Important Obohabd Pests and Speay Formulae. 485 



gallons of water, makes a spray particularly useful against plant 

 lice in summer. 



Commercial Tobacco Extracts. — These are rapidly coming to 

 the front for use against plant lice and pear psylla. The strength 

 of dilution required depends on percentage of nicotine present, 

 which should be guaranteed. 



LIME-SULPHTTB 



Lime-sulphur washes have both insecticidal and fungicidal 

 qualities. For scale insects the winter strength has long been 

 used, and blister mite and the leaf curl of peaches are controlled 

 by this same application. As originally made, the weight of lime 

 used was greater than the weight of sulphur. This material 

 formed crystals on cooling and consequently was only prepared 

 as required. Professor Cordley, of Washington, introduced a 

 formula in which the weight of lime is about one-half as great as 

 the weight of sulphur and thus changed the mixture. This keeps 

 almost indefinitely if contact with the air is prevented. It is 

 possible to avoid nearly all sediment if a proper grade of lime be 

 used and the wash can be boiled in concentrated form. Several 

 modifications of the Cordley formula have developed during the 

 past three years. The Greneva formula gives but little sediment 

 with proper lime and unites the lime and sulphur in the best 

 forms, although not so concentrated as in the Cordley formula. 



The Geneva Formula for Concentrate* — Thirty-six pounds of 

 lime (based on pure lime, CaO), 80 pounds of high-grade, 

 finely divided sulphur and 50 gallons of water. When lime con- 

 taining 95 per cent, or less than 95 per cent, of calcium oxid is 

 used, more than 36 pounds must be taken, according to amount 

 of impurities (38 pounds for 95 per cent, lime and 40 pounds 

 for 90 per cent, lime) but no lime should be used containing less 

 than 90 per cent, of calcium oxid or more than 5 per cent, of 

 magnesium oxid. In boiling the solution, the liquid must not be 

 allowed to drop more than slightly below the 50 gallon level. 



Never use air-slaked lime or lime less than 90 per cent. 

 pure or containing over 5 per cent, of magnesium oxid. Ground 

 crystalline sulphur is not usually fine enough, but either flowers 

 or the commercial Hour of sulphur is sufficiently fino. The water 

 is first heated and the lime and sifted sulphur added, or the 



* See New York State Agricultural Experiment Station Bulletin 329. 



