78 PEAR GROWING IN CALIFORNIA. 



structive. Like many other borers it prefers trees that are weak, 

 dying or dead. Hibernation and breeding take place in piles of 

 orchard primings. 



Control. 



It is important, if this pest is trouble-some, to remove all dead wood 

 from the orchard and vicinity. 



MELON APHIS (Aphis gossypii). 



The melon aphis resembles very closely Aphis medicaginis. It works 

 on cotton, melons and many other plants, as well as the pear. On 

 the latter it becomes abundant during certain seasons, its injury being 

 exactly the same as that of the other species mentioned. 



Control. 



Use Formula No. 3. 



OYSTER-SHELL SCALE (Lepidosaphes ulmi). 



This scale, while rarely found in California, has been known to occur 

 on young pear trees. It is distinguished by a long, curved, shell-like 

 body. Like other scales, when unchecked it sometimes becomes so 

 abundant that a tree is practically covered with it. 



Control. 



Use Formula No. 1, 2, 5, 6 or 7. 



PEAR-LEAF BLISTER MITE (Eriophyes pyri). 



In the Sierra Nevada Foothill and Mountain Region of California 

 the blister mite is a serious pest, especially on younger pear trees. 

 Also pears of the Northern and Central California Interior Valley 

 Region are subject to the attack of this pest, but not to the same 

 extent as those in the previously mentioned region. The injury is 

 distinguished early in the season on the foliage by small reddish 





FIG. 169. Pear leaf blister mite. (After Nalepa from Parrott.) 



blister-like swellings which later turn black and dry up. An examina- 

 tion of these little blister-like patches will reveal the presence of a 

 little hole on the under surface of the leaf, by which the mites enter 

 and leave the blister. Hibernation takes place under bud scales. The 

 pest is almost microscopic in size and is rarely seen by the average 

 orchardists. The injury to fruit is sometimes severe and consists in 

 russeting and distortion. 



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