Insect and Disease Control 2G7 



dropping occurs, it is of course depleting to the vitality of 

 the tree. Its development on twigs is confined to the current 

 season's growth though the wounds thus produced may 

 persist as perennial cankers. 



Infections on the leaves first appear as small grayish 

 specks, somewhat angular in form, and later become various 

 shades of brown. Individual infections may run together. 



Infected areas appear on the twigs as black cankers in 

 early spring or more often not until May or June. The 

 first indication of infection is a minute spot having a water- 

 soaked appearance. As the spot enlarges, it elongates and 

 may extend half-way around the twig or even more. By 

 the second year these areas largely disappear but the cankers 

 carry the disease over winter and become sources of infec- 

 tion the next season. 



Infections on the fruit appear as a rule while the fruit 

 is still very small, as minute gray specks just beneath the 

 outer skin. As these areas develop the skin cracks slightly 

 and where infected areas are numerous the cracks run 

 together making a network of lines. Considerable difference 

 exists in the susceptibility of varieties. 



Methods of control of leaf-spot. 



Rolfs ^ found that bordeaux mixture would control the 

 disease but its use on peach leaves is prohibited by the 

 injury which it causes to them. Self-boiled lime-sulfur 

 mixture is less effective though its efficiency appears to be 

 increased by adding to it arsenate of lead at the rate of 2 

 pounds to 50 gallons. The poison probably controls in- 

 sects which might otherwise cause new infections. 



1 Memoir No. 8, Cornell Univ. Expt. Sta. "A Bacterial Disease 

 of Stone Fruits." 



