INTRODUCTION. 



In the fall of 190 1 the orchard of the Massachusetts Agricultural 

 College was discovered to be quite generally infested with the San 

 Jose scale. A careful examination was at once made and it was evi- 

 dent that this insect had been introduced on two Gano apple trees 

 purchased in the spring of 1896. In 1901 the trunks and larger 

 limbs of these trees were quite thoroughly encrusted with scales, 

 while the leaves and fruit were also covered to a less degree. 



The Orchard. 



The orchard is about 150 yards wide and 500 yards long, extend- 

 ing approximately in a northeast-southwest direction. The greater 

 portion is situated on a hillside sloping to the southeast and is pro- 

 tected on its northern and western sides by old growth forest. Dur- 

 ing the summer months the air currents usually appear to pass along 

 the orchard rather than across it. 



The trees are in five blocks, separated by driveways. Four of the 

 blocks are rectangular while the fifth is triangular and separated 

 from the northwestern side of the fourth by a road. The originally 

 infested trees were situated near the middle of the last row of the 

 first block, with only the width of the road between them and the 

 first row in the second block. 



The first block contains one row (the first, or northeast) of pear 

 trees. The remainder of the block is composed of apple trees which 

 have been set about five years and are just beginning to bear fruit. 

 In the second block, apples, cherries, peaches and plums are repre- 

 sented, all of bearing size, though young. The third block contains 

 large apple and cherry trees, some of them a foot in diameter at the 

 base, and a few small cherries recently set. The fourth block con- 

 tains few trees more than eight or ten years old while many are 



