479 



Malay States, so that the disease has little more than a passing in- 

 terest. It is, however, interesting to record its occurrence in this coun- 

 try, and a brief note will be given of the symptoms of the disease 

 and of some methods of treatment which are likely to prove effective. 



The disease is well-known in the United States of America where 

 it has been carefully studied by Dr- E. Smith on potato, tomato and 

 egg-plant {Solanum melongena). It has also been recorded on potato 

 in Scotland, in the north of England and in Mysore, and it has 

 recently been reported from Ceylon. 



The symptoms of the disease appear to be constant in the dif- 

 ferent countries in which it is known to occur, and they may be 

 briefly reviewed thus: 



Attacked plants show a wilting and shrivelling of the leaves ; 

 soon afterwards brown streaks appear on the stem and spread down- 

 wards to the parts underground. Finally, the whole stem rots. 

 A browning of the affected parts is very characteristic of the pre- 

 sence of the bacterium ; the browning will be fouiid to be first 

 evident in the vascular ring on examining the cut surface of an 

 affected stem. The vascular bundles are first affected, the suppl}' of 

 water to the leaves is checked and the consequent wilting and 

 shrivelling makes its appearance. 



The disease in the potato tubers is very well-marked by the pre- 

 sence of a circular, usually incomplete, brown ring which is situated at 

 some litttle distance from the surface and which corresponds in posi- 

 tion?with the vascular ring of the tuber. This ring darkens and 

 expands until the whole of the starch-producing area of the tuber 

 is affected. The tuber decays and the bacteria are liberated in the 

 soil where they can infect other healthy tubers. 



Dr. E. Smith considers that the rapid spi'ead of an epidemic is 

 due to insects of different kinds feeding alternately on healthy and 

 infected plants. Under these circumstances it is advisable to spray 

 the plants with an insecticide. A vegetal wash, e.g tobacco wash, 

 should yield good results. This may be made by infusing half a pound 

 of tobacco leaf in water for about six hours, straining oft' and press- 

 ing the tobacco and again infusing ; the extract is added to a solution 

 of half a pound of soft soap in water, the whole being made up to ten 

 gallons. The wash is applied by means of a spray. Any coarse 

 tobacco leaf may be used. 



Infected plants should be taken up along with their roots and 

 burnt. They must on no account be thrown on to a manure heap. 

 In the case of the potato plant it is advantageous to lift the crop early 

 when the disease has made its appearance; in this way many of the 

 tubers may be saved. 



Plants belonging to the potato family should not be planted on 

 soil which has yielded infected plants for at least two years, since 

 the bacterium probably attacks a large number of members of that 

 family {Solajiaceae). 



