54 



Journal of Agricultural Research 



Vol. VI, No. 1 



frequent intervals,^ and the average actual increase of spots per plant 

 computed (Table VIII and fig. 9). It was found that frorn 400 to i ,000 

 spots on a leaf, depending on its size, killed it within a few days. 



Fig. 9. — Curves of the 2-day average increases in the number of leaf spots per plant in a medium-early and 

 an early sugar-beet field, from June i8 to September 19, 1913, at Rocky Ford, Colo. 



Table VI. — Average infection cycle of Cercospora beiicola in a medium-early sugar-beet 

 field with poorly developed foliage and with a consequent low humidity early in the season 

 at Rocky Ford, Colo., in igij 



July 2. 



8. 

 10. 

 12. 



lA. 

 16. 

 21. 

 23. 

 25 

 2.~v 



Aug. I 



5 



9 

 II 



13 

 IS 

 18 

 22 



2S 



28 

 30 



Sept. 3 



6 

 8 

 10 

 13 

 IS 

 17 

 19 



Total 



number 



of 



leaves 

 marked. 



14. 2 



16.8 



17.4 



18. s 



19.7 



21-3 



22.6 



26.3 



27-5 



29 



30. S 



33 

 34 



35-5 

 36.5 

 37- S 



38. S 



40 

 41- S 

 43 



4S 

 46 

 48 



48. S 



SO 

 SO-S 

 Si-S 

 S2.5 



53 

 S3-S 



Total 

 num- 

 ber of 

 leaves 



in- 

 fected. 



5-8 



6 



6.6 



10.8 

 17.6 



27 



35- S 

 38 

 41 

 41 



41-5 

 42- S 

 42. S 

 44- S 

 44-5 

 44- S 



Total 

 num- 

 ber of 

 leaves 

 dead. 



4-3 

 4.6 



S-I 



s-s 



6.1 



8.9 



13 



13-5 

 IS- 5 

 IS-S 

 IS- 5 

 IS- 5 

 IS- 5 



15- S 



17 



23- S 

 25-5 

 26. 5 

 28.5 

 30 



32. S 



34- S 

 3S 



Num- 

 ber of 

 leaves 

 killed 

 by Cer- 

 cospora 

 beticola. 



Num- 

 ber of 

 infected 

 green 

 and 

 dying 

 leaves. 



4.4 

 4-7 

 4-S 

 4-3 

 4-3 

 4.1 

 4.4 

 4-7 

 4-4 

 6.3 

 10. 7 



18. s 



19- s 



20.5 

 20 

 20. 5 

 22. 5 

 24- 5 

 27 



29- S 

 28.5 

 25- S 

 23- S 



21- S 

 22. S 

 20.5 

 19 



17- s 



IS-S 



Number of func- 

 tional leaves — 



In- 

 fected. 



2.9 

 4.1 

 4.4 

 4-3 



4 

 4 



3-8 

 3-5 



18. s 

 17- S 



19. S 

 19 

 20 

 20.5 

 22. s 

 24- S 

 27 

 28 

 27- S 

 22.5 

 21.5 

 20.5 

 20.5 

 19 



16.5 

 15- S 

 IS 



Unin- 

 fected. 



8.9 

 8.7 

 9.6 



10. 6 



12.7 

 IS- 7 

 15-4 

 16.6 

 IS- 4 

 II. 7 



4-S 

 5-5 

 4-S 



Aver- 

 age 

 num- 

 ber of 

 leaf 

 spots 

 per leaf. 



1.6 



2-3 



2.4 

 2-4 



2-S 

 2-5 

 2-5 



3 



3-6 



3-9 



3-2 



3-9 



4-7 



15-3 



19. 1 



20. 6 



22. 2 



29. 6 



42.6 



51-3 



8s-9 



126. 6 



307. 8 



380.9 



485-1 



489 



S08.3 



479-2 



487.9 



504- S 



485- 9 



490.1 



' For convenience and uniformity, 2-day averages were used in making the comparisons, the coimts 

 being made usually at 2-day intervals. 



