STATE POMOLOGICAL SOCIETY. 37 



favorable places and die, since their lodgment on apple foliage 

 is left entirely to chance. However, as all of you know, a 

 sufficient number of spores do lodge on apples to make it ex- 

 ceedingly unpleasant for us in certain years. 



Conditions Necessary for Infection. If one were to drive 

 through an orchard with a sprinkling cart about blossoming 

 time and wet the dead leaves on the ground, it would be per- 

 fectly possible to bring about the ejection of spores just 

 described. It does not follow, however, that scab spots would 

 develop on the foliage and fruit. It is absolutely necessary for 

 the germination of these spores and penetration of the cuticle 

 of leaf and fruit, that moisture be supplied in sufficient quan- 

 tity and for a sufficient length of time to permit the spores to 

 germinate. During periods of high temperature, germination 

 may occur in five or six hours, but during colder weather, i8 

 or 20 hours may be required. It will be seen, therefore, that 

 conditions favoring the ejection of spores are also essential for 

 spore germination. The ideal condition for abundant germina- 

 tion and infection would be a rain of sufficient extent to 

 moisten thoroughly the leaves on the ground, to eject the 

 spores from the perithecia, and this rain followed immediately 

 by calm, foggy weather. Every opportunity would be af- 

 forded for spore germination and abundant infection might be 

 predicted. 



Once the germ tube of the spore has punctured the cuticle, 

 there is no way possible of preventing further growth by tnc 

 application of spray substances that might be used safely on 

 apple foliage. It should be borne in mind that the spore is 

 exceedingly small and that the germ tube issuing therefrom 

 is also very small. From day to day food substance is ab- 

 sorbed from beneath the cuticle and a gradual development 

 occurs. In the course of a week or ten days the development 

 has reached such a point that one can see small olive green 

 .spots on leaf and fruit. 



Secondary Infection. Almost as soon as these spots are 

 visible to the naked eye, microscopic examination will show 

 that a new kind of spore is being developed. These do not 

 differ materially from the spores already described, but their 

 position and abundant production makes rapid and wide dis- 

 semination very easy. 



