6 BULLETIN 1162, U. S. DEPARTMENT OF AGRICULTURE. 



That the wind was an important factor in the spread of secidiospores 

 was suggested by the fact that oats growing on slopes inclined away 

 from the hedge were not infected, while oats on slopes inclined toward 

 the hedge were infected, even though they were a greater distance 

 from it. As the land in the vicinity of the hedge was rolling, checks 

 were made on the above observation, and in all cases the oats growing 

 in the fields sloping away from the hedge were less heavily infected 

 when a hill intervened between the hedge and the outward-facing 

 slope. The percentage of infection was heavier in those parts of the 

 adjoining oat fields which were most nearly on the same level as the 

 hedge than in intervening parts of the oat fields which were lower 

 than the hedge, even though the latter were closer to the source of 

 infection. This, again, suggests the wind as an agent in spreading 

 secidiospores. 



Pastures and fields of corn, alfalfa, clover, and barley (fig. 2) 

 separated the oat fields, yet these intervening fields did not prevent 

 the spread of secidiospores, as oat fields 170 rods distant from the 

 hedge were infected, even where no oat field intervened. The oats 

 on the side of the hill nearest the hedge in all cases showed the 

 heavier infection. A gradual decrease in infection occurred as the 

 distance from the hedge increased, with the exception of the outward- 

 facing slopes described above. 



The period from May 19 to 21, inclusive, during which abundant 

 aecidiospores were formed, was marked by a southwest wind of 48 

 miles per hour maximum velocity (Table 1). These data show that 

 wind may be an important factor in the greater percentage of 

 infection in that direction. 



Table 1. — Summary of the meteorological conditions occurring in the vicinity of Hinton, 

 Iowa, during the period from May 16 to 31, 1921. 

 [Relative humidities at 7 a. m. and 7 p. m. were averaged.] 





T 



2mperature (°F.; 



. 



Moisture. 



Wind. 





Extremes. 



Mean. 



Depar- 

 ture 

 from 

 nor- 

 mal. 



Mean 

 rela- 

 tive 

 hu- 

 miditv 

 (per 

 cent). 



Pre- 

 cipita- 

 tion 

 (in.)- 



Direc- 

 tion. 



Velocity 



(miles per 

 hour) . 





Maxi- 

 mum. 



Mini- 

 mum. 





Maxi- 

 mum. 



Aver- 

 age. 



1921. 

 May 16 



63 

 71 

 77 

 80 

 87 

 87 

 89 

 83 

 82 

 83 

 81 

 80 

 87 

 92 

 78 

 69 



42 



58 



58 



59 



64 



69. 



65 



69 



65 



64 



62 



61 



60 



70 



61 



56 



52 

 64 



68 

 70 

 76 

 78 

 77 

 76 

 74 

 74 

 72 

 70 

 74 

 81 

 70 

 62 



9 

 3 

 6 

 8 

 14 

 15 

 14 

 13 

 10 

 10 

 8 

 6 

 9 

 16 

 5 

 4 



59 

 78 

 82 

 80 

 61 

 63 

 61 

 69 

 79 

 76 

 77 

 70 

 63 

 48 

 83 

 81 



Trace. 



0.02 



.26 



.31 



" ".05" 



" ".63" 



.68 

 .79 



s 



S 



S 

 SW 

 SW 

 SW 



w 



N 

 NB 

 W 



N 



N 

 SE 



S 

 N 

 E 



SW 



25 

 27 

 25 



14.2 



May 17. 



12.7 



May l^ 



14.0 



May 19 



48 1 22. 1 



May 20 :.... 



32 1 18.1 



May 21 



32 

 29 

 12 

 25 

 25 



21.0 



Mav 22 



10.6 



May 23 



7. 4 



Mav 24. 



13.4 



Mav 25 



8.0 



May 26 



22 6.2 



Mav 27 



18 8.0 



May 28 



•'•.or 



17 8.2 



May 29 



29 | 12.2 



Mav 30 



21 13.0 



May 31 



18 | 10.1 



M 



82.2 



61.4 



71 



8.6 



70.6 









The weather conditions shown in Table 1, which prevailed during 

 the term when there was a major gecidiospore infection, were 



