ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



11 



On medium or heavy infestations of the San Jose scale, lubricating 

 oil emulsion or miscible oil must be used at a dilution containing 

 about 4 percent of oil, to obtain satisfactory results, although a 

 dilution containing 3 percent of oil is sufficient for very light infesta- 

 tions. This dilution allows about 2 or 3 percent of the scales to 

 survive, and these would result in a noticeable reinfestation during the 

 summer, unless very few scales were originally present. Lime-sulphur 

 solution must test at least 4/2° Baume for most infestations. This re- 

 quires 1 1 gallons of a concentrate testing 32° Baume to make 100 gallons 

 of spray. Very light infestations may be held in check with a dilution 

 testing at least 3%° Baume, requiring 8 gallons of 32° Baume concentrate 

 for 100 gallons. (For schedules of oil and lime-sulphur dilutions, 

 see pp. 68 and 69.) 



If the dormant- 

 season applications 

 have not proved ade- 

 quate, summer- 

 strength applications 

 of about 1 percent 

 oil emulsion, such 

 as are used for the 

 codling moth and red 

 spider, or of lime-sul- 

 phur concentrate (1 

 gallon to 50 gallons) 

 as employed for com- 

 bating the apple pow- 

 dery mildew, should 

 considerably reduce 

 the amount of fruit 

 spotted by the scale, if 

 applied during June 

 or August, when 

 most of the young 

 scales are present. 



OYSTER-SKELL SCALE 



The oyster-shell 

 scale (Lepidosaphes 

 ulmi L.) is found 

 throughout the Northwest, but occurs most commonly west of the 

 Cascade Mountains and is seldom seen in the irrigated valleys of the 

 interior. It is readily distinguishable from other scale insects by its 

 characteristic shape (fig. 10). The apple is a favorite food plant of 

 this scale, but it also lives on a great variety of fruit and shade trees, 

 ornamental shrubs and plants, and on native trees, such as willow 

 and dogwood. Its effect on the tree and fruit is similar to that of 

 the San Jose scale, and heavily encrusted trees or limbs may be killed. 



Figure 9.— Appls buds in proper condition for dormant spray. 



LIFE HISTORY 



If the old scales on the bark be turned over during the winter, they 

 will be found filled with small, pearly-white, oval eggs (fig. 11). 

 Often there are nearly 100 eggs beneath a single scale. These eggs 



