154 ANNUAL EEPOETS OF DEPARTMENT OF AGRICULTURE. 



packing, handling, and ventilation have been found to reduce the 

 losses to a minimum. 



APPLE BLOTCH, SCALD, AND POWDERY MILDEW. 



Observations on the distribution of apple blotch have shown it to 

 be more widely prevalent than is usually supposed. On the other 

 hand, in sections in which it was formerly very destructive, its de- 

 structiveness has been greatly decreased hj spraying. Proper spray- 

 ing through a term of years has practically eradicated the disease 

 from orchards in which 10 years ago it was known to be very de- 

 structive. 



It has been found that scald can be prevented by good aeration and 

 that the completeness of this aeration is of much greater importance 

 than its continuity. It is essential that the air movement be sufficient 

 to break up the layers of stagnant air around the apples themselves. 

 It has been found that in commercial storage scald can be prevented 

 much more readily with apples packed in boxes or ventilated barrels 

 than with those packed in tight barrels. It has been proved that 

 scald is not due to an accumulation of carbon diosid but to the pres- 

 ence of some other gaseous product of the apple. 



The growing seriousness of powdery mildew has caused great con- 

 cern among the apple growers in some of the irrigated sections of the 

 Northwest. It has been found that complete control can be secured 

 by the application of sulphur sprays early in the year. 



WHITE-PINE BLISTER RUST. 



It has been shown experimentally that the white-pine blister rust 

 overwinters on currants. Successful inoculations on black currants 

 were obtained with uredospores from currant leaves which had 

 remained in a natural state in the open throughout the winter: also 

 with spores from dry leaves which had been kept in the laboratory 

 through the winter. These results confirm the wisdom of the quar- 

 antine against currants. 



The rust on currants in Colorado and adjacent States, at first 

 believed to be the wdiite-pine blister rust, has been shown to be a 

 relatively harmless native rust with its alternate stage on the pinon 

 pine. This discovery has completely cleared up the situation in the 

 ■far West with respect to blister rust, showing, with other results, 

 that the far West is free from the true blister rust. 



The situation regarding this disease may be summarized as fol- 

 lows: 



(1) In New England and eastern New York the blister rust is 

 generally distributed upon currants and is beyond hope of general 

 eradication. It is being controlled locally by the destruction of the 

 alternate host of the disease. Experiments are under way in defi- 

 nitely chosen areas to determine the cheapest and most efficient way 

 of doing this. 



(2) In New Jersey and Pennsylvania the disease is under control, 

 having been eradicated in eight places. In New Jersey the disease 

 has not been found this season. In Pennsylvania it has been found 

 and eradicated in one place. 



