EXPERIMENT STATION BULLETINS. 



431 



was to be used for the "pre-pink" spraying experiment and leaves from this 

 orchard were collected daily and sent to Mr. Bennett who examined them to 

 determine the condition and degree of development of the scab spores. 

 Many spores w^ere mature by April 4, when the first leaves were collected and 

 by April 21 practically all were mature. The first spore discharge occurred 

 on April 21 but the blossom buds did not separate in the cluster until April 

 26. The temperature was comparatively high from April 2 to 7 inclusive 

 and the buds were forced into the "pre-pink" stage by this period of high 

 temperature. From April 8 to 19 the temperature was low and the ground 

 was covered with snow part of the time. The buds advanced very little dur- 

 ing this period but the temperature was again high from April 20 to 30 and 

 the buds developed rapidly. There were frequent rains during this period 

 and Mr. Bennett's studies show that most of the spores were discharged 



Fig. 1. — A cluster of blossom buds in a desirable 



stage of development for the "pre-pink" 



application. 



Fig. 2. — The pink or cluster stage, when apples should 



always be sprayed regardless of whether or not 



they have received a "pre-pink" application. 



between April 21 and 28. Trees in this orchard which did not receive the 

 pre-pink application were unprotected during the greater part of the first 

 period of spore discharge. 



The studies discussed in the foregoing paragraph refer only to the first or 

 primary discharge of spores from the old leaves and has no reference to the 

 later formation of a different type of spores on new leaves and fruit. 



Spraying experiments. The Maynard Duchess orchard, from which the 



