ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



19 



sprays. Summer treatment is necessary for the common red spider, 

 since this mite is not on the trees when the earlier sprays are made 

 The treatment may be combined with that for the codling moth b\ 

 simply adding 1 to 1% gallons of a standard summer-oil emulsion to 

 100 gallons of the lead arsenate spray. Preferably this should be 

 done before July, unless previous applications of lime-sulphur solu- 

 tion make it inadvisable. Oil should not be used in summer sprays 

 less than 60 days after a lime-sulphur application, because of the dan- 

 ger of burning the foliage. 



Summer spraying for red spiders must be extremely thorough, as 

 the spiders infest the entire tree, and portions not sprayed often 

 harbor enough spiders to re- 

 infest the tree in a short time. 

 Oil sprays destroy only those 

 mites and eggs that are ac- 

 tually hit. The quantity of 

 webbing spun by the com- 

 mon red spider often makes 

 it very difficult to strike the 

 insect with" the spray, and 

 in such cases it is advisable 

 to use summer-strength lime- 

 sulphur, or wettable sulphur 

 at 3 to 5 pounds to 100 gal- 

 lons of water, or to dust the 

 trees with dusting sulphur. 

 The particles of sulphur lodge 

 in the webbing and the fumes 

 kill the mites running about 

 in it, including the young 

 as they hatch. Sulphur is 

 much less effective against 

 those species that do not 

 spin webs. 



PEAR LEAF BLISTER MITE 



The pear leaf blister mite 

 (Eriophyes pyri Pgst.) lives 

 in the buds, foliage, and fruit 



r i j x t+ Figure 20.— Adult clover mite. Forty- five times natural 



oi apple and pear trees. It size, 



produces small galls or blis- 

 ters on the leaves. At first these galls are greenish or reddish, 

 but later turn brown and cause dead areas. These areas may have 

 an appearance similar to that of apple scab but may always be iden 1 1- 

 fied by the small round hole which will be found on the under surface 

 of the leaf approximately in the center of each blister (fig. 21.) Since 

 the mites begin feeding "in the leaves before these are fully opened, the 

 new leaves show the blisters at once; and if the mites are numerous, 

 many of the leaves later dry and drop off. The fruit of the apple 

 is more seriously affected than that of the pear; it is attacked w hen 

 it is young, and the injuries cause mature fruit to be russeted or 

 deformed (fig. 22) and sometimes to crack open. The mites also 

 injure and deform the blossoms. There is some evidence that the 



