EVALUATION OF WOOD PRESERVATIVES 139 



wood of western red cedar poles. It is relatively susceptible to creosote 

 and quite tolerant of pentachlorophenol in the block tests. Porta monti- 

 cola is relatively tolerant of pentachlorophenol and of copper compounds 

 under laboratory test conditions, and relatively susceptible to creosote. 

 It is of special interest also because it may be identical with some of 

 the fungi tested in Europe under the name of Porta vapor aria, and thus 

 its use may facilitate comparisons of a sort with results obtained by 

 other investigators. For instance, information has reached the Division 

 of Forest Pathology at Madison, from Findlay at the Princes Risborough 

 laboratory in England, that Harrow's Porta vaporaria^^ is the same as 

 Liese's,^^ and that it has been identified as a strain of Porta moniicola 

 by Miss M. Nobles of Canada. 



Within the last few years another fungus, characterized by the forma- 

 tion of conspicuous saffron 3^ellow strands, has been found associated 

 with decayed specimens of creosoted pine poles. ^ The writer has seen 

 the tell-tale strands in old cull dumps only. It has been identified as 

 Porta radiculosa. Whether it is truly a primary attacker or a secondary 

 organism is not yet clear. Soil-block tests are under way at Madison to 

 determine its significance as a possible species to supplement Lentinus 

 lepideus in the evaluation of creosote. 



In connection with the use of the three numbered ''standard" strains 

 listed above, there may always be some reasonable doubt as to whether 

 the cultures employed in different laboratories have the same virulence. 

 To answer this question precisely involves a lot of careful biological 

 check testing, and such tests are already being made in the Division 

 of Forest Pathology at the Plant Industry Station, Beltsville, Md. It is 

 assumed for the time being that the numbered strains are virulent and 

 satisfactory test organisms for such preservatives as creosotes and pen- 

 tachlorophenol-petroleum solutions. 



The Scope of the Soil-Block Evaluation Test 



For a complete understanding of the scope of the soil-block evaluation 

 test it is necessary to consider this test as having two functions. The 

 first function involves the use of the soil-block test per se (without 

 weathering) to measure the reaction of the test organisms to various 

 quantities of a given preservative, and to compare these reactions against 

 different preservatives. In this function the test has been used in lieu of 

 the agar Petri dish test,'' and is considered to be much more satisfactory 

 as a screening test by workers at the Laboratories. It has been employed 

 at Madison for testing the natural durabiUty of wood, plywood, fiber 

 board, etc. 



