By Control of IL J. L. Ricard, T. E. See, and W. B. Bollen Oregon State University Incipient Decay Corvallis, Oreg. With Gases in Douglas-fir Poles t-200 THERMOBAROME TER D WOOD AL NE cr 00°A • 0 z METHYL BROMIDE- ALONE - cr 100 cr) METHYL BROMIDE AND WOOD cc Foreword a. In 1962, Messrs. 0. F. Hand and A. F. Wetsch, of the Bonneville Power Administration, began a study of gas diffusion systems for controlling I - decay fungi and insects in Douglas-fir and West- 10 20 30 40 50 ern Red Cedar utility poles. Many fumigants were MINUTES tested in that year, among them Chlorodane, Figure 1. — Evaluation of Warburg apparatus for study Chloropicrin, Ethylene Dibromidc, Vapam, Tc- of methyl bromide absorption by wood at 1.4°C. The break lone, Cresan M, Cyanogas and Methyl Bromide. in the curve for methyl bromide and wood is attributable Fungi and insects were killed by several of the to resetting the manometer. materials tested as confirmed by bio-assay tech- niques. Reported as among the most effective tested were Vapam, Cyanogas, Chloropicrin, and ERVICE LIFE of Douglas-fir poles could be ex- S Methyl Bromide. Following the work by Bonne- tended if they could be penetrated readily by fungicides with long-lasting effects. Incipient ville Power Administration, a cooperative research contract was established with the Forest Research decay is readily detected in poles (16), and the Overholts, Laboratory, Oregon State University, to evaluate common decay fungus, Poria carbonica chemical treatments for arresting decay in poles. is sensitive to fungicides (15). Douglas-fir heart- wood resists penetration by liquids, so we investi- The descriptih in this report of experiments gated an agricultural fumigant, methyl bromide, made by personnel of the Forest Research Labora- for penetration and retention; later on, ammonia tory should not be interpreted as a suggested treat- and sulfuryl fluoride were included for improved ment for routine operations. Compounds tested retention. are highly toxic to humans and should be applied Methyl bromide has a well-established reputa- by qualified operators who will follow directions tion in the food and agricultural pest control in- of the manufacturer. The maximum allowable dustries for its high penetration, relative safety, exposure over long periods is commonly set at and convenience of handling. Partridge (12) 5 parts per million (ppm) parts of air for sulfuryl tested it for control of oak wilt, Ceratocystis fluoride and 20 ppm for methyl bromide. These fagacearum (Bretz) Hunt, in 4-inch stems of black concentrations can be compared with allowable oak and white oak, with encouraging results. concentrations of the common chemicals hydrogen Jones (7) confirmed the effectiveness of methyl peroxide at 1 ppm, hydrogen sulfide at 20 ppm, bromide for that purpose under field conditions. hydrochloric acid at 5 ppm, and carbon tetra- chloride at 10 ppm. Acknowledgment is due Bonneville Power Ad- M. W. Belsher ministration for financial support provided under a Head, Research and Development Unit cooperative research contract. R. D. Graham, J. S. Transmission Design Section Mothershead and M. M. Wilson of Oregon State University cooperated. Bonneville Power Administration Portland, Oregon This paper was received for publication in May 1967. FOREST PRODUCTS JOURNAL Vol.m No. 4 45 The direct fungicidal action of ammonia has were used, no effort was made to ascertain the been known for some time (10). Roistacher, Eaks, actual amounts of gases absorbed in the Warhurg and Klatz (17) developed a procedure for the apparatus. In this instance, rather than actual control of various eenicillia on citrus fruits. volume of gases absorbed by the wood particles, Penetration of ammonia in wood has been studied the chief concern was how the pressure changes by several workers and applied to the plasticiza- compared with that of the single gases. If simple tion of wood (18). Sulfuryl fluoride was developed absorption occurred with the gas mixture as well for termite control (Al and its use is widespread as with the single gas, the same uptake pattern in the southern states. would be seen because the relative pressure of the two gases would be independent of the other, as Laboratory Experiments is usual in nonreacting gas mixtures (4). On the other hand, if solid synthesis were to occur in the Pure cultures of P. carbonica were obtained from wood in the same fashion as it does in wood-free the U.S. Forest Products Laboratory in Madison. systems, then a different pressure-change pattern These cultures were maintained on 2.5 percent would be observed, since some of the gas mole- malt extract agar medium, after testing of nutrient cules experience a change of state. at various concentrations (15). Room temperature Only one applicable cc -value, 0.009, was found was usually suitable for incubation (70°F. 5°F.). for methyl bromide (19). Its low magnitude com- Temperatures exceeding that range have a definite pensated for the lack of data available on its retarding effect on growth rate, and peak summer change with temperature. For ammonia, cc-values temperatures inhibited growth. at several temperatures were available from stand- Cultures exposed to methyl bromide in the usual ard reference manuals (9) and interpolation was concentration for 24 hours would no longer grow made for the particular temperature used of 1144 when placed in incubation under normal condi- milliliters gas per milliliter of water at 1.4°C. The tions. k-values obtained for the various flasks used The methyl bromide treatment was repeated on ranged from 1.2 to 1.7 for methyl bromide and wood cores freshly removed from an infected from 16.4 to 29.9 for ammonia, Th -e volume of pole, And similar results were obtained; no fungal the wood particles was measured by water dis- growth resulted with the samples exposed to placement. methyl bromide, although the untreated samples Figure 2 presents the data obtained with the showed profuse growth. For accurate dosage, the Warhurg respirometer. For the gases applied absorption of methyl bromide and ammonia in singly, the calculated k-values together with the wood was measured with a standard Warburg volume determination of wood particles allowed constant-volume respirometer. The change in pres- expression of the pressure changes in terms of sure within the closed portion of the system was microliters or milliliters of the respective gases recorded as a function of time in the presence and absorbed per cubic centimeter of wood. Nearly absence of wood particles of known volume. The 0.2 milliliter of methyl bromide and 1 milliliter Warhurg respirometer consists essentially of a of ammonia were absorbed by each cubic centi- manometer with one arm attached to a vessel meter of Douglas-fir heartwood. Ammonia absorr where the reactions under study are taking place. tion appeared to be complete within 30 minutes, The usual procedures were followed (20), with but with methyl bromide it continued for about some allowance for the particular gases used. 1 hour, although 75 percent of the absorption was All tests were made in three or more replicates completed within 30 minutes. at 1.4°C. to allow introduction of methyl bromide The absorption pattern, when both methyl bro- in the Warburg flask as a liquid. Vaporization mide and ammonia were present simultaneously, took place rapidly. Diffusion was measured readily, was appreciably different. A slower but protracted as shown in Figure 1, and approached equilibrium in and out of the wood particles in about 30 min- utes. All controls (thermobarometer, wood alone, and methyl bromide alone in addition to air in Table 1. - YIELD OF AMMONIUM BROMIDE SALT BY everp instance) followed the same pattern of fluc- MIXTURE OF METHYL BROMIDE, AMMONIA AND AIR IN SIMPLE SYSTEM. tuating within a range of 60 manometer units, but the methyl bromide and wood systems showed cH,R, a continuous pressure drop of more than 200 Ammonium Bromide manometer units. These data suggested that the CH,BR NH, Warburg apparatus was suitable for the measure- Volume Weight Volume Weight Weight Yield Wt. ratio ment of rate and extent of gas absorption by Douglas-fir heartwood, provided system constants cc Grams cc Grams Grams 04 were calculated. 800 3.9 200 0.1745 1.3977 34.6 2.23 The, constants were calculated tfor both methyl 300 1.488 200 .1776 1.1783 70.7 8.39 200 .992 bromide and ammonia separately. In those experi- 300 .2664 1.0600 84.4 3.72 164:1 .496 400 .3552 .3012 35.4 1.40 ments where both methyl bromide and ammonia AC • •-• 11.6 .1000— 1 I 1000 Solids formed in the simple laboratory systems always contained both bromine and ammonia, and 2—;" i decomposed between 163° and 225°C., as long as 800-- /I 800 the reaction temperature exceeded 30°C. and air _,--- was present. At lower temperatures, the formation . NH3 I- 4) U 2 of solids was delayed. In addition, with no air , u600 — , — 600 I , a: present, only compounds with low melting points 0 and lacking bromine were obtained. Table 1 shows ■- 3+ CH3E i r the yield of solids synthesized in various relative wi _....-,,o — 400 — (MANOMETER UNITS) 400 0 1,- a o ecooae,e40.-e ...cm, concentrations of methyl bromide and ammonia. CC -- — — — i i 7...- ''''' The highest yield, 84.4 percent, was obtained at WI) Z CH3Br ___ _ _ approximately 4:1 weight ratio. ° 200 _,,., .....e.o.c.s..ints-s-.• 6-n 200 3.F7 ,e ..,...,..... ,„,, The effect on wood strength of gas treatment X - 14,1e. with methyl bromide and ammonia, singly and VI CO 1 I 1 IQ mixed, was measured in terms of modulus of rup- ""t o till I 0 20 40 60 80 100 ture, through the standard static bending test (1) MINUTES with wood specimens 1 by I by 16 inches at 12 Figure 2.