ORCHARD INSECTS 



289 



but few scales in the spring may be covered by them in the 

 fall. Badly infested trees die in a year or two. All of our 

 common orchard trees are subject to attack. 



This pest may be controlled by spraying while the trees 

 are dormant. This will be more effective if they have been 

 pruned and headed in and the rough bark scraped from 

 the trunks and limbs. 

 Every scale must be 

 hit "to be killed, so 

 that every bit of the 

 tree must be thor- 

 oughly covered. 

 Lime-sulphur mixture 

 seems to be the best 

 spray, as it also de- 

 stroys various fun- 

 gous diseases and 

 some insects' eggs. 

 Miscible oils are also 

 used extensively and 

 have a certain advan- 

 tage on hairy apple 

 shoots and on badly 

 infested trees, as they 

 are more, penetrating. 

 They are used diluted 

 ten or twelve times 

 for winter spraying. Kerosene or crude oil emulsion, con- 

 taining 20 to 25 per cent of oil, is also satisfactorily used. 

 The best time to spray is just after the trees have dropped 

 their foliage in the fall and in the spring while the buds are 

 swelling, but before the foliage appears. No summer spray 

 has yet been tried which more than checks the development 



FIG. 207. The oyster-shell scale (Lepi- 

 dosaphes -ulmi Linn.). (After Howard.) 



a, female scales on twig; b, female scale from 

 above; c, same from below showing eggs; d, male 

 scale enlarged . 



