46 FRUIT AND POTATO DISEASES 



liable to be attacked by this disease than others. Upon the 

 foliage the scab appears as black or dusky irregular patches 

 upon the upper surface of the leaf. The scab is caused by a 

 parasitic fungous plant, which finds its proper soil on the 

 fruit or leaf. The disease is spread by spores which develop 

 on the surface of the scab spots. 



The amount of damage done by the scab varies from year to 

 year. In some years it is very prevalent, while in others it 

 does comparatively little injury. 



The scab is one of the diseases which can be most effectually 

 prevented by spraying with a fungicide such as the Bordeaux 

 mixture. 



During the last three years the Baldwin apple, which is very 

 largely grown in southern New Hampshire, has been badly 

 affected by another fungous disease entirely different from the 

 scab. This disease is characterized by the appearance on the 

 surface of the apple of numerous small brown spots, varying in 

 diameter from a sixteenth to an eighth of an inch (see cover). 

 The spots are slightly sunken or depressed, so that the surface 

 lias a pitted appearance. They suggest the beginning of rot, 

 but they do not seem to increase in size ordinarily, thougli, 

 occasionally they do. They do not affect the tissues of the 

 apple deeply, and the principal damage done by the disease 

 seems to be the disfigurement of the fruit, which is often 

 great, rendering an otherwise perfect apple a second. 



The following experiments show the effect on this disease 

 of spraying with Bordeaux mixture. 



Experiment I. — Season of 1S95, on Baldwin apples: 



A plot of trees A was sprayed four times with i to 10 Bor- 

 deaux mixture (i to 8, i to 10, i to 12 Bordeaux mixture mean 

 that I pound of blue vitriol was used for every S, 10, or 12 gal- 

 lons of water), twice before blossoming, May 4 and 10, and 

 twice after blossoming, Ma}^ 28 and June 14. 



A plot of trees B was sprayed with i to 10 mixture once be- 

 fore, May 10, and twice after blossoming. May 28 and June 14. 



A plot of trees C was sprayed with i to 8 mixture three, 

 times. May 10, 28, and June 14. 



A plot of trees D was sprayed with i to 1 2 mixture three 

 times, May 11, 29, and June 15. 



