10 



CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



several hundred very small, louselike, yellowish, active young. These 

 young are capable of crawling considerable distances during the first 

 few hours of their lives, and spread about at that time. During their 

 period of activity they are often carried to other trees by the wind, 

 on the feet of birds, on the clothing of men working in the orchards, 

 or on horses or farm implements. They ordinarily settle down within 

 a few hours on the bark or on leaves or fruit, insert their long, thread- 

 like beaks into the plant tissue, and start feeding. Almost at once 

 they begin to secrete a waxy material which soon forms a character- 

 istic, circular, scalelike covering. The covering of the female when 

 fullgrown is about the size of a pinhead, grayish, with a dark, central, 

 nipplelike projection, while that of the male is somewhat elongated 

 (fig. 8). If these coverings are turned over, the delicate, bright-yellow, 



saclike bodies of the insects may be seen. 

 Growth is completed in about 6 weeks, 

 and there are two or more generations in 



a season. 



CONTROL 



Figure 8.— San Jose scale: Males and 

 females. Eight times natural size. 



Ordinary infestations may be con- 

 trolled by a single thorough application 

 of lubricating oil emulsion, miscible oil, 

 or lime-sulphur solution during the dor- 

 mant season. More than 1 year may 

 be required to bring very heavy infest- 

 ations under control, but this may be 

 accomplished by spraying the trees 

 twice in one season. If two applications 

 are made, one should be made in the fall, 

 if possible, and the other in the spring. 

 Not more than one application of oil 

 at dormant-season strength should be 

 made in a year, and if two applications 

 for the scale are contemplated, the first 

 should be of lime-sulphur solution. The 

 second may be either oil emulsion or lime-sulphur. 



The question of which material to use depends on what other 

 insects are on the trees at the time the spray is applied, and on the 

 kind of water available for spraying. Oil sprays are very effective 

 against the eggs of red spiders, tree hoppers, and the fruit tree leaf 

 roller, and against newly hatched aphids, and should be used if these 

 eggs or insects are numerous. Otherwise the lime-sulphur solution 

 is just as satisfactory. It is often desired to control the pear leaf 

 blister mite, on pear trees, and for this purpose lime-sulphur solution 

 is preferable (p. 68). Miscible oils may not always mix with certain 

 hard waters, but if thoroughly emulsified, they cause somewhat less 

 injury after the buds have begun to swell than do oil emulsions. 

 Lime-sulphur solution is perhaps safer for use during the delayed- 

 dormant period, although a sudden onset of warm weather following 

 its application will at times cause a dropping of the fruit buds. The 

 safest procedure is to use these materials only while the trees are still 

 dormant (fig. 9). The spray should preferably be applied after the 

 pruning is finished, as less material is required then, and the more 

 heavily infested limbs may often be removed before spraying. 



