"SPOT" DISEASE.--Few managers of estates preparing pale crepe rubbers are unacquainted with this defect. It is manifested by the appearance of small coloured spots varying in density (_i.e._, number to a unit area) and differing in hue. The most common colours are black and orange, but "spots" of brick-red, yellow, violet and ruby and green tints have been noted, the last named very seldom. Sometimes in place of definite "spots," or colonies, the colour is spread over practically the whole surface of the rubber as a "flush."
These coloured spots, or "flushes," indicate infection by minute fungi, which are present in the latex prior to coagulation. The infection of the latex takes place in the field by means of spores, which are only visible with a microscope.
It is not feasible to discuss any method of preventing this infection of latex by air-borne spores, as the eventual preventive measures are so simple. But it may be believed that under ordinary weather conditions most latices are infected before reaching the factory. It is likewise true that even fine pale crepes shipped in perfect condition may contain possibilities of trouble in the form of "dormant" spores, the development of which may commence and continue if favourable conditions arise.
The subject of "'Spot' Diseases" has been treated fully in previous publications,[19] and it is not proposed here to enter into any lengthy discussion.
[19] "Preparation of Plantation Rubber," Sidney Morgan, 1913. "Spotting of Plantation Rubber," Keith Bancroft, 1913; Bulletin No. 16, F.M.S. Department of Agriculture. "Spotting of Prepared Plantation Rubber," A. Sharpies, 1914; Bulletin No. 19, F.M.S. Department of Agriculture.
If any reader is desirous of producing the defect experimentally, all that is necessary is to prepare a piece of crepe rubber of rather more than ordinary thickness, roll it up while wet, and place aside for some days.
This experiment reproduces the conditions favourable for the development of the spores, and spots of various colours may result. It will be clear that the chief factor influencing the result is the continued presence of plenty of moisture.
This condition may be created inadvertently in the course of factory practice, if piles of crepe rubber are allowed to remain for any appreciable period before hanging to dry. For this reason batches of wet crepe should always be placed on edge, to allow free drainage of surface moisture, if the rubber cannot be taken at once to the drying-sheds.