38 



BULLETIN 121, U. S. DEPARTMENT OF AGRICULTURE. 



extending into a private cucumber patch. On August 17 the course 

 of this drainage channel was found to be marked by new infection 

 in at least three rows and by a second old center. There was also 

 much scattered new infection in the region of the delta, both in field 

 3 and in the private patch as well. 



In field 4 the rows were parallel to the very slight western slope. 

 On August 18 a spread of even-aged secondary infection to the 

 westward from four of the six centers was noted. Examination of 

 the anthracnose centers in field 5 on August 18 showed a downhill 

 spread of infection across the rows in three instances. In two cases 





Fig. 13.— Diagram of field 2, Madison, Wis., August, 1916, showing the relation of surface drainage to the 

 distribution of anthracnose. The cucumber rows are indicated by broken lines and the slope by the 

 4-foot contour intervals. The four trapezoids represent water traps 1 to 4; the black circles and ellipses, 

 original centers of anthracnose; and the shaded areas, new infection noted on August 12. 



this infection extended across two rows downhill (14 feet), and at the 

 same time into the adjacent row above. 



Among the Madison fields that season, anthracnose became prev- 

 alent only where there were slopes. In field 19 on level muck soil, 

 there was very little spread from the old centers. In a large water- 

 melon field near Quitman, Ga., infection was found to be wide- 

 spread on certain slopes, but still restricted to small areas in the 

 more level parts. 



Late in the season of 1916 an excellent opportunity was afforded 

 in field 1 to observe the results of the heavy rainfall of the first week 



