36 MASS. EXPERIMENT STATION BULLETIN 214. 



A sulfur dust, composed of 85 parts sulfur and 15 parts arsenate of lead, was used 

 for the pink, calyx and fourth summer dusts. 



Plot 14. — Copper-lime-arsenate dust for the pre-pink, pink and fourth summer 

 applications only. An 85-15 sulfur dust was used at the calyx application, and 

 dusting sulfur for treatments after the fourth summer application. 



Time and Manner of Application. 

 The dusts were applied at approximately the same time as the sprays 

 (Table II). Two different makes of power dusting machines were used. 

 The dusts were applied from two sides of the trees while the leaves were wet. 

 Dusting was started at 5 a.m. and continued until about 8 a.m. The best 

 distribution of dust through the tree was accomplished by giving the 

 hose a circular or a quick upward and downward movement. Care was 

 taken to hit the lower leaves, especially at the pre-pink and the pink 

 applications. The engine and duster should be on a low wagon or truck 

 built especially for the purpose, so that the operator may shoot the dusts 

 upward through the tree. Where rows of trees are too close together, 

 this will hinder the operation of the duster. 



Discussion of Results of Dusting. 



In evaluating the results from dusting in 1922 it must be borne in mind 

 that only a single year's work is represented, and that it is, therefore, 

 decidedly unsafe and unsound to draw any conclusions whatever. 



The data in Tables V, VI and VII show that the dusts gave excellent 

 control of scab in a year most favorable for the development of the scab 

 fungus. For example, in the Knights orchard the check for the dusts 

 produced only 1 per cent marketable fruit, while the sulfur and copper- 

 lime-arsenate dust plots produced 97 and 99 per cent marketable fruit. 

 In the Frost orchard the check for the dusts produced 68 per cent mar- 

 ketable fruit; the sulfur dust plot, 96 per cent; and the copper-lime- 

 arsenate plot, 97 per cent. 



In the Stowe orchard the checks produced from 46 to 48 per cent mar- 

 ketable fruit; the dusted plots, 92 to 97 per cent. Table VII shows that 

 in the Stowe orchard slightly better results were obtained on the younger 

 trees than on the older. This, with the fact that practically all the scabby 

 apples of the dusted plots Avere found in the tops of the trees, would 

 indicate that the higher the tree the more difficult it is to apply the dust 

 thoroughly. Although the results on the dusted plots were extremely 

 good, it is evident that even better results might have been obtained had 

 the dusts been more thoroughly applied to the topmost parts of the trees. 



In several cases where late summer applications of lime-sulfur and 

 dusts were made side by side in the same orchard, the lime-sulfur burned 

 the foliage, while the sulfur dust caused no injury. Later observations 

 showed that where the foliage was burned by the lime-sulfur, from 8 to 

 20 per cent of the fruit dropped prematurely; while where the sulfur 

 dust was used, practically the entire crop remained on the trees. 



