ORCHARD INSECTS OF THE PACIFIC NORTHWEST 21 



the San Jose scale; that is, a solution testing 4%° Baume (table 1, 

 p. 68). If the San Jose scale is not present, the solution need test 

 only 3K° Baume. Spraying should be completed in the spring before 

 the buds have started to open, for the mites get into the leaves soon 

 after that and can not be reached with the spray. Good control may 

 also be obtained by spraying in the fall, as soon as the leaves have 

 dropped. Oil emulsions are not very effective unless applied just as 

 the buds are swelling noticeably, and the weather must be warm at 

 the time in order to allow the oil to penetrate into the buds and kill 

 the mites. 



RUST MITE 



A very small mite, not unlike the pear leaf blister mite, is often 

 found on the under surfaces of apple and pear leaves as well as on 

 prune leaves. This is the rust mite (Phyllocoptes schlechtendali Nal.), 

 so named because its feeding usually produces a rusty appearance on 

 the leaves. It also causes the leaves to roll longitudinally. At times 

 the fruit also is attacked and may become russeted. The mite itself 

 is slightly smaller than the blister mite and can scarcely be seen with 

 the naked eye. Under a lens it is found to be somewhat shorter and 

 more triangular in shape than the blister mite. Instead of producing 

 blisters, this mite feeds on the leaf surface during the growing season 

 and hibernates in the buds. It may be controlled by the same means 

 used for the blister mite; and since it is exposed during the summer, 

 sulphur or oil sprays applied during that time will 

 also effect control if care is used to spray the under- 

 sides of the leaves very thoroughly. 



ROSY APPLE APHID 





rr,, , -i ' i / a 7 • -r>i\ Figure 23.— Adults of the 



I he rosy apple aphid (Anuraphis roseus Baker) pear leaf blister mite. 

 curls the leaves, particularly those on the fruit ££* times natural 

 spurs, and infests the young fruit, causing it to 

 become stunted and distorted (fig. 24). These " aphid apples" do 

 not thin out normally during the "June drop" and clusters of them 

 are often conspicuous in the fall, especially on the lower and inner 

 parts of the trees. At times they are sufficiently numerous to cause 

 a distinct reduction in the marketable crop. This aphid was prob- 

 ably introduced from Europe. It feeds only on apple and on its 

 alternate summer host, the plantain or ribgrass. 



LIFE HISTORY 



The aphid passes the winter in the egg stage on apple trees, and the 

 eggs hatch in the spring when the buds begin to swell appreciably^ 

 The young start feeding in the unfolding fruit buds, causing the leaves 

 to curl as they develop. Several generations are produced on the 

 apple and feed on the leaves and the fruit. Tightly curled leaves often 

 contain hundreds of the characteristically purplish or rosy-brown 

 aphids, and the species may be distinguished readily by its color and 

 by its habit of curling the leaves and deforming the fruit. As the 

 weather becomes warmer, brownish-green, winged individuals develop 

 and migrate to the plantain. Most of the aphids have left the apple 

 by early July. Migration to other apple trees does not occur, and 

 trees not bearing winter eggs remain free of infestation. On the 

 plantain several generations of yellowish-green aphids occur, and in 



