264 Journal of Agricultural Research voi. xiii, no. $ 



The records of the Plant Disease Survey of the United States Depart- 

 ment of Agriculture are as follows: 



No date. Michigan (R. H. Pettit).i 



Caused loss of thousands of dollars in the forcing houses. 

 1910. Ohio (A. D. Selby). 



Reported in one county. 

 1912. Oregon (H. S. Jackson). 



Limited. ' 



Utah (C. N. Jensen). 



15 per cent in some greenhouses. 

 1915. North Carolina (H. R. Fulton). 



Loss considerable. 

 Washington (F. D. Heald and D. C. George). 



Occurrence only. 



ECONOMIC IMPORTANCE OF ANTHRACNOSE 



The disease was stated by Selby (8) to be very important in 1895. 

 It is reported to have been quite prevalent in Ohio during that year and 

 to have caused considerable losses to the lettuce growers. 



Appel and Laibach (j) reported a 50 to 60 per cent loss in the fields 

 about Brandenburg, Germany. 



Authoritative reports from growers in Grand Rapids in 1898 and a 

 few years following indicate that the disease was serious enough to cause 

 the loss of most of the crop in practically the entire acreage about Grand 

 Rapids. Since that time the losses have been less uniform, and at the 

 present time only occasional greenhouses show serious outbreaks of the 

 disease. Careful search in almost any greenhouse will reveal occasional 

 plants, but few epidemic outbursts of the disease are now reported. 



A plausible explanation of this decrease in the amount of disease is 

 given under the discussion of dissemination of the fungus. 



SYMPTOMS OF THE DISEASE 



The general effect on the plant in this anthracnose is to produce a 

 general dwarfing and discoloration (see PI. C). Beds with affected plants 

 have a brown or yellowish appearance. In the field the disease in a moist 

 season may lead to death of the outer leaves. Since the attack is pro- 

 gressive, passing from older to younger inner leaves, the effect is to make 

 plants small and of second grade, if not indeed a total loss. The fungus 

 is found on the leaf blades and on the midribs. 



On the leaf. — The fungus produces a characteristic spot on the leaves 

 of affected lettuce plants. The diseased areas show first as small, pin- 

 point, water-soaked spots. These rapidly enlarge, and soon a straw- 

 colored spot 3 to 4 mm. in diameter is produced (PI. 20, A). The spot 

 is either circular or angular, depending on the proximity of large veins. 



1 February, 1906 (from records of the Michigan Experiment Station). At this time research by Prof. 

 Pettit and Mr. Moses Craig resulted in recommendations of subirrigation as means of water supply, 

 together with surface applications of sand. No publication was made of work done. 



