197 



Very little loss has ever been attributed to this disease. In 1919, a 

 year when the rust seems to have been unusually abundant, only a trace 

 of loss was reported. The disease is apparently limited in distribution, 

 being confined for the most part to the northern section of the state, 

 and even there it is seldom abundant. No satisfactory method of con- 

 trol is known, and it is doubtful whether one is needed with a disease 

 of such slight importance. 



Rosen's Disease 

 Caused by Pscudomonas dissohcns Rosen 



This bacterial disease is characterized by the rotting of the basal 

 internode of the stalk. As the rotting progresses, the stalk becomes 

 weakened in spots and leans sidewise. The progress of the rot is such 

 that a continual leaning of the stalk results in further twisting, so that 

 by the time the stalk is down the remaining fibers of the diseased inter- 

 node may be twisted as much as two and a half complete turns. 



It was found in Illinois in 1921 in two counties, Jackson and Ran- 

 dolph, where it was reported as serious in the fields affected by it. In 

 1922 it was again found in small amounts in a single field in Union 

 county, where it was reported to be causing the death of 1 per cent of 

 the stalks. In 1923 it was seen in Alexander county, where an examina- 

 tion of 100 acres revealed two infected stalks. As indicated on Map 

 21, its distribution is limited to four adjacent counties in southwestern 

 Illinois. 



Rosen's disease of corn is not yet well known, and control methods 

 have not been worked out. 



Black-Bundle Disease 

 Caused by Cephalosporium acrcinoiiiiini Cda. 



The black-Ijundle disease of corn has not been commonly recognized 

 in Illinois. It appears, however, to be an important disease. 



Its ajipearance in the field is recognizable from the fact that the 

 affected stalk takes on a striking red color. As the disease progresses, 

 the stalk begins to wilt at the top, the red color spreads do,wnward 

 throughout the stalk, and the entire stalk wilts and dies. A slashed stalk 

 shows the bundles to be discolored and blackened. 



The present known distribution of this disease is shown on Map 22. 

 Undoubtedly it is nuich more widely distributed. 



Its seriousness where seen, is indicated from an examination of 

 three fields comprising 9 acres in Champaign county. In one field 1 

 per cent of tJie stalks were diseased, and in each of the other two fields 

 2 per cent of tlic stalks. In Clark county an examination of 4 fields com- 

 prising 1.> acres showed 1 per cent, 2 per cent, 2 ])er cent, and 3 per 

 cent of the stalks diseased. The i)ercentage of infection is directly cor- 



