ANTHEAClSrOSE OF CUCURBITS. 



31 



conditions is not clear, unless the rains of July 12, 16, and 19 served 

 to render conspicuous the incipient centers already existent. 



We have then, on August 1, 20 centers in field 1 and 13 in field 2, 

 none of which were showing much secondary infection. The further 

 observation of anthracnose occurrence in fields 3, 4, and 5 was inter- 



Fig. 12.— Diagram showing the weather conditions at Madison, Wis., during the su m mer of 1916. The 

 curve represents the daily mean temperatures; the dotted line, the approximate optimum for the fungus; 

 the black columns, the rainfall. 



fered with by the removal of plants in connection with a mosaic con- 

 trol experiment. The data presented above, as well as results that 

 were obtained later on these fields, are summarized in Table III. 



Table III. — Anthracnose in fields at Madison, Wis., in 1916. 





Date 



first 



noted. 



Progress of disease. 



Field. 



Date. 



Number 



of 

 centers. 



Date. 



Number 



of 

 centers. 



Date. 



Number 



of 

 centers. 



No. 1 



July 19 

 July 20 

 July 21 

 July 22 

 ...do 



July 27 



...do 

 July 21 

 July 22 



...do .... 



15 

 5 

 1 

 1 

 1 

 1 



Aug. 3 

 Aug. 1 

 July 26 



20 

 13 

 5 



Aug. 15 

 Aug. 14 

 Aug. 11 

 Aug. 18 

 ...do 



46 



No. 2 



30 



No. 3 



12 



No. 4 



6 



No. 5 







10 



No. 19 



Aug. 24 



Aug. 24 







Aug. 30 



2 











The slowness of spread of the disease up to the first week in August 

 may be in part explained by the extremely hot, dry weather of July, 

 with no heavy rains after July 20. Reference to the weather chart 

 will show that the daily mean temperatures during the latter part of 

 July were well above the optimum (75° F.) for this fungus. Edger- 



