112 



A New Tomato Disease. 



[may 



last year, and growers are cautioned to be on the lookout 

 for this pest, which, if neglected, may become one of the 

 most serious sources of injury to the crop.* 



The fungus which causes the disease is closely related to 

 the " leaf spot " disease on strawberries, apples, pears and 

 chrysanthemums, but is quite distinct from any of these 

 diseases and it has been proved that spores of the fungi 

 causing " leaf spot " on the plants named above are incap- 

 able of producing this particular disease on tomatoes. In 

 the same way, experiments made with the object of 

 infecting potatoes and other plants with spores from this 

 tomato fungus have not resulted in any injury. Spegazzini 

 gave it a distinctive name, i.e., Septoria Lycopersici [Fungi 

 Argentini, Preg. iv. n. 289), but in the opinion of other 

 mycologists it ought to be termed Septoria Lycopersici var. 

 europaea, Briosi et Cavara. 



The tomato plants attacked show small blackish-green 

 spots on the leaves. These are irregular in shape at first, 

 but soon become concentric and finally confluent, and the 

 leaves, which are rapidly killed, roll up and hang loosely from 

 the stem. The fungus also attacks the stem, the calyx and 

 finally the fruit itself. When no remedial measures are taken 

 the whole plant may be destroyed within seven days from 

 the first sign of the disease. 



The spores of the fungus germinate during June and July, 

 the mycelium pierces the surface of the leaves and rapidly 

 branches in the interior. The injured portions quickly discolour 

 and small spots appear externally. The dead tissues, especially 

 in tomatoes grown indoors, dry up and exhibit spots of a some- 

 what dark brown colour, which appear hard and parchment-like. 

 In tomato plants cultivated out-doors the spots are softer and 

 black. When the dead portions of a leaf are examined by 

 means of a pocket lens one can easily detect numerous minute 

 black bodies not larger than the point of a needle all over 

 the surface of the leaf. At the same time one can distinguish 

 a light brown-coloured substance rising from the apex of 

 each small body like a curled, twisted thread. The manner 

 in which this substance rises from the bodies may serve as a 

 character to distinguish this disease from others. 



The disease has re-appeared this year, and precautions should be taken to 

 prevent its spread. 



