EXPERIMENT STATION BULLETINS. 487 



. INTRODUCTION* 



Michigan is one of the great tomato-growing states. The Michigan 

 crop produced amounts to nearly a million dollars annually, is^worth'^™^ 

 Tomatoes are grown for ordinary market purposes, for can- ^n'nuaii?!^ 

 ning and for seed. The type of culture and the varieties 

 used vary with the utilization of the crop. The methods 

 u:ved in growing the crop influence the prevalence of this 

 disease to a great extent. For example, it is found that 

 where tomatoes are staked, the damage from leaf-spot is 

 greatly reduced. In general, seedlings are grown in green- 

 houses or cold frames and set by hand in the fields. This 

 method of procedure lends itself readily to control measures 

 which entirely prevent damage from the leaf-spot disease. 



THE IMrORTANCE OF THE LEAF-SPOT DISEASE. 



The leaf-spot disease of tomato, commonly called by grow- The leaf spot 

 ers "blight," caused a practical failure of the crop in many slrilous'""^'^ 

 localities in 1915, and for the preceding five years, has ma- '^{^^^l^^J^^ 

 terially shortened each growing season. This condition is 

 found in every state where tomatoes are grown commercially. 

 The consensus of opinion of pathologists from all parts of the 

 United States, is that the Septoria leaf-spot is the most 

 serious disease of the tomato. 



The disease has been found in the northern, as well as the The disease 

 southern parts of Michigan. Its distribution is probably as spread'as'to- 

 great as tomato culture. mato culture. 



HOW TO TELL THE DISEASE. 



The signs of the leaf-spot disease are well expressed by the Leaf spot 

 common name "blight." The growers notice a general un- bughting of^ ^ 

 thriftiness in the plants along with a blight which begins on Jrom^^fhe^ 

 the lower leaves and which gradually advances ui)ward on bottom 

 the plant. (Fig. 2.) Blighted leaves if carefully examined 

 are seen to be covered with small circular spots, commonly 

 less than % of an inch in diameter. In some cases a whole 

 leaflet may be involved. These spots are sometimes black, 

 but are usually grayish with a black border. (Frontispiece.) 

 As the disease progresses the spots dry and the leaflets turn 



♦This popular bulletin is based on Technical Bulletin 25 of this Station. Anyone interested 

 in the more detailed account may secure the technical bulletin so long as the supply lasts. 



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