DIPPING AND FUMIGATION OF NURSERY STOCK 23 



LIME-SULPHUR FIRST USED 



On page six, under "Control in the Orchard," a discussion of the 

 first use of lime-sulphur for the control of insects is given. 



F. A. Sirrine of New York Agricultural Experiment Station was prob- 

 ably the first to dip nursery stock for the control of San Jose scale. He 

 dipped some nursery stock in 1894 on Long Island with a whale-oil soap 

 preparation. Lime-sulphur was probably first used as a dip for nursery 

 stock for the control of the scale by Professor C. V. Close of the Deleware 

 Experiment Station in 1903. 



Used up to present time. Since 1894 a large number of experiments 

 have been made with lime-sulphur as a tree dip for the control of San Jose 

 scale but none have been, on the whole, entirely successful. In some cases 

 the scale was controlled but the most serious objection to using it was the 

 fact that in nearly every case the plants were injured to a greater or less 

 extent. Although lime-sulphur is used almost altogether for controlling 

 San Jose scale on old trees, it has never proven to be a practical success for 

 dipping nursery stock. 



Methods for using. When lime-sulphur is used upon nursery stock as 

 a spray for the control of San Jose scale, it is during the dormant season 

 while the trees are still in the nursery row. It is applied at the usual rate, 

 the same as recommended for mature trees, 1 to 7, and is put on with a 

 spraying machine, either hand or power. Most large nurseries have espe- 

 cially constructed spraying machines which are built so as to be easily 

 gotten between nursery rows. 



When lime-sulphur or any other material is used for dipping nursery 

 stock a vat is constructed or a trough made which is large enough to hold 

 sufficient liquid to immerse an entire tree. 



Chemical composition of lime-sulphur. Lime-sulphur is made by boil- 

 ing in water slaked rock lime containing not less than 95 per cent calcium 

 oxide and flowers of sulphur. A very complicated chemical reaction takes 

 place when lime and sulphur are boiled together in water. The sulphur (S) 

 combines with the calcium (Ca) in the lime (CaO), in varying amounts, with 

 the result that two compounds are formed calcium tetrasulphide (CaSO, 

 containing 76 per cent of sulphur. Also a small quantity of thiosulphate 

 (CaSsOs) is formed. These compounds formed are soluble in water and it is 

 to them that the insecticidal value of the mixture is due. The higher the 

 oercentage of pentasulphide, the more effective is the mixture. In making 

 the lime-sulphur solution it is necessary to boil it for an hour in order to 

 form a complete chemical union of the lime and sulphur. Two parts of sul- 

 phur combine with one part of lime and in making the solution, twice as much 

 sulphur as lime should be used. 



RESULTS OF EXPERIMENTS WITH LIME-SULPHUR 



As the lime-sulphur wash has become the most standard spray for the 

 control of San Jose scale on infested fruit trees, the writer saw no reason 

 why it should not be used to dip infested nursery stock. 



