DISEASES OF CROPS 



201 



preceding fungi or to a number of others. Thorough spraying of the 

 orchards, careful handling of the fruit, regulation of temperature and 

 humidity will reduce these rots to a minimum. 



Scab (Venturia incequalsis [Cke.], Wint.). This is one of the most 

 injurious diseases of the apple. It causes a dry, black spotting of the 

 fruit which is well characterized by the name "scab." As the season 



advances the seriously 

 infected fruits become 

 distorted and cracked. 

 Affected fruits are es- 

 pecially susceptible to 

 storage rots. 



The disease also 

 attacks the leaves and 

 twigs, causing a more 

 or less thick, velvet- 

 like covering, varying 

 in color from olive- 

 green to black. 



Treatment. Spray 

 with concentrated lime- 

 sulphur (5 quarts in 50 

 gallons of water) or 

 Bordeaux mixture when 

 the pink shows, but 

 just before the blossom 

 opens. 



Blotch (Phyllosticta 

 solitaria, Ell. and Ev.). 

 This disease causes 

 dark, irregular blotches 

 on the fruit and, when 

 severe, causes a crack- 

 ing. In the older spots 

 a number of small, 

 black, fruiting dots are 

 formed. It also attacks the twigs, causing small tan-colored cankers. 

 In the old cankers the bark becomes cracked and roughened. 



Treatment. Spray with lime-sulphur or Bordeaux mixture. (See 

 table for apples, pears and quinces.) 



Rust (Gymnosporangium macropus, Link.). This disease attacks 

 foliage, fruit and twig, causing a yellowish orange-colored spot which 

 is not readily confused with other diseases. On the upper surface these 

 spots show numerous small yellow pustules becoming black. On the 



APPLE ScAB. 1 

 Photograph by Prof. M. A. Blake. 



'Courtesy of New Jersey Agricultural Station. 



