Muscardijve, a name given by the French to a disease which for the last 20 years has proved very destructive to silkworms, and has seriously interfered with the production of silk in France and other parts of Europe. The fact is now well established that the disease is due to a minute fungus, botrytis bassiana, which is not confined to the silkworm, but attacks several other caterpillars. The mycelium (see Fungi) of this fungus lives in and feeds upon the intestines and other interior portions of the silkworm, finally destroying it. After its death the reproductive portion of the fungus may be seen upon the surface of the worm, giving it the appearance of having been dusted with flour; under a microscope this appears to be a forest of minute branching threads which produce an abundance of spores. Sometimes the silkworm retains sufficient vitality to spin its cocoon, and the fungus does not manifest itself externally until the caterpillar has assumed the state of pupa. It is found that the disease is communicated even if the spores fall upon the skin of the worm; indeed, the spores are so exceedingly small that they readily escape observation, and when the fungus is once introduced into an establishment they may be on the leaves upon which the worm feeds, and be thus taken into its interior, or they may be brought in contact with the worms in various ways.
Absolute cleanliness and washing every portion of the room with lime water are the means of preventing its spread. Neither muscardine nor any other of the diseases of silkworms has appeared in California.