6 



as liquid lime-sulfur against apple scab. In most of the experiments of Keitt and 

 Jones (7) , the results with dry lime-sulfur in controlling apple scab were similar to 

 those obtained with hquid lime-sulfur. Massey and Fitch (8) had practically 

 the same results with dry as with liquid lime-sulfur. 



Dry lime-sulfur is less bulky to transport. But the material necessary to make 

 100 gallons' of spray costs about twice as much in the dry form as in the hquid. 

 The so-called free sulfur in dry lime-sulfur does not redissolve in water, and this, 

 according to Sears (9), wears out pumps and nozzles more rapidly than does liquid 

 lime-sulfur. It may be added that if this objection is valid, it will hold none the 

 less for dry-mix sulfur-hme, or any sulfur fungicide other than a solution. It seems 

 that the orchardist must decide for himself whether to use dry or liquid lime-sulfur, 

 but he may be sure that the fungicide in either form is efficient for the prevention 

 of infection by the apple scab fungus. 



Concentration at Which to Use Dry Lime-Sulfur. 



Trees sprayed with dry Ume-sulfur 4-50 yielded on the average 1.3 per cent 

 scabby apples as compared to 60.7 per cent on unsprayed trees; while trees sprayed 

 with dry lime-sulfur 2-50 and dry lime-sulfur 3-50 yielded 3.9 and 5.8 per cent 

 scabby apples respectively, as compared to 67.6 per cent on unsprayed trees. The 

 indications are that the use of less than 4 pounds of dry lime-sulfur in 50 gallons will 

 be followed by a slight increase in the percentage of scabby apples. 



Krout (2) secured similar results. The check plot yielded 41 per cent scabby 

 fruit, the dry lime-sulfur 4-50 plot yielded 2 per cent, and the dry lime-sulfur 3-50 

 plot jdelded 4 per cent scabby fruit. The difference was slight in 1922 as it is in 

 1923, but the variation is in the same direction. 



Whether liquid or dry lime-sulfur is used, the protection afforded is dependent 

 ilpon the amount of sulfur present in the diluted spray. The percentage of sulfur 

 is of course not always the same in all dry lime-suKurs. But in general it may be 

 said that not less than 4 pounds of dry lime-sulfur in 50 gallons are required to 

 supply the same number of pounds of sulfur as are present when 1 gallon of com- 

 mercial concentrated lime-suKur, of the usual strength tested in degrees Baum6, is 

 diluted to 50 gallons. According to Dutton (10) the amount of dry Ume-sulfur 

 necessary to furnish the equivalent amount of sulfur in 50 gallons is 4.4 pounds, and 

 according to Eustace and Pettit (11), it is 4.8 pounds. 



The evidence submitted indicates that reducing the amount of dry lime-sulfur _™ 

 below 4 pounds to 50 gallons is a practice of doubtful economy. m 



Effect of a Calcium Caseinate Spreader on Control of Scab. 



The percentage of scabby fruit was reduced slightly by the addition of calcium 

 caseinate spreader to lime-sulfur. At Frost's, this reduction was from 7.06 to 5.08 

 per cent scabby fruit; and at Knights', the reduction was from 4.6 to 0.68 per 

 cent. It is a question whether these reductions are in themselves large enough to 

 be significant, but the results are consistently in favor of the use of the calcium 

 caseinate. 



The addition of calcium caseinate to sulfur dust did not result in a reduction in 

 the percentage of scabby apples, as compared with the plots dusted with sulfur 

 alone, in either the Frost or the Sabine orchard; and in the Stowe orchard the 

 results were practically the same. In the Frost orchard, the addition of calcium case- 

 inate spreader to sulfur dust was followed by a considerable increase in the per- 

 centage of scabby apples. 



In the spreader tests of Stearns and Hough (12) the addition of calcium caseinate 

 did not increase the effectiveness of the spray in protecting fruit and foUage from 

 disease and insects. Keitt and Jones (7) secured slightly better control of scab 

 when calcium caseinate was added to lime-sulfur than when the latter was used 

 alone, but it was not considered that the commercial value of its addition was 

 determined. Trees sprayed with hme-sulfur by Parrott, Stewart, and Glasgow (13) 

 jdelded 2.1 per cent scabby apples, while trees sprayed with Ume-sulfur with calcium 

 caseinate added yielded 4.8 per cent scabby apples. In the experiments of Massey 

 and Fitch (8) trees sprayed with hme-sulfur yielded 1.2 per cent scabby apples, 

 and those trees which were sprayed with hme-sulfur with calcium caseinate added 



