INSECTS AND THEIR CONTROL 243 



within the tissues of the leaf and injury is sometimes severe. 

 This injury is not confined to the foliage but also extends to 

 the fruit, causing scabbing and more or less distortion. 



The control of this species is best accomplished by a 

 thorough application of lime-sulfur as recommended for the 

 brown mite and citrus red-spider. Treatment should be 

 given just as the buds begin to swell in the spring. 



In addition to the pear blister-mite, several other species 

 are of economic importance. Two in particular should be 

 mentioned, the life histories of which are similar to that of 

 the pear-leaf blister-mite. These are the walnut blister-mite 

 which attacks both English and black walnuts, and the 

 grape-vine blister-mite which causes a condition commonly 

 known as erinose of the vine. The same treatment that is 

 necessary for the pear-mite will control these two species. 



Another species not commonly seen and by far the smallest 

 mite known, is the pear-leaf rust-mite, which commonly at- 

 tacks the foliage of the pear and which is recognized by a 

 rusty appearance of the infested leaves. Treatment with 

 sulfur in any form is all that is necessary to control this 

 species. 



355. Opportunities for insect study. Students frequently 

 have the idea that study must be confined to books. Nothing 

 could be further from the truth. Books help, most certainly, 

 but they never can take the place of observation at first hand. 

 In insects the student has a most fertile field for observation 

 and study. He will find everywhere an abundance of ma- 

 terial. He will be able to determine for himself such matters 

 as feeding habits, life histories, and economic control. He 

 should get assistance from books on insects, from his in- 

 structor and from experts in entomology. But it will not be 

 very long, if he observes closely, before he will begin to dis- 

 cover facts that no one else has noted. He will, in his own 

 small field, be ahead of the text-books. He will be among those 

 who are adding to the sum total of human knowledge. The 



