174 OHIO EXPERIMENT STATION: BULLETIN 194 



A number of plants are' quite susceptible to this scale, the 

 most common for Ohio being 1 Carolina and Lombardy poplar, 

 willow, horse chestnut, ash, sassafras, and red-twigged dogwood. 

 The poplars are undoubtedly the most susceptible of all, and so in- 

 jurious in fact is this scale to these trees that the authorities in Cleve- 

 land have stopped the planting of them, and wherever practicable are 

 replacing growing trees with more desirable kinds. 



Spraying during the early spring with the lime-sulfur wash, or 

 during the hatching period with kerosene emulsion or whale oil soap 

 solution, is the remedy usually employed against this pest. How- 

 ever, for extensive spraying operations, the two latter materials are 

 hardly practicable, as in order to be effective they must be applied 

 during the interval between the hatching of the scale insect and the 

 completion of the first scale covering. This allows a few days only 

 an d therefore is prohibitive of work on a large scale. 



The lime-sulphur wash is undoubtedly the best of the control 

 methods to be used against this scale, but in the author's experience 

 it has proven spmewhat of a disappointment. From observations 

 made upon hundreds of trees and shrubs, sprayed with a mixture 

 made by experienced men and applied thoroughly, it is apparent that 

 only when conditions are the most favorable are the results follow- 

 ing its use satisfactory. A slight dampness, such as light fog, at 

 the time of application; a somewhat weakened spraying mixture; an 

 extra case of infection where several scales are piled upon one an- 

 other; a temperature below 32 degrees; any of these unfavorable 

 Conditions is sufficient to give poor results. 



In spraying trees that are deeply incrusted with the scale, the 

 mixture cannot be forced to penetrate underneath the outer layers 

 and frequently many escape, to multiply the ensuing year. 



Sassafras and soft maple, both well .infested with this species, 

 were carefully sprayed under favorable conditions during the spring 

 of 1907, with scalecide and limoid. This scalecide was used in a 5 

 percent solution, and the limoid was prepared after the following 

 formula: Limoid, 30 Ibs., kerosene, 7/^ gal., water to make 50 

 gallons. In every instance the scale increased abundantly 'during 

 the ensuing season, indicating that little benefit had resulted from 

 the treatment. 



Because of the power often possessed to withstand the action of 

 the most practicable of the stronger scale insecticides as a winter 

 treatment, and of the the impossibility of doing extensive work during 

 the summer period, the writer is almost ready to place the oyster 

 shell on a par for destructiveness with the San Jose species, when 

 it occurs under city conditions. 



