20!) 



15,000 and 159,000 bushels, the valuation ranginf^ from $21,000 to 

 •$1G6.000. 



The seriousness of rust in apple orchards is indicated by an cxanii- 

 nation made in 1922 of 50 orchards distributed among 25 counties. An 

 average of 58. G per cent of the leaves and 3 per cent of the fruits were 

 found diseased. Fruit infection was seen for the most part only in those 

 orchards where extremely severe leaf infections occurred. 



The fungus which causes apple rust is similar to the rust fungi of 

 cereals in that it depends for its propagation upon the presence of a second 

 host, which is, in this case, the common cedar (Juiiipcriis v'lrglniana L.). 

 On the cedar the fungus causes the well-known "cedar apple." Spores 

 borne upon these apples are transferred to near-by apple-trees on air 

 currents, and the infection of the apple is accomplished. 



There has been an attempt to secure the eradication of cedars in 

 certain parts of Illinois as a preventive measure in the control of apple 

 rust. On Map 45 is shown the distribution of cedar rust so far as it is 

 now known. A comparison of the distribution here shown with that of 

 the apple rust on Map 44, reveals a very striking correlation. 



Control of apple rust may be accomplished more or less successfully 

 by the api)lication of Bordeaux mixture and lead arsenate or by lime- 

 sulfur. More effective control can be had, however, by eradicating all 

 red cedars within one mile of the orchard. Where cedars are too abun- 

 dant for eradication, new orchards should include only resistant varieties, 

 among which are especially the Grimes and the Liveland Raspberry. 



Bl.\ck Rot 

 Caused by Physolospora cydoniac Arn. 



Black rot attacks the fruit, leaves, and twigs; but, as with blotch, the 

 greatest loss comes from the injury done to the fruit. 



Leaf infection, in the form of round spots, is commonly recognized 

 under the name of "frog-eye". Twig and limb cankers are compara- 

 tively rare, but when cankers on old limbs have enlarged sufficiently they 

 girdle the limb and bring about the death of all parts beyond them. The 

 entrance of the fungus into the apple is dependent upon the presence of 

 wounds — especially insect punctures. Besides the actual rotting of fruit, 

 diseased a]i])les drop early, and considerable rotting occurs in storage. 



The earliest record of the occurrence of this disease in Illinois is 

 1879, but the exact location is not known. The present known distri- 

 bution, as shown by the 1922 and 1923 survey, is indicated on Map 4(5. 

 The disease has been found in orchards in (!9 counties, and ranges in its 

 distri-bution from the northern to the .southern boundary of the state. 

 'I'here ajipear to be two general regions of occurrence: The first lies in 

 the southeastern part of the state in the Ohio, Wabash, and lower Missis- 

 sippi vallevs; the second appears to conform to the upper Mississip])i 

 Valley north of the junction of that river and the Illinois. Northward, 



