Circular No. 121. Issued April so, 1910. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



THE OYSTER-SHELL SCALE AND THE SCURFY SCALE. 



{Lepidosaphes ulmi L. and Chionaspis furfura Fitch.) 



By 



A. L. QuAiNTANCE, In Charge of Deciduous Fruit Insect Investigations, 



and 

 E. R. Sasscer, Scientific Assistant. 



INTRODUCTION. 



The oyster-shell scale (Lepidosaphes ulmi L.) and the scurfy scale 

 (Chionaspis furfura Fitch) are, with the exception of the San Jose 

 or Chinese scale (Aspidiotus perniciosus Comst.), more frequently the 

 subject of inquiry by orchardists than all other species of scale insects 

 combined. These two scale pests are now ver}' generally distributed 

 throughout the country, and from their relatively conspicuous appear- 

 ance are often detected by observant fruit growers who frequently 

 believe them to be the more serious San Jose scale-. The oyster-shell 

 and scurfy scales, while not dangerous in the sense of generally causing 

 the death of infested trees, are, however, of considerable economic 

 importance. The complete killing of individual branches of apple 

 trees by either species is a matter of frequent observation, and trees 

 so badly infested are frequentl}'' greatly stunted and retarded in their 

 growth, resulting perhaps in extreme cases in the death of the trees. 

 Of the two species considered, the oyster-shell scale has been and is 

 at the present time the more important. Its injuries to certain 

 shade trees, especialh'' poplar and maple, have been the cause of much 

 complaint during recent years. Such shade trees are ordinarily not 

 sprayed for scale insects, and the increase of these pests from year to 

 year is thus checked only by their natural enemies. The writers 

 have frequently seen maple and poplar trees literally incrusted from 

 top to bottom with the oyster-shell scale, many of the limbs killetl, 

 and in rarer instances the trees quite dead — without doubt owing to 

 the attack of this scale insect. 



[Cir. 121] 



(1) 



