INSECT PESTS OF OHIO SHADE AND FOREST TREES 287 



Distribution. This insect occurs throughout Ohio, although it 

 is more prevalent in the vicinity of the larger cities than in the 

 rural districts. Outside Ohio it occurs in most sections of the 

 United States, the area of greatest destructiveness being the north- 

 ern part, particularly the northwestern. 



Natural enemies. The history of the activities of the oyster 

 shell bark louse in Ohio indicates that the insect is periodically 

 destructive, and that following each outbreak will ensue a period of 

 comparative inactivity. Thus it is clearly indicated that natural 

 control agencies play an important role in the insect's life economy. 

 An examination of the dead scales following the passage of the crest 

 of such an outbreak reveals the fact that many are pierced with 

 tiny holes indicating the escape of internal parasites. Of the known 

 internal parasites, the following may be named: Aphelinus dias- 

 pidis How., A. fuscipennis How., A. mytilaspidis Le B., A. abnormis 

 How., Aspidiotiphagus cirtinus Craw., Anaphes gracilis How. and 

 Cheiloneurus diaspidinarum How. 



A mite, Hemisar copies coccisugus, is known in France as a 

 predator upon the eggs of this scale. 



Ladybird beetles destroy considerable numbers of these insects, 

 and the following birds have been reported of value in this respect: 

 brown creeper, black-capped chickadee, titmice and the white- 

 breasted nuthatch. 



Control. Spraying with the sulphur sprays or with miscible 

 oil during the dormant period is the most satisfactory control 

 method to be used against this species under Ohio conditions. The 

 sulphur sprays should be used at the usual strengths, that is, 1 part 

 of the standard liquid lime-sulphur to 7 parts of water and the 

 proprietary powders at the strengths recommended by the manu- 

 facturers. The miscible oils should be used at the rate of 1 part 

 to 12 to 15 parts of water 



While these materials are the most effective known at this time, 

 yet as much as 3 years may be required to subdue the pest if the 

 attack is severe and the scales are piled one upon another, since the 

 oyster shell bark louse is one of the more resistant scales. 



Occasionally and particularly in years past it has been recom- 

 mended to make a summer application of kerosene emulsion at the 

 time the young appear, but this is not advisable due to the fact that 

 the brood does not appear simultaneously and because of the diff- 

 culty in covering every twig and branch of the host when the foliage 

 is out. 



