WOOD SOIL CONTACT CULTURE TECUNIQUE 129 



Blocks Fungi 



A LenzUes trabea fi,()\l Y.V.I.. 



B Porid incnissdla #563 F.P.L. 



D Leiitiniis Icfideus * 534 F.P.L. 



E Poria microspora # 106 F.P.L. 



F Poria luleofibrala (Baxter) 



The distortion and shrinkage of the blocks can be used as a visual confirma- 

 tion of the weight loss due to decay. 



The more recently developed Greensalt O is similar to the K salt. The 

 treating solution of this salt mixture is composed of copper o.xide, hydroxide 

 or carbonate, chromic acid anhydride, and arsenic acid in percentages based 

 on the chemical equivalents of the copper, chromate and arsenic salts in the 

 K salt solution. The toxicity from the wood-soil assay of Greensalt O is 

 given in Table 4 for fourteen fungi and for three concentrations of the pre- 

 servative. The effectiveness of the Greensalt O treatment of wood is ap- 

 parent from examination of the toxicity index. The weight losses due to 

 decay of the untreated reference blocks indicated in general that conditions 

 for decay were again very severe, but the reference blocks exposed to the 

 fungus Lentinus lepideus were protected by their proximity to the treated 

 specimens. As previously pointed out, the fungus Lentinus lepideus does 

 not tolerate even slight concentrations of copper, which is a major component 

 of the Greensalt complex. 



The fungus Poria incrassata was again shown to be the least affected by 

 the toxicity of the preservative. The toxicity index for the blocks treated 

 with the highest concentration of the preservative was 94% after 16 weeks' 

 exposure to this organism. In view of the excellent field record for the 

 equivalent K salt preservatives ratings 90 to 100% by the toxicity index 

 would be satisfactor}^ Additional data will undoubtedly determine the 

 limits of the toxicity index. 



At the end of the 24-week period, the fungi BTL U-11, Lenzites trabea, 

 Tratnetes serialis, Poly poms vapor arius, and one strain of Coniophora cere- 

 bella caused slight decay of one or more blocks treated with the maximum 

 concentration of preservative, the fungi Lenzites trabea, Coniophora cerebella, 

 and Trantetes serialis were still capable of causing only slight losses. Ex- 

 posure of the blocks treated with the low contentration of preservative to 

 Poly poms vaporarius and BTL U-U resulted in an increase in the amount 

 of decay. 



Since the resultant salts of the Greensalt reaction should be similar 

 to those produced by Greensalt K, field trials of these materials would be 

 expected to give comparable results. Extended field tests of wood treated 

 with one pound of Greensalt K per cubic foot have been in progress for ten 

 years without a single failure having occurred in more than 40 specimens. 

 Specimens treated with Greensalt O have been tested in the field for only 



