176 FRUIT INSECTS 



Remedial treatments. 



Orchardists should reject all nursery stock bearing many 

 oyster-shell scales. Nearly three fourths of the life of this pest 

 is spent as eggs well protected by the scale, and no thoroughly 

 successful method has yet been found for destroying these eggs 

 directly. Experiments indicate that fumigation with hydrocy- 

 anic acid gas, as practiced by nurserymen to kill the San Jose 

 scale, often does not kill more than two thirds of the eggs of the 

 oyster-shell scale. We have failed to kill many of the eggs even 

 with undiluted kerosene. 



The oyster-shell scale can be satisfactorily controlled, however, 

 by thorough applications of lime-sulfur as recommended for 

 the San Jose scale (p. 170). The lime-sulfur seems to loosen 

 the scales from the bark so that the eggs are either blown away 

 or fall a prey to their numerous enemies. This method is usually 

 adopted by commercial growers and is the most practicable 

 means of fighting this pest in large orchards. 



Effective work can also be done against the oyster-shell scale 

 in June, usually from the 1st to the 15th, when the young have 

 recently hatched and are crawling about or have just begun to 

 secrete a scale, by thorough spraying with a soap solution, 1 

 pound in 5 gallons of water, with " Black Leaf 40 " tobacco 

 extract, f of a pint in 100 gallons of water, adding 3 pounds of 

 soap to each 50 gallons, or with kerosene emulsion made accord- 

 ing to the standard formula and diluted with 6 parts of water. 

 In the South, where two broods develop annually, the young can 

 be killed with one of these sprays in August or September. 



The Scurfy Scale 



Chionaspis furfura Fitch 



For more than half a century this native American insect 

 has been one of the commonest and best known scales infesting 



