EXPERIMENT STATION WORK WITH INSECTICIDES. 241 



effective with the lime and potassium sulphid mixture recommended 

 by that station. The California wash was much more satisfactory 

 than whitewash or strong Bordeaux mixture, for the reason that it 

 remained nnich kmger on the trees after the occurrence of rain. The 

 Oregon wash, in which copper sulphate was substituted for salt, soon 

 disappeared from the trees, although in some instances it was very 

 effective in destroying the scale. During the spring of 1903 Con- 

 necticut orchardists are reported to have tested lime-sulphur mix- 

 tures on about 40,000 trees with very satisfactory results. In the 

 experiments at this station lime and sulphur mixtures remained long- 

 est on the trees when applied just before the leaves appeared. The 

 reason for this seemed to be that the leaves protected the washes from 

 the spring rains. In orchards where two applications were made, 

 one in late fall and one in the spring, the San Jose scale was nearly 

 eradicated. The same station followed up this line of work in the 

 succeeding season with further experiments on 4,000 orchard trees of 

 various kinds, using 15 different formulas of lime and sulphur combi- 

 nations. In these tests it was found that where the spraying was 

 done as soon as the leaves fall a large proportion of the young scales 

 was killed, since the}^ are then more susceptible than later. In com- 

 paring the 15 different formulas of boiled and unboiled mixtures of 

 lime and sulphur it appeared that a boiled mixture containing an 

 equal quantity, or a little more or a little less, sulphur was as effec- 

 tive and cheap as any of the mixtures for ordinary orchard work. 

 The unboiled mixtures contained lime and either potassium sulphid, 

 sodium sulphid, sulphur, or a combination of sulphur and sodium 

 sulphid, or sulphur and caustic soda. The combination of lime, sul- 

 phur, and sodium sulphid gave excellent promise of becoming a sat- 

 isfactory insecticide. Caustic soda seemed to possess certain disad- 

 vantages, particularly the unpleasantness of handling it. During the 

 season of these direct exi)eriments by the station about 100,000 fruit 

 trees were sprayed with these mixtures in Connecticut with generally 

 satisfactory results. 



During the spring of 1905 the Connecticut Storrs Station " con- 

 tinued its experiments with sulphur compound in combating San 

 Jose scale. As a result of all the investigations at this station it is 

 concluded that it is not possible to kill all of the scales on infested 

 trees for the reason that the spray does not come in contact with all 

 of tlie insects. In tests of lime and sulphur mixtures, however, from 

 91 to 95 per cent of the scales were killed. The presence of salt in the 

 mixture did not add anything to the adhesive qualities of the insecti- 

 cide nor to its effects upon the scale. Of all the various proportions 

 <»f lime and sulphur used the most effective was one in which the 



o Connecticut Storrs Sta. Bui. 30. 

 H. Doc. 024, 5D-1 10 



