The CoUonj- Maple Scale. 249 



Still another enemy of this insect, and a very effective one at 

 times, is the predaceous caterpillar of Ijiietiliii coccidivora Co'nst. it 

 is said lo have been instrumental in keeping the cottony cushion scale 

 within bounds at Washington for a period of nineteen years. 



The statement is commonly made by entomologists that this 

 pest is not injurious for two consecutive years, the natural aiicniiv??. 

 •of the scale i)laying their part in keeping the forces of nature balanced. 

 But when, as often happens, nature introduces certain factors which 

 prevent the increase of parasites from surpassing that of the scale, 

 the equilibrium is lost, the scale gains the ascendency, and an ab- 

 normal state of affairs exists. It is in just such an overbalanced condi- 

 tion of things that recourse must bo had to artificial remedies. 



There are two stages in the life history of the scale during which 

 •spraying is practicable; i^umiiier .spraying, when the insects have just 

 hatched and are actively moving about, and wi'itcr spraying, after 

 they have become dormant and the trees have shed their leaves. 



In applying insecticides to infested trees the greatest precautions 

 should be taken not to destroy the natural enemies of the scale. 

 To quote again from Mr. J. G; Sanders,* "Hundreds of larvae Myper- 

 aspis Mnotata were found to have been destroyed by a summer 

 treatment with kerosene emulsion for the cottony maple scale in parks 

 of Chicago, and no doubt thousands of the minute chalcids were 

 Itilled, as they were found quite plentifully on unsprayed trees." For 

 this reason, as well as that of economy, rapidity, ease, and most of 

 all, effectiveness, the writer would advocate the winter treatment 

 "With kerosene emulsion. 



In response to frequent complaints from Broken Bow during 

 the winter of 1905-6, in regard to this pest, the writer was detailed 

 "by Prof. Bruner to take charge of some spraying at that place. 

 Unfortunately, however, it was not until April that he was enabled 

 to begin operations, the annoying delay being caused by the failure 

 •of the equipment to arrive at the proper time, and by the inclement 

 weather. At this late date the box-elders had begun to put out buds, 

 so that it was feared that injury might result to the trees by the use 

 of very strong emulsion, thus making the remedy worse than the 

 ■disease. Consequently they were treated with solutions containing IS 

 and 2 per cent kerosene. As soon as the leaf buds opened the 

 spraying operations were stopped, an emulsion weak enough to be 

 harmless to the trees having no effect whatever upon the wax-covered 

 •scales. Although this treatment was not as effectual as it might have 



'Bulletin 22. New Series, U. S. D3;;t. Agric, Div. Ent.. p. 13. 



