54 BULLETIN 395, U. S. DEPARTMENT OF AGRICULTURE. 



plum curoiilio, since in the more important peach-producing sections 

 of the United States east of the Rocky Mountains any commercially 

 successful scab treatment must combine satisfactorily and econom- 

 ically with control measures for these associated troubles. 



THE TIME AND NUMBER OF APPLICATIONS FOR MIDSEASON VARIETIES. 



Treatment hefore the Uossoming period. — Numerous writers have 

 recommended as the first spray for scab a treatment just before the 

 blossoming period. Sturgis (1897, p. 271), apparently on a priori 

 grounds, suggested this treatment, while Selby (1904, p. 66) includes 

 it in his recommendations. His tabulated results (1898, p. 251-252), 

 however, show no decisive benefit resulting from this application, 

 while, on the other hand, his best control in certain cases occurred on 

 plats which did not receive this treatment. Evans (1911) and others 

 make like recommendations. Scott (1907, 1908, and 1909), Scott and 

 Ayres (1910), Scott and Quaintance (1911), and others showed that 

 scab can be successfully controlled when this winter apphcation is 

 omitted. Clinton and Britton (1911, p. 614; 1912, p. 374) concluded 

 from comparative experiments that this treatment had little or no 

 effect upon scab or rot. They (1912, p. 374) state — 



In 1910, all of the trees having this winter treatment gave just as high a percentage 

 of scab * * * as did those not having it, neither lot having any summer treatment. 

 In 1911, all the trees having this -winter treatment and three summer treatments did 

 not give any lower percentage either of scab or rot than those that received only the 

 three summer treatments. 



Furthermore, the writer's life-history studies previously reported 

 show that at the time of the winter treatment the fungus is so well 

 protected by the cuticle of the host that it would not be feasible to 

 combat it efficiently with any standard fungicide. It appears con- 

 clusive, therefore, that a winter application is not necessary for 

 efficient scab control. 



Treatment as calyces shed. — Chnton and Britton (1911, p. 614, 617) 

 recommend the application of a suitable fungicide at about the time 

 the calyces are shed. Their data (p. 614), however, do not show any 

 better results from this apphcation in conjunction with two later 

 treatments than from the later treatments alone, and these authors 

 (1912, p. 395) suggest that if any of these applications must be 

 omitted it should be the first. Blake and Farley (1911, p. 19) 

 reported that scab development was considerably checked, though 

 by no means controlled, by a single application of a suitable fungicide 

 when the calyces were being shed. They recommended (p. 26) 

 this treatment in conjunction with two later appUcations. They did 

 not, however, give a thorough test to the two later treatments alone, 

 using self -boiled lime-sulphur or a sulphur spray. Selby's (1898, p. 

 251) tabulated data, on the other hand, show no benefit from this 



