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A New Tomato Disease. 



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plants on finding suitable conditions for their development, 

 How easily the disease propagates and spreads will appear 

 from the following experiments : — 



Diseased portions of leaves were placed in a small bottle 

 with water and were well shaken. This water, which contained 

 an enormous number of spores, was used, on August nth, 

 to spray a healthy tomato plant, with the result that, on 

 August 16th, spots were noticed on the leaves and young 

 shoots of the plant. The whole foliage, stem and young fruits 

 were covered with spots by August 20th. Within five days from 

 spraying, ripe spores had formed in large numbers. Where 

 diseased leaves came into contact with healthy neighbouring 

 ones, these immediately contracted the disease. At first 

 it was possible to check the disease on adjacent plants by 

 removing the diseased leaves, but the plants soon became 

 so diseased that the cutting away of the leaves could no longer 

 be practised with any beneficial result. This observation tends 

 to prove that the spores are the main carriers of the disease. 

 Spores placed in water germinate readily after a few hours, 

 sending out a germinal tube from one and more of the divisions ; 

 they also germinate easily either on the surface of the leaf 

 or on the main stem and shoots. 



For the purpose of ascertaining the strength of a spray 

 necessary to combat the disease, three grades of Bordeaux 

 mixture were prepared, viz. : (a) 1 per cent., (b) 2 per cent, 

 and (c) 3 per cent, solutions. 



Infected material with numerous spores was placed in the 

 1 per cent, solution, and healthy plants immediately sprayed 

 after the spore , material had been immersed not longer than 

 one minute. A small ball diffuser was used, and the whole 

 process of spraying took no longer than about three minutes. 

 The same process was repeated with the remaining grades of 

 the solution. The results obtained were most striking. None 

 of the experimental plants took the disease, whilst plants 

 sprayed with the same spore material in water developed the 

 disease in. six days. One of these plants was sprayed imme- 

 diately after the appearance of the disease with a 3 per cent, 

 solution of Bordeaux mixture ; another was sprayed at a 

 later stage of disease, and a third at a still more advanced 

 stage. A 3 per cent, solution was used throughout, but the 



