INSECT PESTS OF OHIO SHADE AND FOREST TREES 201 



Nicotine sulphate. — Tobacco decoctions and teas have long been 

 known and used as insecticides, but only within recent years have 

 they been produced on a commercial scale in the form of a stable, 

 constant product. This we now have in the highly concentrated 

 form of nicotine sulphate which is used as a contact spray on plants 

 in foliage more generally than any other material. Its greatest 

 single field of usefulness is for the destruction of plant hce and 

 similar pests. It is safe, is shipped in highly concentrated form, 

 ana is rarely disappointing when correctly used. 



For combating the average plant louse, use : 



Nicotine sulphate M pint 



Laundry or fish-oil soap 2 pounds 



Water 50 gallons 



Without the addition of soap, the material is fairly effective; 

 but when combined with the soap, its killing power is considerably 

 increased. 



Sulphur sprays. — While the sulphur sprays possess an exten- 

 sive field of usefulness in horticultural activities in the country, it 

 is more limited in city spraying. As strong dormant sprays they 

 are used principally for the control of scale insects of the' classes 

 represented by the San Jose scale, scurfy bark louse, and the like ; 

 that is, most of the scale groups other than the large fleshy types, 

 of which the magnolia and terrapin scales are examples. This lim- 

 itation is due in large part to the fact that the sulphur sprays com- 

 bine chemically with the paint on houses, resulting in serious dis- 

 coloration and disfigurement. The soluble or miscible oils do not 

 possess this disagreeable property, however; and, since they are 

 equally effective for most of the troubles for which the sulphur 

 sprays are used, they are gradually replacing the latter group in 

 city operations, particularly for street use. Nevertheless, the 

 sulphur-carrying sprays cannot be discarded completely from city 

 work ; indeed, in park and boulevard spraying they may be employed 

 extensively for years to come. They therefore merit a fairly com- 

 plete discussion. 



Home-boiled lime-sulphur. — For 15 years or more the home- 

 boiled lime-sulphur has been used successfully in controlling San 

 Jose scale and similar scale insects, having been the first really 

 successful spraying material devised for this purpose. Moreover, 

 it furnished the basis for our modern concentrated sulphur sprays ; 

 and, while great progress has been made in the devising of new 

 forms, the fact still remains that some growers have returned to 

 the use of the home-boiled product after having employed the so- 



