Apr. 3. 1916 Climatic Conditions and Cercospora beticola 



55 



Table VII. — Average infection cycle of Cercospora beticola in an early sugar-beet field 

 in which there was a heavy production of foliage and a conseqtient high humidity 

 early in the season at Rocky Ford, Colo., in IQ13 



Date. 



Total 

 num- 

 ber of 

 leaves 

 marked 



Total 

 num- 

 ber of 

 leaves 



in- 

 fected. 



Total 

 num- 

 ber of 

 leaves 

 dead. 



Nimi- 

 ber of 

 leaves 

 kiUed 

 by Cer- 

 cospora 

 beticola. 



Num- 

 ber of 

 infected 

 green 

 and 

 dying 

 leaves. 



Number of func- 

 tional leaves — 



In- 

 fected. 



Unin- 

 fected. 



Total 

 number 

 func- 

 tional 

 leaves. 



Total 

 number 



of leaf 

 spots per 



plant. 



Aver- 

 age 

 num- 

 ber of 

 leaf- 

 spots 

 per 

 leaf. 



July 7- 

 9- 

 12. 

 14. 

 16. 

 21. 



23- 

 2S- 

 29. 



Aug. I 



5 

 7 

 9 

 II 

 13 

 15 



13-5 



14 



14-5 



II- S 

 13 



18.5 

 23 

 22 



22. 5 

 28 



26. s 

 26. s 



26.5 



24- S 

 23-5 

 23 



21. s 



22 



24- 5 

 25-5 

 24- 5 

 24- S 

 23- S 

 20. s 

 18 



10. s 

 10. 5 



5 



6 



S-5 



7 



8-5 



19- S 



20.5 



22 



22.5 



26 



26. s 



27- 5 



30 



29 



3°- 5 



30-5 



30 



30 



529 



596. S 



61S 



554-5 



574- S 



l>ii3-5 



2>2l6. 5 



3> 776- s 

 7.045.5 



1 1 , 966. 5 



12,638 



13.905 



14, 228. 5 



16,386 



16, 693 



14.993 



44 



49- 7 



51-2 



48-2 



44-2 



60. 3 



96-3 



171. 6 

 313- 1 

 427-3 

 476.9 



524- 7 

 536-9 

 668.8 

 710.3 

 651. S 



Table VIII. — Actual and 2-day average increase in the number of leaf spots per plant 

 in a medium,-early and an early sugar-beet field from June 18 to September ig, at 

 Rocky Ford, Colo., in igij 



The period of incubation of the fungus being from 11 to 13 days, as 

 shown by artificial infection experiments, a corresponding increase in the 

 number of spots on the leaves would not necessarily follow immedi- 

 ately after a period during which conditions favorable for infection pre- 

 vailed. 



Notwithstanding the early appearance of the spots in the medium- 

 early field — on June 20 — and a consequent expectation of an epidemic 

 of the disease, the increase in infection was very light (Table VIII) 



