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Preservatives treatment and field test monitoring of spruce pole stock: CCA and fumigant treatments
1990 - IRG/WP 3619
The fumigants trichloronitromethane (chloropicrin) and sodium N-methyldithiocarbamate (SNMDC) were used to treat red spruce pole stock, either CCA treated or untreated, through holes bored through the pole's center. The poles were analyzed for the presence of microorganisms immediately before ground installation and again after installation at a pole test site. Monitoring of fumigant movement in the poles was also performed after one year. Results indicate that both fumigants moved throughout the ground line regions of the poles, although less toxicity to the bioassay fungus was observed in the SNMDC treated poles. Reduced fumigant levels, and more sporadic diffusion was noted in the above ground portions of both chloropicrin and SNMDC treated poles although again chloropicrin exhibited greater toxicity to the bioassay fungus. Despite the variability of fumigant diffusion as determined by bioassay, no decay fungi could be isolated from the treated poles after one year. This was in contrast to high frequency isolation of decay from control poles.
A J Pendlebury, B Goodell

Methods for testing fumigant efficacies against termites
1986 - IRG/WP 1297
Methodologies for testing fumigants against termites are reviewed and factors needed to be taken under consideration for standardization listed. Toxicity should be defined by both direct exposure to the gas and under more practical "barrier" conditions which include test enclosures simulating abiotic surroundings of the termites, i.e. wood, nest material, etc. To observe latent effects, mortality should be recorded periodically after exposure until rates decrease to control levels. Fumigant efficacy should be reported as a function of concentration and exposure time, termed lethal accumulated dose (LAD).
N-Y Su, R H Scheffrahn

A laboratory evaluation of the fumigant, sulfuryl fluoride (VikaneR), against the Formosan termite Coptotermes formosanus Shiraki
1982 - IRG/WP 1164
A series of laboratory experiments showed that the fumigant sulfuryl fluoride (VikaneR) was effective against small groups of Coptotermes formosanus Shiraki exposed to the gas directly at temperatures from 20-40°C. At 10°C fumigations failed regardless of initial gas concentration. Very high or total mortality was observed at concentrations of 0.79 cc/L or higher. A second series of experiments was designed to evaluate Vikane's ability to penetrate the carton nest matrix. At 30°C penetration was sufficient to produce high mortality with gas concentrations > 1.06 cc/L. The results suggest that current dosage recommendations for the control of Coptotermes formosanus infestations in structures (4 lbs/1000 cubic feet) are too high and should be reevaluated.
J P La Fage, M Jones, T Lawrence

Fumigant movement in Canadian wood species
1984 - IRG/WP 3296
Pole sections prepared from seven Canadian wood species (Thuja plicata, Thuja occidentalis, Pinus contorta, Pinus resinosa, Pinus banksiana, Pseudotsuga menziesii, southern yellow pine) were fumigated with chloropicrin, methylisothiocyanate and Vapam and the rates of fumigant penetration determined. All three fumigants were applied directly into holes bored radially into the pole sections. Analysis for fumigants commenced after a few days at various sampling distances from the treating point. After three months the test was concluded. Methylisothiocyanate, diffused equally well upwards or downwards in the pole section from the point of fumigation in all wood species, and appears to offer the best potential of the three fumigants as a pole treatment in Canada. When applied directly, chloropicrin initially moved quickly but then the diffusion rate slowed somewhat. Upward movement was fastest in eastern white and western red cedar while downward movement was also rapid in southern yellow and red pine. Chloropicrin movement was rated as good in Douglas-fir but poor in jack pine. Diffusion of chloropicrin was severely retarded in lodgepole pine. In general Vapam movement was slow at first, and then increased with time. Diffusion rates for all wood species were similar except for relatively rapid upward movement in red and southern yellow pines.
J N R Ruddick

Effect of fumigant residue in aerated wood blocks on the spore germination of decay fungi
1991 - IRG/WP 2382
Fumigants are increasingly used in several countries for remedial treatments of transmission poles to increase the service life. The present study was initiated primarily to test the remaining toxic effects of spruce (Picea rubra) wood, fumigated with chloropicrin (trichloronitro methane) or MIT (Methyl isothiocyanate) after long period of aeration, on the spore germination of decay fungi. This study indicates that spore germination of decay fungi is more sensitive than mycelia for these fumigants. An assay involving spores could therefore complement the earlier proposed open and closed tube bioassays for assessment of remaining ability to prevent reestablishment of decay fungi in fumigated wood. This assay is sensitive both to bound wood residues contributed by the fumigants as well as to fumigant vapor.
J Bjurman, B Goodell

Prevention of non-microbial sapwood discolorations in hardwood lumber: chemical and mechanical treatments
1997 - IRG/WP 97-30137
Sapwood discolorations in hardwood lumber that are non-microbial in origin result from the formation of pigmented starch-like granules in ray parenchyma cells. These discolorations can be prevented by treating unseasoned lumber with an antioxidant (sodium bisulfite). Exposing unseasoned lumber to microwaves or treating logs with fumigants also will prevent these discolorations. Subjecting unseasoned lumber to mechanical stresses (compression and/or vibration) also prevents sapwood discolorations of non-microbial origin. A machine to mechanically stress lumber and thereby prevent these discolorations has been built and is being field-tested at cooperating sawmills.
T L Amburgey, S Kitchens

Three-dimensional modeling of fumigant distribution in wood poles
1993 - IRG/WP 93-30025
The practice of using fumigants to control internal decay has been widely accepted in the United States and has shown to be effect in control internal decay in transmission poles and other large wood timbers. Mathematical models were developed to simulate the chloropicrin movement in utility poles after treatment. The simulation results indicated that treatment of utility poles, using either traditional remedial treatment procedures or center-bore application procedures could provide long-term effectiveness in terms of eliminating existing infection and preventing further fungal attack. Controlled-release technology used in fumigant treatment was also shown to be potentially useful to reduce chemical usage and extend the protection period.
Jing Liu, B Goodell

Gelatin encapsulated fumigants for wood fumigations: Current research status
1985 - IRG/WP 3336
The fumigants chloropicrin (trichloronitromethane) and methylisothiocyanate (MIT) were encapsulated in gelatin as an alternative to liquid fumigant treatments for control of decay fungi in wooden utility poles. Gelatin-encapsulated MIT was stored for over 2 years under dry conditions without significant fumigant leakage. Gelatin encapsulated MIT and chloropicrin were released from capsules when placed in wood above the fiber-saturation point, although capsules were more permeable to MIT than chloropicrin. In field treatments, the addition of small quantities of water along with capsules was sufficient for fumigant release. Encapsulated MIT and chloropicrin treatments effectively reduced decay fungus populations in Douglas-fir utility poles.
A R Zahora, M E Corden, J J Morrell

Screening method to test efficacy of fumigants against fungi and preliminary data on the efficacy of sulfuryl fluoride
2014 - IRG/WP 14-20551
Methyl bromide is being phased out and there is an urgent need to find a suitable replacement that is effective in reducing exotic pest establishments via trade in wood products. Efficacy data for established phytosanitary fumigants were mostly developed for arthropods and nematodes, and limited information exists for plant pathogens. Increased interest in developing a fast screening process for fungi has prompted this work. Small scale sulfuryl flouride fumigations were conducted in 10 L chambers at six target concentrations (40-240 mgL-1) at 20 C for 24 h against 23 fungal species. Fungi were grown on barley/grain, which was placed in borosilicate glass tubes covered on both ends with a felt cloth to allow uninhibited gas penetration while minimizing the risk of fungal contamination. This allowed simultaneous testing of numerous species/isolates followed by 100% recovery of controls and without contamination of all other isolates exposed to six target sulfuryl fluoride concentrations. Preliminary data have shown that 13 out of 23 species survived the 240mgL-1 exposure. Additional research is needed to test efficacy against more isolates, and under different temperatures and exposure times before experiments closer to field conditions are conducted.
A Uzunovic, A Mukherjee, R Mack, P Elder, S Myers

Alternative fumigants to Methyl Bromide for wood products: Review of the development and preliminary tests of Ethane Dinitrile (EDN) in Canada
2019 - IRG/WP 19-30743
This paper reviews recent developments and updates in the search for alternative fumigants to ozone-depleting methyl bromide, for wood products fumigation. The absence of alternative treatments may result in significant market disruption if further restrictions on methyl bromide are imposed. This paper reviews key challenges and key attributes of an ideal fumigant and also the status of standardised test methods for evaluation of new phytosanitary treatments and efficacy data required to support adoption by the International Plant Protection Convention and national regulatory bodies. Recent detailed reviews of fumigants have recognised EDN (ethanedinitrile) as a promising product for use on wood products and other commodities. A review of key attributes, history of use and registration of EDN is shared as well as the most recent efficacy data obtained through recent research at FPInnovations. Preliminary data indicate that EDN is very effective against four tree fungal pathogens tested even at a low dosage and very short exposure time (one hour), and was effective against pine wood nematodes in logs within 24 hours of exposure. The lower temperature (10˚C) did not negatively affect the efficacy of EDN as often is the case with other fumigants.
A Uzunovic

Chemical Analysis of Southern Pine Pole Stubs Sixty Months Following Treatment with a Methylisothiocyanate-Based Solid Fumigant Stick
2019 - IRG/WP 19-30740
Methylisothiocyanate-based fumigants have been commercially used in the United States for over 35 years to control internal decay in utility poles and other wooden structures with little technological advancement. The most recently commercialized methylisothiocyanate-based fumigant is chemically known as dazomet. Dazomet is a free-flowing powder or granule that decomposes in the presence of moisture within a utility pole to release methylisothiocyanate. As a means to accelerate the decomposition to methylisothiocyanate, a copper solution can be applied to dazomet during the time of fumigant application. Laboratory and field studies conducted as part of the Utility Pole Research Cooperative at Oregon State University have demonstrated the long-term efficacy of dazomet. Concerns with applicator safety, inefficient copper-dazomet interaction, accurate dosing and a high potential for accidental spills, has led OSU researchers to develop several solid forms of dazomet. While long-term field testing by the OSU-UPRC has generated positive results, the prototype forms of solid dazomet had little commercial value. Recently, a commercially viable solid-stick dazomet product was introduced to the remedial wood preservative market to prevent and arrest active decay within in-service wood utility poles. To demonstrate the long-term performance characteristics of this solid form of dazomet, a field study was established in January 2014 in southern pine utility pole sections. At the fourth inspection conducted 60 months following fumigant treatment, chemical assay borings were removed at various pole heights and depths and analyzed for concentrations of methylisothiocyanate using GCMS. The 60-month results showed the concentrations of methylisothiocyanate were greatest in the pole sections treated with the copper amended solid-stick dazomet. When compared to previous chemical assay results at 12, 32 and 46 months following fumigant treatment, the 60-month results showed a sharp increase in concentrations of methylisothiocyanate in the copper amended solid-stick dazomet treated pole sections. The granular dazomet showed a slight increase in methylisothiocyanate production, where the unamended solid-stick and copper amended granular dazomet showed little change from 46 to 60 months of exposure. When compared to a methylisothiocyanate threshold value for decay fungi proposed by Oregon State University, the chemical assay results at 60 months indicated all fumigant treatments are effectively protecting the zone of fumigant treatment (15.2 cm below to 15.2 cm above groundline) of southern pine pole sections. However, the greatest protection within and above the zone of treatment was provided by the copper amended solid-stick dazomet treatment. Future sampling and chemical analysis of the southern pine pole sections are planned to monitor long term efficacy of the fumigant treatments.
D J Herdman, T Pope, R R Browning