control in historic structures (in part as a strategy for pest control). He advocated a planning team including architect, conservator, curator, and engineer. He noted that humidistatic control [principles developed by Landmark with the cooperation of Shelburne Museum and Rick Kerschner] for unoccupied buildings in the NE in winter) requires, among other things, double glazing, all-air heat for temperature control, a perimeter U-value of greater than 0.5, good attic insulation, and a mechanical humidity source (ultrasonic, nozzle, or spray mist). He also noted that particulate filtration to 95% (ASHRAE standard) effectively controls inflow of most bacteria and conidia.

Tom gave the following guidelines for retrofitting climate control:

HVAC Systems & Disaster Prevention

Martin King

Martin King, President of martin Churchill Assoc. and advisor to the National Institute of Fire Restoration outlined guidance for maintaining HVAC duct systems and lowering the risk of disasters. Recommendations included: consider the relationship of HVAC and emergency preparedness (especially with regard to ventilation). Design for prevention; e.g. use unlined metal ducts rather than fiberglass lined to limit air pollutants. Normally well-designed air distribution systems will prevent mold and bacteria growth, but operational failure can spell disaster. Single zone systems are the easiest; components consist of air supply, filters, supply conditioning mechanism(s), distribution, dampers and returns, and exhaust. Consider both the entry point for replacement air and return duct paths. Choose locations to limit contamination from interior and exterior sources.

King described major components of air distribution and duct systems.

In developing maintenance procedures for existing systems:

Rodent Control

Bruce Colvin

Bruce Colvin, Bechtel Corp. Scientist, talked about rodent control and managed to be funny and informative. He pointed to a natural cycle for rodent populations determined by weather/quality of habitats/(human) social and economic factors/population dynamics [I didn't note whether these were rodent or human; could be either]. [Control of these pests becomes even more critical with the emergence of such human diseases as Lyme disease and hantaviruses.] He identified as common pests

As with insects, understanding life cycles and habits are important for IPM. 95% of rats live only 6 months., but reproduce rapidly. IPM has 4 governing principles: predictive, pro-active, integrative, and effective.

  1. Educate: policy makers, resource allocators, and the contextual "society."
  2. Provide good sanitation procedures. Have enough trash receptacles, empty them often, choose rodent resistant containers. In particular, avoid rust, drainage holes (mice can get through any opening larger than 1/4"), and lidless containers. Inspect replacement dumpsters at each exchange. Inspect and clean around containers daily. Use liners. Centralize trash accumulation. Pick up interior waste daily during daylight--not overnight.
  3. Rodent proof entries, doorways, masonry or other structural openings. Keep doors closed. Inspect loading dock doors frequently, and make sure they seal tightly at bottom. Check for openings around utility conduits and entry points; seal them after eliminating infestation. Check footing joins. Leave 8-10" x 7"-deep gravel inspection area around footings. Don't use dense plantings in landscaping--"landscape architects are the enemy."
  4. For poison and trapping programs, remember rats mistrust anything new. Zinc phosphide is an acute toxin; bromethalin and calciferol are subacute. Don't use "first generation" anti-coagulants for a chronic problem--rodents habituate and develop genetic resistance. If using "2nd generation" anti-coagulants, rotate brodifacoum and bromadiolone for the same reason. Paraffin bait blocks are good for damp situations. If kids or pets are present, use closed bait stations. Traps include "snap-trap," multi-catch, and glue boards. Keep records of placement and clean traps and bait stations frequently. It's critical to keep good records of trap/bait location and to use diverse methods, shift placements, and use effective types of bait. Try to reduce numbers by trapping before applying poison and sealing entry points.
  5. Enlist community participation.
  6. Develop a managed, coordinated program, including for contractors. Specify areas to be treated and frequency. Require diversity of methods; perimeter and interior control; intensive documentation, surveys, mapping, and inspection; and good record keeping.
  7. Schedule activities, and check staff or contractor performance against the schedule. Quality assurance depends on such checks.
  8. Remember the importance of planning, scheduling, communication and coordination, diversity of methods, and monitoring.

Heat, Cold, and CO2

Tom Strang

Tom Strang, Canadian Conservation Institute talked about heat, cold, and CO2 as insect control approaches. [I've never heard anything less than a comprehensive, creative, and entertaining talk from CCI. Tom is all of the above, for anyone looking for speakers on preventive conservation.] In choosing or evaluating programs, consider efficacy, risk, availability (in context of resources), and cost. The following chart represents the budget profile of most museums:

   |___  1960s acquisition
   |   \
 $ |    \
   |     \_____  1990s collections maintenance

[I wish I could represent Tom's charts and graphs. Another graphed high and low temperature extermination regimes against reference temperatures for a good day of skiing in Aspen, a good day at the beach and a bad day in Bangladesh. Non PC, but graphic and funny.]

Furniture warehouses heated their stock for disinfestation until about the 1920s. Hot water washing kills clothes lice, many fungi. Heat works faster than cold. Extermination depends on rate of heating/cooling, duration, and magnitude. Strang recommended l week at -20° C or below (see Michalski, ICCOM preprints 1993).

Carbon dioxide is efficacious, low risk, available and cheap. The research literature suggests 30 days in CO2 at 20-29° C.

Low-Oxygen Environments

Gordon Hanlon

Gordon Hanlon, Associate Conservator, sculpture and dec arts, J. Paul Getty Museum. The Getty has been exploring low-oxygen environments with a number of gases, including Ar and N, and with Ageless oxygen scavenger. Gordon described several approaches tested.

Dynamic system

Uses gas and humidity control in a low-permeability bag surrounding the object. In these systems the container is purged using a gas to push oxygen out, the gas is humidified to the right level for the object and the bug, the bag is sealed, and gas flow maintains a low-oxygen environment under positive pressure.

Basic steps:

a. Make bag [used in all low-O strategies]. Minimize the amount of gas and plastic needed by shaping the bag to conform at least roughly to the object geometry. [Alternatively, use interior gas-filled bag to reduce bag volume.] Use as few seams as possible. Use low-O permeability plastic. Aclar (sp?) is used by Getty for bag-making; alternatives include Cryovac (?) and MarvelSeal, all of which will form heat sealed seams. Bulldog clips are good for temporary seams for shaping. Heat seal seams (numerous tools exist, low end is a tacking iron). Create gasket for gas inflow, use Swagelok fittings (these use an o-ring and washer seal). leave about 1 foot of seam open for purging.

b. Humidify gas using water bubbler.

c. Purge bag. Gordon mentioned 8x, to 0.1% O (oxygen gauge needed). Getty uses a Teledyne oxygen monitor, approx. $800.

d. Seal bag (you can re-use bags).

e. Slow gas flow to "trickle" and maintain for 14 days (Getty protocol) at 0.1% O. Small objects may not require continuous gas flow, but only a monitor will tell you.

Static system

Uses Ageless inside a low-permeability bag (see above). Ageless is chemically treated Fe in a permeable package; it reacts to bond oxygen in a sealed container. Different forms of Ageless work at different RH, and quantity needed is dependent on volume of bag. Reaction is exothermic. Don't put Ageless sachet in direct contact with object.

"Ageless Eye" is a pellet that changes color in response to oxygen and so serves as a simple oxygen monitor. Many people report problems with accuracy. Ageless Eye ages, must be maintained in an oxygen free environment before use.
Hybrid system

Relies on Ageless, but uses a nitrogen purge (with no continuous supply.

Alternatives to bagging:


William Robinson

William Robinson, Director, Urban Pest Control Research Center, Virginia Tech. talked about polyborates as a control for termites and mold [?, no details given]. These are water-soluble borates naturally present in some proportion in many woods; to be effective, the application must exceed natural level of borates. [This may help explain why some wood boxes (e.g. pawlonia, cedar) have pest control properties.] These are reported to be cheap, environmentally safer than many other insecticides, but data on effectiveness and insect-lethal quantities are limited. Wood needs to be unaged and untreated to allow borates to penetrate. Penetration/diffusion in wood is governed by the presence of free water and wood structure (each is different), and method of application. Boron is chemically very stable.

Dr. Robinson showed the cellular and microscopic structure of trees, which was helpful for understanding diffusion of water and solutes through wood, but needs illustration. In short, live trees have about 35% wood moisture content (WMC); structures of wood normally contain about 12-16% WMC, seasonally variable. Application methods vary--surface application gives slow diffusion. Pressure injection is very efficient, limited by volume applied, moisture content of the wood being treated, depth of injection. Complete diffusion is not critical for extermination because insects move through the wood. Toxicity and penetration are not necessarily linked. 1,000 ppm boron or more is needed to control powder post beetles or "ordinary house borer." [Although the point was not specifically addressed, borate injection seems to be preventive rather than curative.]

Clothes Moths

Mary-Lou Florian

Mary-Lou Florian gave an instructive case history of clothes moth infestation at the Royal BC Museum (13 stories of storage) illustrating the difficulty and necessity of tracking infestations to their source and treating them as a building-wide problem. Surveys, documentation, tracking, and documentation of actions are essential for success in controlling museum pests. [I don't have good notes here, so this is an overview.] A pest survey revealed moth larvae in sheep skulls. This was addressed, and moths recurred. Pupae were then found in the floor and wall joint below the original location of the skulls (where larvae had dropped on the floor and crawled to pupate). These were handled, and there was another flurry of moths. The source of these was finally tracked to stairwells, through moths in spider webs.

The moral is look carefully to find all sources, and all stages, when trying to control an infestation. Use monitoring methods, trap sites, bait, etc. where the pest will naturally go (e.g. silverfish can't smell or see, but they sense moisture). Remember that local extermination, used alone, can drive pests into new areas of a building or collection.

Clothes Moths

Gary Alpert

Gary Alpert gave additional case data to re-inforce IPM principles. An infestation of clothes moths at an academic department at Harvard turned out to have its source in an oriental carpet too large for an office. Larvae were found where it was up against a wall or chair leg in an office--these moths like dark, close spaces. Another case revealed moths in rolled, stored carpets in the basement of a historic house, again, because these insects like still, dark, close spaces. Moral, look in places the particular insect likes to live or breed.

Health and Safety Issues

Mary Corrigan

Mary Corrigan, Environmental Health and Safety Department, Harvard, gave an excellent talk on health and safety issues in re current and historical pest control strategies that may impact contemporary collections and caretakers. She noted that Goya and van Gogh's individualistic senses of form may have been due to optic nerve swelling brought on by lead poisoning. She noted the current $450M suit against the trustees of the New Museum of Modern Art by former and present employees alleging permanent health damage from mold exposure [see CoOL for a citation to a news article on this in Acts Facts or one of the other arts safety newsletters].

Ms. Corrigan identified exposure risks conservators should remember as intermittent use; self-employment; non-occupational exposures; unknown materials; irregular work schedules; inadequate labelling; and historical gaps in knowledge (as in the case of toxins used in taxidermy. All may lead to unrecognized exposures to toxic substances in potentially problematic combinations. Routes of exposure include dermal; ingestion; inhalation; and injection. Severity of risk depends on degree of exposure; multiple exposure and synergism; risk status (e.g. medications, smoker, pregnant); and total body burden (e.g. alcohol consumption, smoking).

Conservators can manage risks by inventorying/evaluating all of the above to know what you're exposed to. Inform yourself, employers, and employees about exposures and dangers. Use your consumer power: ask for MSDSs and ingredients lists. Use precautions: protective equipment, ventilation, personal sanitation (washing, limits on food in workplace). Store and dispose of toxic or potentially toxic materials safely (isolate them, use appropriate containers, get rid of unknowns, dispose of wastes according to legal and safety guidelines). Substitute safe products when possible. Use a HEPA vacuum for lab clean-up; dry-mopping and sweeping can increase exposure to toxins and allergens by moving them into the air.

Information and help are available from National Pesticide Telecommunication Network (1-800-858-PEST); Center for Safety in the Arts (212-227-6220); and Pregnancy Environmental Hotline (1-800-322-5014). Information is also available from OSHA standards; NIOSH evaluations, and the Consumer Safety Commission.

Pheromones and Attractants

David K. Mueller

David K. Mueller, Owner, Insects Limited, Inc. spoke about pheromones and attractants for insects in the context of the webbing clothes moth (Tineola bisselliella). Of general applicability: placement of attractant traps is important. You want to minimize attraction to the collections from the exterior. Don't put attractants near air ducts (which can redistribute insect populations). Attract insects towards traps, away from building entry points like windows. In "manipulating insects" you want to consider life cycle, behavior of insects, natural attractants. If you can identify natural attractants (e.g. tobacco for cigarette beetles) these may be effective lures. The abstract for this talk is relatively comprehensive.


Robert McComb

Robert McComb is a scientist at the Library of Congress Research and Testing Office. Dr. McComb agreed that insect or mold infestation should be treated as a whole-building problem. He [unlike most in the conservation field] believes strongly in chemical fumigants, which he has used successfully throughout his career. He acknowledged that with increasing knowledge about the human toxicity of these chemicals they have gone out of favor, but said that he himself has not experienced toxic effects to date. McComb favors ETO for small infestations, and recommended extensive flushing (27-30x) of ETO chambers post treatment, at [unspecified] intervals, under controlled RH. He favors thermal fogging (using 60-65° C?) with ortho-phenylphenol (opp) in the case of extensive mold outbreaks, preferably for 5 sequential nights. He recommends that no one with respiratory problems or other vulnerabilities be allowed in an opp fogged building for 30 days. EPA has recently identified opp as a carcinogen. McComb notes that opp softens resins/varnish, including those on some book covering materials (this will reharden). He recommended against the use of thymol because it is too expensive; he also noted that it is less efficacious than opp and that its toxicology has been established as a conservation hazard for a longer time.

Dr. McComb had a helpful hint about dehumidifier use: position the unit high in a space to dehumidify at the level of the warmest air.

A participant from the Canadian housing bureau commented on the McComb presentation and offered the following advice: use only bleach or ethanol for mold clean-up; address source control first [i.e. control any source of additional conidia]; lower temperature and RH and improve air circulation; start cleaning only after active mold growth is controlled.

Implications of Disinfestation Treatment on Museum Artifacts

Robert Koestler

Dr. Robert Koestler, Research Scientist at the Metropolitan Museum gave still another excellent talk about the implications of disinfestation treatment on museum artifacts. He laid out as a governing principle in treatment choice the concern for the well being of artworks. His major topics were

He used an egg tempera on masonite panel as a case example of severe mold presented to the Metropolitan lab for treatment. His testing and decision-making protocol included analyzing the support, size, ground, medium, pigments, and surface coating to produce a "map" representing the components of the artwork and their conjunction (support, support + size, support + size + ground, etc.). This was cut into test strips to test potential treatments for their impact on the work itself. Testing included visual and microscopic (?) inspection, photo-spectrometry, and Fourier transfer to evaluate visual color, gloss, cracks/bubbles, topographic change and blanching both subjectively (using 2 educated evaluators) and scientifically. Evaluators examined random-sampled squares on a grid matrix and judged the subjective degree of change post treatment on a 5 point scale. As I remember Vikane, Lysol, Biomid 66 and several other treatments including nitrogen were used. Chemical treatments all produced visible effects, nitrogen did not. [I believe there is a paper in JAIC that details the research project.]

On the basis of the tests, oxygen deprivation was chosen as the treatment strategy, using a low gas permeability bag, with constant nitrogen [presumably humidified] flow to evacuate the "chamber." Ageless was used to maintain/back up oxygen control, and argon humidified through a water bubbler was introduced to replace the nitrogen. The Met found that a portable heat and pressure sealer produced the best seams. Koestler noted that argon sinks to produce a stratified microenvironment; this may be important in the treatment of large objects or vertical geometry. The technique requires an oxygen monitor; the Met's instrument is roughly $2500.

Argon is reported to show 25-50% faster kill rates [for mold??] than nitrogen alone would produce. Dr. Koestler reported that Russian research has demonstrated that mold viability is "compromised" under "sustained" conditions of "low RH" and "low-O." [None of the factors in quotes was detailed.] He noted that CO monitoring is an indicator of insect respiration (hence viability). He also noted that length of treatments documented in the research literature should only be used as general guidelines--treatments need to be designed for the specific situation and object.

Ecosystem Management

Tom Dunn

Three short papers were presented on industrial research into biological controls and genetic engineering in pest management.

Tom Dunn, a research scientist from EcoScience Corporation in Worcester, MA talked about "ecosystem management" in the context of roach control. His company is testing a product called a "Biopath" chamber seeded with metarhisium anisopliae, a fungus that attacks many insects. Roaches travel through the chamber [designed to meet their preference for close spaces] and brush their backs against the fungus; they then travel back to their colonies, where mutual grooming spreads the infection. [Ycch!!] The point is that a natural pest of the species is used in conjunction with the species habits to produce kill-off.

A participant asked about the accuracy of the data on the Biochamber's performance, reporting that he had used it in field trials, and found it only produced approximately 70% kill--not enough to control a small-scale roach populations. The relationship between lab and field findings was questioned (without answer). Later in the program Dunn suggested that traps might alter performance in storage or shipping; no satisfactory answer was available.


Michael Riuzzo

Michael Riuzzo, a market development specialist from Miles, Inc., in Sicklerville, NJ, talked about a new class of chemical termiticide, chloronicotinyls. A commercial product called imidacloprid (tradename "Premise") is being developed by Miles. This is a new chemical related to nitromthylenes, a "chlorinated-nicotine-like molecule." It is reported to have a new mode of action and to be environmentally safer than standard insecticides. Unlike the more conventional pyrethriods, which block sodium uptake, or carbamates, which attack acetylcholine esterase, this apparently affects "post-synaptic binding to the nicotinergic acetylcholine receptor sites." [As a non-biologist, I interpret this to mean that these biocides all attack the bug nervous system profoundly, but imidacloprid does it in a way not previously tried in insecticides.]

The chemical is reported to be effective at concentrations less than 1 ppm; it is non-repellant; palatable to termites; odorless; slow acting; and works in the presence of mold. It can be used to treat soil for subterranean termites. [See Su, above, for placement considerations.] Riuzzo estimates 7 days to active reduction of a colony. Sand, clay, and muck demonstrate different kill times (the best achievable is apparently 14+ days. Premise is currently undergoing environmentally approved testing, has been found to control some species of termites for 4+ years, Formosan termites for 2 yrs.

Rodent and Bird Control Strategies

Michael Godfrey

Michael Godfrey, Director of Research and Development for JT Eaton and Co., Des Moines, IA, discussed (primarily) rodent and bird control strategies. He mentioned that second generation anti-coagulents (see above) will kill rodents on one ingestion. Single wires stretched across a sloped roof at 50-ft increments will disrupt bird (e.g. pigeon) landing abilities. He warned that anyone cleaning up after birds or rodents should wear a respirator. He warned that in a survey for rats, the surveyor should look at roof level as well as low (for roof rats). Diatomaceous earth is effective as an insecticide--it abrades the insect cuticle, desiccating the bug. He advocates snap traps or glue traps for rodents. Place them on normal travel routes (e.g. close to walls).

He recommended exclusion as the primary aim of rodent and bird control. Pest proofing should be integrated into building design (e.g. roofs, seals, ledge angles, etc.). Bats can be kept out by plastic netting. Mr. Godfrey described a strategy of locating the exit hole (a colony will typically use one), fixing plastic net over it, but leaving the bottom open for 48 hours or so. At the end of that time, most or all of the bats in the colony will have left, crawling down under the unfastened net, but will not be able to return through the same opening. At that point, seal the bottom. [I have heard another pest control expert advocate stationing volunteers all around the perimeter of a building at dusk to sight the exit hole for a colony.] Pipe openings, for example at soffits, can also be sealed with net.

IPM in Museums

Tom Strang

Tom Strang gave a second paper on IPM in museums. He referenced John Robin Saul (?), A dictionary of Aggressive Common Sense, as an entertaining sourcebook. He referenced the new CCI chart for integrating and planning preventive collections care [see the 1994 (Ottawa) IIC-CG Conference Preprints for an excellent summary]. Pest management is 90% sanitation, but it can be hard to initiate change in any institution ("All change is hard"). [The framework for preventive conservation or IPM follows in shorthand.]

Framework: 9 agents of deterioration; 3 levels of control; 5 stages of control are identified in the schema:

Deterioration: Physical forces; thieves/ vandals/displacers (e.g. staff use); fire; water; pests; contaminants; light; incorrect temperature; incorrect RH.

(Pests: include vermin, insects, and mold.)

Levels of Control:
Stages of Control: Avoid; block; detect; respond; treat/recover


Mark Gilberg

Mark Gilberg's second paper was on Ageless for low-O environments. He described Ageless as iron treated with zeolite, NaCl, and C to make "an oxidation machine in a gas-permeable package." (The same product is used for rapid warming products.) Speed of reaction is controlled by product modification and moisture (product numbers refer to different reaction rates and humidity windows).

Ageless Eye was reported to be troublesome; it has a limited shelf life and requires anoxic packaging.

Appropriate films suggested were saran-coated nylon; polyvinyl alcohol-based film; and MarvelSeal. Polyethylene and polypropylene are too gas permeable to be used. Sealers span a thermal impulse sealer (c. $500, constant-heat type = c.$2,000) to hand-held sealers (tacking iron, pressure iron). Match film heating properties to the tool.

Match Ageless type to RH conditions required. Make the bag geometric in your mind's eye to measure the volume of the bag L x W x H divided by 5 = mils oxygen (close-enough estimate). Calculate the necessary amount of Ageless. Over-compensate if you're worried. Flush with gas (humidified as necessary). A vacuum pump speeds the process. Advantages are safety, easiness, absence of residues, absence of long-term affects on treated objects. Limitation is the size of objects that can be bagged.

Mr. Gilberg showed the soft Rentokil mini-bubble for low-O treatments--it was about the size of a card table covered with a cloth; you can build a pvc scaffold to maintain dimensions. The bubble includes and inspection windows and gaskets, but fittings must be user-modified to accept a nitrogen line. Cost is about $500. Rentokil also makes a "one off" bubble or aluminized film in about a cubic meter size. This includes a window, and can be reused, with care. Cost is about $80.

Professional Contractors

Peter Wonson, Sr.

Peter Wonson, Sr., President of New England Pest Control Association and General Environmental Services, Inc., Boston, talked about getting the best from a professional contractor in pest control. The industry has undergone an evolution from "spray and pray" to "the thrill of the kill" to "the rapture of capture" (i.e. from generalized poison applications through targeted toxins, to traps and attractants). IPM is now recognized as the responsible approach.

He recommended


J. Bryan Blundell

J. Bryan Blundell, Product Development and Tech Support, Preservation Resource Group, Rockville, MD, talked about borates for wood protection. He recommended sticking with one supplier and making sure they know your site and problems--a team approach between supplier and purchaser is the best strategy.

Borates have apparently been used for 40 years in Australia and Europe. They have many advantages, including low human toxicity, no odor, etc.). Formulations vary in moisture content and target insect. Apparently borates kill necessary microbes in the "insect gut" and kill mold through "over-fertilization." Products include Bora-Care (borate/glycol liquid); Tim-Bor (dry powder); and Jecta (spot treatment). Borates are approved for food handling and storage areas. They're good for interior applications and chemically sensitive areas. They can be used for carpenter ants, termites, borers, beetles, and wood fungi. They can't penetrate paint or sealant coatings, chemical stains, etc. They have limited life expectancy in contact with ground or soil (water provides a migration route for borates out of wood). Application can be by spray, mist, injection, brushing, foam or fog (no heat required).

Applicators should use good protections (gloves, respirator, etc.) and good sanitation. Water repellant products are marketed for collateral use with borates: Co-Pel mixes with Bora-Care; this permits removal and retreatment, but is used at roof level only. "Impel Rods" are solid borate for installation in drilled holes; wood plugs are used over the holes. Blundell recommended these be used with Jecta for best results. You can also use Bora-Care or water soluble borate, but results are not as good. Impel rods are recommended for sites vulnerable to wood rot. Borates are mostly used for pretreatment. See Sheetz and Fisher (sp?), National Park Service Tech Note #4 on exterior woodwork and borates for good information.

Karen Motylewski
Northeast Document Conservation Center
100 Brickstone Square
Andover, MA 01810
508-475-6021 fax
Use KM in subject field

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