REPORT ON THE DISEASES OF SILKWORMS IN INDIA 77 



History of the disease and its causation. Being a disease 

 marked by very characteristic symptoms, grasserie has long been 

 known to sericulturists, and accounts of it are to be found in the 

 publications of the earlier writers on sericulture. Certain workers, 

 chiefly Bolle and Prowazek have tried to prove that a protozoan 

 parasite was the cause of this disease, but their work 

 has received no confirmation and is not generally accepted. It 

 seems evident that this disease is probably due to some metabolic 

 disturbance, and for this reason I have classified it along with 

 flacherie. Polyhedral bodies — the most characteristic symptom of 

 grasserie — are found in silkworms that have been attacked by the 

 fly parasite or that are suffering from some other disease common 

 to silkworms, such as flacherie or pebrine. If worms are carelessly 

 fed, especially if they are given mature leaf first and tender leaf 

 afterwards, or if after a period of dry weather showers of rain are 

 got, making the leaf very succulent and watery after being very 

 hard and dry — this factor can of course be of much importance 

 only in Bengal where the bush mulberry is cut down every bund 

 — if the respiration of the worms is interfered with in any way by 

 closing up the spiracles, if the air in the rearing room is damp 

 and cold and ventilation is defective, then it is said grasserie may 

 be expected. It is not, however, an infectious disease. 



Amount of disease in India. While grasserie is of absolutely 

 no importance in Europe it is quite a serious pest in India and in 

 the East generally. As will be seen from Appendix II, the rearers 

 in Bengal almost without exception complain of the ravages of 

 this disease. It is said to be important also in Madagascar, French 

 Indo- China and Japan. In India it occasionally assumes 1 grave 

 proportions and may cause heavy losses in a rearing. As grasserie 

 is a plague found only in caterpillars, it does not appear in our 

 census of cocoons. Further, in my tours in the silk districts I have 

 found only a few isolated cases, so that one might tend to look upon 

 it as relatively unimportant. This must not be done, however. 

 It is probably one of the important destructive factors in Indian 

 sericulture. Rearers estimate that they may lose as a rule 

 about I of their crop from this disease. 



What are the common causal factors ? We have noted 

 above that grasserie is not an infectious disease, but that it is caused 

 by unsuitable food or faulty ventilation. It is also a sequel of 

 certain other silkworm diseases. 



Methods of protecting worm froms disease. As grasserie 

 is the result of bad food or insufficient ventilation or some pre- 

 disposing disease, any improvement in rearing and the general care 

 -taken of the worms will help to prevent an outbreak. When the 



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