366 REPORT OF STATE BOARD OF HORTICULTURE, 



THE PEAR-LEAF MITE. 



By Prof. F. Ij. Washburn. 



The'aft'ection of the pear leaf is caused by a minute mite, Phytoptus pyri, 

 and is probably more common, and has been here longer, than most orchard- 

 ists realize ; in fact, it is very likely that much of that which has been 

 called "blight" on the pear by casual observers, is really the work of this 

 pest. The mite is very small, hardly visible to the naked eye, and is. well 

 represented'in the accompnying micro-photograph furnished by Mr. Pernot. 



It attacks both sides of the leaf, but individuals are morenumerous on the un- 

 der side where the small "blisters ' ' can be seen with the naked eye. A lens, 

 however, is required to show the opening in the center of the blister which 

 serves as a doorway for the mite. The location of the injury below is made 

 apparent on the upper surface of the leaf, by an irregular reddish spot, ( in 

 the early stages ) which changes later to brown and black, while the tissue of 

 the leaf between these two points, in which tissue eggs and young mites are 

 found, becomes corky and dies. 



The injury to the tree is more readily seen in the middle and late sum- 

 mer, when, iU'bad cases, almost its entire foliage looks blighted. 



The young mites when hatched spread from leaf to leaf, creating new 

 blisters and thus[^bringing about the condition referred to above. In the 

 autumn, when leaves begin to wither and fall, the mites migrate to the 

 twigs and hibernate beneath scales of bark or bud in the minute crevices on 

 twigs, and in the spring they are fully open. It is hardly necessary to say 

 that this^mite saps the vitality of the tree, and interferes with the natural 

 functions of the leaves. The work of this pest is illustrated by the accom- 

 panying full-page'plate, showing views of upper and lower surfaces of leaves. 



When a tree is observed to be first attacked pick off and burn the infected 

 leaves. Heavy pruning and burning the cuttings of such trees as are badly 

 affected, during the winter, will probably be more efficacious than anything 

 else. One[or two sprayings of kerosene emulsion in the antumn when mites 

 are migrating would destroy many. The same spray, used several times, 

 has been recommended for winter use. It is highly spoken of in a Cornell 

 University bulletin, and is to be used in this proportion : One part emulsion 

 to seven or eight parts of water. 



PS.— The best remedy for Oregon is siilphur.'lime, and ?alt before the buds swell, 

 followed by dusting witli sulphur when leaves have formed.— Hknhy E. Dosch. 



