222 



ease, diseased areas were found on an average of 31.-1 per cent of the 

 leaves, and the amount of infected fruit varied from 10 per cent to 45 per 

 cent. 



The fact that this disease is caused by a bacterium renders it difficuh 

 to control, and spraying seems to have little etTect. Cultivation and the 

 application of fertilizers, especially sodium nitrate, which tend to increase 

 the vigor of the trees, are etTective in holding it in check. 



Scab 

 Caused by Ckidosporhim carpophihtm Thuem. 



Scab of peaches, also known as "freckle," is a very common disease 

 in Illinois and is probably more disastrous in its effect than is usually 

 supposed. While attacking leaves and twigs to a certain extent, it is 

 primarily a disease of the fruit. Usually it appears on the exposed side 

 of the fruit and is often considered as a natural reaction to sunshine — 

 hence the name "freckle." Serious infection, however, results in mis- 

 shaped, unevenly ripened fruit. Cracks often appear which reach to the 

 stone of the peach. The fruit is thus rendered unsuitable for ready 

 marketing and is also made more liable to brown-rot injury and internal 

 breakdown. 



The early history of this disease in Illinois is not well known. The 

 earliest record of it is a specimen collected by F. S. Earle in Union county 

 in 1881. 



During 1922 and 1923 scab was found to occur in -Hi counties, the 

 distribution of which is shown on Map (58. It occurs most commonly in 

 the south quarter of the state. Occurrence northward is nuich more 

 scattered and irregular, and reaches only to Carroll and Ogle counties. 



The prevalence of scab is illustrated by an examination, in 1923, of 

 12 orchards, distributed among six counties. Infection was found on 

 8G.7 per cent of the trees and involved T9 per cent of the fruit produced 

 in the 12 orchards. The apparent damage caused by fruit infection varied 

 greatly in the several orchards and various expressions concerning its 

 frequency occurred in the notes as follows : great, 5 times : much, 3 

 times ; some, 2 times ; little, twice. Of the 88 acres reported on, great 

 damage was found on 54, much on ?, some on 23, and little on 4. In 

 reports showing much to great injury to the crop, mention is made re- 

 peatedly of the quantity of fruit cracked and deformed. Where injury 

 was less it consisted chiefly in a lesser degree of deformation and spotting 

 of the fruit which detracts from its appearance and makes it unsalable 

 as of the first class. 



Control of peach scab consists j^artly in the use of resistant varieties 

 and partly in the use of a well-apiilicd spray. Early Crawford.IIiley, 

 and Carmen are commonly thought to be most resistant, with Elberta, 

 Hale, and Belle of Georgia next. These varieties, however, may nut al- 

 ways be suitable to the needs of the grower, who nuist then depend upon 

 his' sprays for control. As infection begins when the petals have been 



