12 



CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



hatch shortly after the apple trees bloom, and the minute, whitish 

 young crawl out and settle in a few hours on some living part of the 



plant. They develop slowly, 



increasing the size of the 

 scale coverings as they grow, 

 until, in the case of the 

 females, the scales are about 

 one eighth inch long when 

 completed, dark brownish 

 gray, and shaped somewhat 

 like oyster shells. The male 

 scales are smaller and oval, 

 and the mature males emerge 

 from the scales with fully 

 developed wings. The fe- 

 male insects, on the other 

 hand, remain beneath the 

 scale coverings throughout 

 their lives, depositing eggs 

 under the shells in the fall 

 before they die. There is 

 apparently only one genera- 

 tion a year in the Pacific 

 Northwest. 



CONTROL 



The dormant-season ap- 

 plication of lime-sulphur 

 solution is not so effective 

 against the oyster-shell scale 

 as against the San Jose scale. 

 However, the regular annual 

 use of the solution keeps 

 the insects fairly well in 

 check. Oil emulsions or 



Figure 10 — Twig encrusted with the oyster-shell scale. 

 Four times natural size. 



miscible oils, at the dilutions recommended for dormant spraying 

 (p. 69), are more effective and should be used for severe infestations. 



COTTONY MAPLE SCALE 



The cottony maple scale (Pulvinaria vitis L.) 

 sometimes becomes quite common on Winter 

 Nelis and Anjou pear trees, but does not seem 

 to thrive on the Bartlett variety, and is very 

 seldom seen on apple trees. It is primarily a 

 pest of maple trees (fig. 12), as its name indi- 

 cates, and also lives on grape, boxelder, black- 

 berry, and a variety of other plants. It is a 

 native of Europe, and came to the United States 

 over 100 years ago. The insect is easily rec- 

 ognized by the cottony egg sac which the female 

 produces in the early summer, and which often remains for some time 

 About 3,000 eggs are laid in this sac and hatch during June and July 



Figure 11. —Inverted 

 scales showing eggs of 

 the oyster shell scale. 

 Nine times natural size. 



