INSECTS AFFECTING OHIO SHADE TREES 173 



The observations and practical spraying experience herein 

 recorded, in addition to the information compiled from the writings 

 of others, are mainly the result of work done by the Ohio Experiment 

 Station, in co-operation with the Department of Forestry of the City 



of Cleveland. 



SCALE INSECTS. 



Scale insects are among- the most formidable of the pests from 

 which the shade trees must be protected. On account of small size 

 and protective coloration they frequently escape detection by the 

 untrained eye until they have secured such a strong- foothold that 

 the host is permanently injured. Further, in addition to the ad- 

 vantage they possess by reason of the insidious nature of their 

 attack, some are extremely resistant to remedial measures, among 

 these being- some of our most common species, such as oyster 

 shell bark-louse, terrapin scale of the maple, etc. 



The majority of the species remain fixed after the scale cover- 

 ing is formed. The spreading is effected by the young as they 

 crawl about seeking a suitable place to begin feeding; as they are 

 carried short distances by spider webs or winds; or possibly longer 

 distances upon the feet and feathers of birds. This motile period 

 in the history is of short duration, usually not longer than two or 

 three days. 



Insects of this order obtain their food by inserting their sharp, 

 hair-like beaks into the tissues of the plant and drawing out the 

 sap, hence applications of poisons are ineffective, and for all practical 

 purposes it may be said that control methods are confined to spray- 

 ing with contact insecticides during one or both of two seasons, the 

 latter depending upon the species. Some scales are more easily 

 destroyed by the action of a strong spray, used during the winter 

 months, while others are susceptible to treatment with a weak spray 

 applied during the summer months when the brood of young is ap- 

 pearing. The last named method, however, is useful only when the 

 entire brood of young appear within a few days, and when the host 

 is foliated sparsely enough to permit the spray to reach all parts of 

 the plant. 



In appearance this scale is dark brown 



1 he oyster-shell dark louse* . * .,., , in _, 



Lepidosaphes ulmi. m color ' sha P ed llke ^oyster shell, and 



is about one-eighth inch in length. 



(Plate 1, Figs. 1, 2 and 3.) The winter is passed in the egg stage 

 under the protection of the covering scale, the large quantity of 

 whitish eggs being quite easily detected if the covering is removed. 

 The eggs hatch during the latter part of May or earlv June, at which 

 time the tiny, yellowish, mite-like scale insects may be located 

 by the unaided eye, as they crawl about seeking a suitable place to 

 begin feeding. 



