EXPERIMENT STATION BULLETINS. 



475 



With English Morello, however, the development of leaf-spot was very 

 pronounced on the check trees both years. In 1920 there was a serious 

 defoliation on the checks by July, probably half the leaves being lost. Early 

 in August the foliage was quite thin and by September the trees were entirely 

 defoliated. Considering the season as a whole, bordeaux ranked highest in 

 leaf -spot control but it caused the loss of many leaves as noted below. Lime- 

 sulphur ranked second and the two dusts a little lower than the lime-sulphur. 

 The control in the bordeaux plot was not perfect and the other plots showed 

 an increasing amount of leaf -spot in the order named above. There was 

 little difference between the two dusted plots but sulphur dust gave shghtly 

 better results than copper sulphate dust. 



In 1921 the Morello check trees did not show any serious development of 

 leaf -spot until August but by September these trees were practically defoliated. 

 The control of leaf-spot by all materials was almost perfect but there was a 

 difference in the effect upon the fruit and foliage as noted in the next para- 

 graph. The better results with the dusts in 1921 may be due to the fact that 

 the dusting was all done under favorable conditions. Other factors to be 





^ 



^^sr "->^ 



•hi"^s^ ^^ 







Fig. 23. — An English Morello tree from the bordeaux plot in 1920. All sprayed and dusted trees in 

 1921 were in even better condition than this at the end ol the season. 



considered are the different strengths of dusting materials and the weather 

 which was less favorable to leaf-spot development than in 1920. 



Effect upon foliage and fruit. Bordeaux in 1920 caused serious foliage 

 injury on Enghsh Morello and to a lesser degree on Montmorency. This 

 injury was of the yellow leaf type and caused quite heavy defoliation, 

 especially on the English Morello trees. This injury developed just after a 

 period of several days marked by dense fogs followed by high temperatures. 



