Three Rust Diseases of the Apple 19 



CONTROL 



The control of apple rust by the eradication of the red cedar has 

 been successfully practiced since the pioneer work of Jones (1893) and 

 others. The similarities in the life histories of the three pathogenes, 

 together with observations in orchards, suggest that the problem is 

 essentially similar for the quince and hawthorn rusts. Considerable 

 progress has already been made in cedar eradication by growers in the 

 Hudson Valley, and a very considerable impetus will doubtless be 

 given to this movement by the heavy losses of the past two seasons, 

 not only on known susceptible varieties but on other varieties which 

 have heretofore been considered practically free from rust. However, 

 in a considerable number of cedar areas the cedar trees are in such 

 great preponderance over the apple trees, or are held in such high 

 esteem, that the method may still be considered impracticable. Com- 

 pulsory state-controlled eradication of cedars has been employed in 

 several cedar and apple area.s in the Hudson Valley, but it has been 

 attended by certain obvious difficulties. 



Clearly, the most satisfactory solution of the problem lies: in the 

 eradication of the red cedar for a distance of at least one-half mile 

 from apple trees, by individual growers or by neighbors in voluntary 

 cooperation. 



It has been stated that the apple and hawthorn rusts on cedars tend 

 to be localized near wild apple and hawthorn. In some cases the 

 removal of these plants from a cedar area would very markedly reduce 

 the amount of inoculum produced by the cedars. 



In areas where cedar eradication seems impracticable, the applica- 

 tion of fungicides is the most promising alternate control measure. 

 In two orchards, fruit of Mcintosh were inclosed in paper bags on 

 May 22, 1928, within a few days after the blossoming period (May 13 

 to 19). In each case the bagged fruits developed approximately the 

 same amount of infection as did uncovered fruits on the same and 

 adjacent trees. Thus, in 1928 at least most of the fruit infection on 

 Mcintosh was initiated before May 22 (about the time of the calyx 

 application). This suggests that the susceptible period of fruit, for 

 the quince rust, is passed in a relatively short time and during the 

 time when applications of fungicide for scab control are most needed. 

 In several orchards in which special attention was given to early spray- 

 ing or dusting for scab control, on Mcintosh particularly, the amount 

 of fruit infection (rust) was low in comparison with other varieties 

 and considering the exposure to sources of inoculum. In one instance 

 a definite comparison was possible between adjacent rows of two blocks 

 of Mcintosh trees similar in size and in other respects except in the 

 applications of fungicides. One block received four sprays (lime- 



