326 Agkictjltukal Experiment Station, Ithaca, N. Y. 



Lintner reported it as excessively abundant in eastern New York in 

 1892. The disease is very common in pear orchai'ds near Ithaca, and 

 has very noticeably increased within the past three years. It doubtless 

 occurs in a majority of the pear orchards in the State. This completes 

 the recorded history of the disease in our own State and other States . 



These data indicate that the disease is of European origin. It had 

 become established in the United States in 1872, and had reached Aus- 

 tralia in 1881, and Canada in 1888. It is widely distributed over the north- 

 ern, eastern and southern portions of the United States, and has doubtless 

 been introduced into other sections on stockboughtin the east or in Europe. 



Its Destructive7iess. — The destruction wrought by the mite thus far 

 has not been very serious except in a few cases where it was excessively 

 abundant. The infested leaves fall from the trees sooner than the 

 others, thus depriving the tree of its breathing organs and materially 

 weakening it. Without its leaves the tree cannot store up the necessary 

 food in its winter buds to insure a healthy vigorous tree and a full crop 

 the next season. The freer from disease the leaves can be kept during 

 the summer and fall, the more vigorous will be the tree and the better 

 will be the quality and the greater the quantity of the fruit the next 

 season. Pear growers should therefore be on the watch for the Pear 

 Leaf Blister, and not let it get a foothold in their orchards. 



The Life History of the Mite. — According to German observers, 

 the exceedingly minute oval grayish eggs are laid by the females in the 

 spring within the galls that they have formed, and here the young are 

 hatched. How long they remain within the gall of their parent has 

 not been ascertained. But sooner or later they escape through the 

 opening in it, and seeking a healthy part of a leaf or more often crawl- 

 ing to the tenderer leaves of the new growth, they work their way into 

 the tissue and new galls are thus started. In this manner the galls on 

 a tree are often rapidly multiplied during tlie summer. The mites live 

 within the galls, feeding upon the plant cells, until the drying of the 

 leaves in autumn. They then leave the galls through the openings 

 and migrate to the winter buds at or near the ends of the twigs. Here 

 they work their way beneath the two or three outer scales of the buds 

 where they remain during the winter. Fifteen or twenty may often 

 be found under a single bud scale. In this position they are ready for 

 business in the spring as soon as growth begins; and they doubtless do 

 get to work earlj^, for their red galls are already conspicuous before the 

 leaves get unrolled.* 



* Mr. Crawford says : ' ' Tliere are two ways in which the mite survives the 

 winter wlien all the leaves are shed — first, by liibernating among the hairs of 

 and in the leaf bud, and, secondly, by forming colonies under the tender bark 

 of last year's growth, as I have found them in both situations." 



