10 



as much as the sludge in the mixture containing calcium caseinate. Apparently the 

 addition of calcium caseinate physically improves the mixture. 



In filling the spray tank, five ingredients are or may be used, i.e., water, lime- 

 sulfur, lead arsenate, nicotine sulfate and calcium caseinate. After the water 

 is in the tank, there are twenty-four different orders in which the other ingredi- 

 ents may l^e added. The manufacturers of calcium caseinate recommend that it 

 be added to the water in the spray tank, with the agitator running, before the other 

 materials are added. According to Anderson and Roth (22) the hme-sulfur is first 

 diluted, the lead arsenate added to it wnth agitation, and then the nicotine sulfate 

 added. After putting the calcium caseinate in the water in the spray tank, this 

 is probably the order most commonly followed. Britton (23) recommends the 

 following order for fiUing the spray tank: first, clean water; second, nicotine sul- 

 fate; third, calcium caseinate (if used); fourth, lead arsenate; and fifth and last, 

 lime-sulfur. He saj^s that when mixed in this order, especially if calcium caseinate 

 is present, httle or no discoloration or precipitation of brown sludge follows. 



In laboratory tests made by the writer, the ingredients were mixed in the order 

 named by Britton; the resulting mixture was buffy olive in color, with little pre- 

 cipitation. In another test they were mixed in the following order : water, calcium 

 caseinate, lime-sulfur, lead arsenate, and nicotine sulfate. The color of this mixture 

 was iv3^ green, considerably darker, with more precipitation. Several other orders 

 of mixing were compared and the best results, based on a color test and relative 

 sludge formation, were obtained by the follo^ving sequence after the water: first, 

 calcium caseinate; second, nicotine sulfate; tlurd, lead arsenate; and fourth, 

 lime-sulfur. 



Spore germination tests made ^\^th the conidia of the apple scab fungus showed 

 that the fungicidal efficiency of the combination spray is not impaired by any 

 order of mixing tested. But the order of mixing does affect the physical qualities 

 of the mixture and very probably the burning of the spraj'ed tree. It should be 

 added that when light colored lime-sulfur combination spray is desired, special 

 attention should be given to washing out the spray tank. The use of calcium 

 caseinate results in a decidedly lighter colored mixture. 



Results of Dusting Treatments. 



A rather extensive literature on the results of dusting for the control of apple 

 scab has come into existence. The results do not all agree, but perhaps they are 

 no more inconsistent than the pubhshed results of spraying experiments. In gen- 

 eral, the control of apple scab by the use of dusts has been surpassed by that of 

 liquid spra5^s. This is not surprising when we consider that spraying is a much 

 older orchard practice than is dusting. Our knowledge of the use of liquid sprays 

 and the schedule for their appHcation to the apple is relatively advanced. Dusts 

 have been used in conformity with the spray schedule, rather than according to 

 any special dusting schedule. 



It should be noted that no experiments have been conducted in Massachusetts 

 which directly compare the results of spraying with those of dusting. Owing to 

 the topography and plan of the several orchards, spraying and dusting experiments 

 have been carried on in separate orchards or in separate parts of the same orchard 

 \\ith one check plot for the spray treatment and another for the dust treatment. 



In the orchards dusted by Krout (2) in 1922 the average percentage of scabby 

 fruit in the check plots was 75.8 and the average percentage of scabby fruit in the 

 plots dusted with sulfur was 17.2. In the orchards sprayed by Krout, the average 

 percentage of scabby fruit in the check plots was 79.0 and the average percentage 

 of scabby fruit in the plots sprayed with dry lime-sulfur 4-50 was 8.0. It is evi- 

 dent that the dust did not give a control equal to that of the spray. The results 

 of Massey and Fitch (8) were: in one orchard, check 93.3 per cent scab, and sulfur 

 dust 13.5 per cent scab; in another orchard, check 43.5 per cent scab and sulfur 

 dust 3.1 per cent scab. In an orchard dusted by Parrott, Stewart, and Glasgow 

 (13), the results were 83.9 per cent scab in the check, and 47.8 per cent scab in the 

 plot dusted with sulfur. Results from other years and other states could be selected 

 either in favor of or against dusting. 



In 1923, the dusting experiments here reported were conducted in three orchards. 

 At the Stowe and the Sabine orchards, the dusting schedule consisted of five appli- 



