TOMATO DISEASES 



407 



TOMATO DISEASES. Of late years Tomatoes have been extensively 

 destroyed by several virulent forms of disease. The first to attract 

 attention was a disease of the leaves in which these organs became 

 entirely enveloped in a dense pearly white or pinkish mass of powder 

 or mould. In bad cases of this disease the leaves are twisted, thickened 

 and distorted ; they next quickly rot and fall off, so that the Tomato 

 plants are ruined. When this mildew for such it is is examined 

 under the microscope and magnified 300 diameters, it is seen as 

 in the accompanying illustration, one vast mass of thickly com- 

 pacted, transparent fungus threads with an infinite number of pale 

 rose-coloured spores : the spores are often jointed, and so break up 

 into two, three, or four pieces, and every piece germinates as shown 

 at A, B, C, D, and reproduces the fungus. The spore production is so 

 profuse that in moderately bad 

 cases the spores may be seen 

 dispersed in the air like a vapour 

 or mist when the leaves are 

 touched. The spores germinate 

 not only on the Tomato plants 

 but in the air, on the glass and 

 on the shelves,, pots, &c., which 

 go to furnish a greenhouse. The 

 name of the fungus is Dactylium 

 roseum, and it has been de- 

 scribed as a distinct species or 

 variety under the name of D. 

 lycopersid. 



Another too familiar disease of Tomatoes is popularly known as 

 ' Black Spot.' This disease is also caused by a fungus, much smaller 

 in size than Dactylium roseum, and named Cladosporium lycopersid. 

 The peculiar habit of this fungus is to first attack the pistil of the 

 very young fruit ; when once the minute pistil is destroyed, as at A, 

 the fungus radiates from this point as a centre and gradually invades 

 the substance round the pistil in circles, one circle beyond another, 

 as seen in the illustration : the dead part of the Tomato now becomes 

 jet black and quite flat as shown. The black stain is not confined to 

 the exterior, it spreads deeply into the interior and turns the sub- 

 stance of the fruit into a putrid but generally firm and sometimes 

 hard mass. As with the Dactylium of the leaves, the fungus spreads 

 from one plant to another with great rapidity, but the growth is never 

 profuse with the Cladosporium ; although the fungus is sparingly 



THE LEAF DISEASE OF TOMATOES 

 Dactylium roseum, var. 

 (enlarged 300 diameters) 



