128 



.SIXTEENTH BIENNIAL REPORT 



all spores alighting on tlie bark will be 

 killed before tliey get in. It is evident 

 that tlie more tliorough the spraying, 

 the more perfectly the bark is covered, 

 the nearer the grower will get 100 per 

 Cent protection. 



It is an interesting fact that while 

 the tree is actively growing, the anthrac- 

 nose fungus can not get a start in the 

 bark. As soon, however, as the tree 

 goe'^ into dormancy at the close of the 

 season and active growth ceases, it can 

 no longer resist the invasion of the 

 fungus. That is why it is not necessary 

 to Protect the tree against disease in 

 the Summer, even though spores may 

 be formed at that time. Just as soon 

 as the fall comes, however, and rainy 

 weather with it, conditions are ideal for 

 infections. All through the fall and into 

 the Winter, infections may occur actively 

 and it is against this infection period 

 that 'the trees must be protected. To 

 insure complete protection, a spray ought 

 to be applied before the fall rains begin 

 and then again after harvesting to renew 

 the coating and insure continued protec- 

 tion through the rest of the winter. As 

 stated previously, growers object to the 

 early spray on bearing trees and are apt 

 to content themselves with the less per- 

 fect protection which the later spray 

 affords. As a result, anthracnose is 

 seldom reduced to a minimum, although 

 in ordinary seasons a reasonable degree 

 of control is secured from the late spray. 

 Growers must realize, nevertheless. that 

 preharvest rains in unprotected orchards 

 will mean a certain amount of infection 

 and after a fall season like that of 1920, 

 there should be no surprise if a consider- 

 able amount of infection develops where 

 only an after-harvest spray is given. 

 The Experiment Station is working on 

 the Problem of getting a more satisfac- 

 tory method of early protection than we 

 now have, but none of the half dozen 

 different materials and formulas tried 

 thus far appear to have any great ad- 

 vantage over a weak Bordeaux, and 



this spray admittedly has its drawbacks. The spray following harvest should be 



with the füll strength formula 6-6-50 Bordeaux. 



After the infection has taken place, it is some time before it becomes evident 



to the naked eye. Then it shows up in December or January as a small, round, 



APPLE TREE ANTHRACNOSE CAN- 

 KER — SEVERE DAMAGE, RESULT 

 PROM THE GIRDLING OF LARGE 

 LIMBS BY CONFLUENT CANKER. 



