204 ILLINOIS STATE ACADEMY OF SCIENCE 



in many instances. For example, the 1922 survey in Oak 

 Park, Cook County, showed that fully fifty per cent of 

 the bushes eradicated in previous years had sprouted." 

 However, it is not likely that chemicals can be used con- 

 veniently on every planting because of the injurious ef- 

 fect on the soil, retarding plant growth one or two 

 years. 



Crushed rock salt has been applied to a number of 

 bushes in Jo Daviess County (Fig. 4). About ten pounds 

 is the recommended application for the average-sized 

 bush. It should be distributed over the crown. The bush 

 may be left standing or the top cut off before applying 

 the salt. The average cost per plant for treatment with 

 crushed rock salt was from five to fifteen cents, depend- 

 ing upon the character of the bush. This included the 

 cpst for salt and labor. 



RUST EPIDEMIOLOGY STUDIES 



In connection with the barberry eradication campaign 

 in Illinois numerous observations have been made in the 

 spread of black stem rust from infected barberries. Sev- 

 eral outstanding cases have been noted; one at Minooka, 

 Grundy County, probably is best known because it was 

 the first to be brought prominently to the attention of 

 farmers. It was discovered in 1919 and showed the re- 

 lationship so clearly that it was mapped and described 

 in the annual report of the barberry eradication cam- 

 paign of that year. 



Much of the rust around Minooka originated in a large 

 hedge of common barberry comprising some six hundred 

 bushes. Directly east of this hedge was a field of winter 

 wheat sheltered by an intervening orchard. This pro- 

 tection, together with the earlier development of winter 

 wheat, prevented serious damage to this field. About a 

 quarter of a mile southeast of the hedge was a field of 

 spring wheat with no protection other than distance. 

 Intervening was a pasture extending from the hedge to 

 the wheat. In this pasture was considerable wild barley. 

 Rust spread from the barberries to the grass and then 

 spread rapidly through the pasture to the grain where 

 it produced a 90 per cent infection. Directly across the 



