NEW APPLE LEAF" TROUBLES. 1 87 



such trouble occurred. For the past few years the)'- have been 

 cultivated, fertilized and pruned. 



The trouble appeared on the younger as well as the older 

 branches and is in no way connected with the normal yellowing 

 and falling of the inner and more shaded leaves which is of 

 common occurrence. Neither is it associated with any form of 

 spray injury for it occurs on sprayed and unsprayed trees 

 alike. However, leaves so affected are easily and sometimes 

 severely injured by lime-sulphur, used at a dilution which gave 

 absolutely no injurious effects on the healthy foliage of the 

 same tree. 



The leaves showing the chlorosis here described aie, as a 

 rule, variously spotted or mottled with irregular splashes of 

 yellow, giving a variegated appearance. No opportunity was 

 afforded to follow the course of the disease through the season, 

 but it is thought that the yellowing is progressive, eventually 

 involving a large part if not the whole of the leaf, for some were 

 collected which showed but little of the original green remaining. 



Figures 26 and 27 illustrate the appearance of the affected 

 leaves much better than any written description. The portion 

 of the young branch represented in Figure 26 gives an idea of 

 the characteristic appearance of the diseased foliage on the 

 tree. The leaves shown in Figure 27 were selected to show 

 individual variations. The two on the extreme left of this 

 illustration are far from typical of the great majority and repre- 

 sent about the only specimens of this character found, out of 

 probably more than one hundred collected. While the yellow- 

 ing appears to start frequently along the line of the larger leaf- 

 veins it is just as likely to> appear first in the tissues midway 

 between them. 



In the preliminary studies made in the field no definite clue 

 could be obtained as to the cause of the trouble. Conditions in 

 this part of the state during the growing season of 191 5 were 

 decidedly abnormal, being characterized by excessive rainfall, 

 associated with a large amount of cool, cloudy weather. The 

 following facts are against the unreserved acceptance of the 

 theory that weather conditions and the location of the orchard 

 were the prime contributing factors in bringing about the con- 

 dition observed. The disease was present the previous season ; 

 it occurred in the same locality on several varieties represented 



