maine agricultural experiment station. 53 



Leaf Blister Mite. 

 (Eriophyes pyri.) 



Nearly 20 per cent of the inquiries which reached the Depart- 

 ment of Entomology of the Maine Agricultural Experiment 

 Station from about the middle of July to the middle of August 

 concerned the work of the leaf blister mite on apple. For the 

 most part this work was not unnaturally mistaken by the people 

 collecting it for some fungus disease, as the blotches on the 

 leaves resemble somewhat the injury caused by leaf -spot fungi. 

 The mites themselves are so small that they are invisible to the 

 unaided eye, and although they can be seen as moving specks 

 with a good hand lens, it takes a microscope to give any real 

 idea of their appearance. 



They are not insects in the true sense of that term, but 

 belong to the same class of animals as the spiders. They are 

 whitish elongate little creatures about 1-125 inch in length and 

 live within the tissue of the leaf, developing their colonies there 

 within the blister or "gall" which the irritation of their presence 

 causes. In winter they seek the protection of the scales in the 

 leaf buds. 



They are, indeed, among the smallest animal forms which 

 attack our crops, but they frequently occur in such abundant 

 colonies that the damage they do to the leaf is very conspicuous 

 This injury may first be noticed in spring when it appears as 

 reddish or yellowish green raised spots or blisters on the leaves ; 

 but it is not until much later in the season that it attracts gen- 

 eral attention, and by this time the blister spots are brown, giving 

 the leaves a diseased appearance. If the attack is severe the 

 foliage is likely to fall prematurely and dropping of the fruit 

 sometimes results. 



There is no remedial measure applicable at the time of the 

 year when the damage is apparent and by winter the work as 

 well as the mite being out of sight, the trouble is likely also to 

 be out of the mind of the orchardist. 



The leaf blister mite, however, yields readily to treatment 

 either by miscible oils and home-made oil emulsions or lime- 

 sulphur. Trees sprayed with lime-sulphur for other purposes 

 do not need especial treatment for the blister mite. When this 

 remedy is applied for the blister mite alone a dilution of one 



