COMBATING APPLE SCAB. 35 



Dusting Program for 1922. 



The use of dusts for the control of apple scab is new in this State. 

 Prior to 1921 the writer knew of only one dusting machine in the eastern 

 part of the State, and that was used for dusting peaches. In 1921 dusting 

 experiments were begun by the station in three orchards. The writer 

 and growers who co-operated were inexperienced in the art of dusting, 

 and consequently the dusts were not applied as well as they might have 

 been. As a result, dusting compared very unfavorably with spraying. 



In 1922 a number of growers bought dusting machines. With the 

 experience of the previous year, and willingness on the part of growers to 

 co-operate, extensive plans were made to test the efficacy of dusting 

 materials for the control of apple scab. Accordingly, five orchards, 

 previously mentioned, were chosen in which to locate the experiments. 

 Two dusts, sulfur and a copper-lime-arsenate dust, were used in each 

 orchard. Checks were used in all cases. The plots were all large, one 

 of them containing 179 trees. Only Mcintosh trees were used. 



It will be noticed that there was no nicotine in any of our dusts. Nico- 

 tine makes a dust expensive, and the manufacturers state that it is diffi- 

 cult to manufacture a satisfactory sulfur dust high in sulfur with sufficient 

 nicotine in it. As it happened, no nicotine was needed on any of the 

 plots, but it was planned to spray with a nicotine solution or dust with a 

 nicotine dust should infestation with sucking insects become serious. 



Five representative trees of each dusted plot in the Marshall and Stowe 

 orchards, 7 in the Knights orchard and 6 in the Frost orchard were chosen 

 from which to take data. Also 3 representative trees of each undusted 

 check in the Marshall and Knights orchards, 2 of one check in the Stowe 

 orchard and 3 of the other (Table VII, plot 12) and 2 in the Frost orchard 

 were chosen from which to take the data (Tables V, VI and VII, pages 

 40 and 41). The data of the Fiske orchard are not given as the trees were 

 3'oung and the j'ield exceptionally low. 



Treatment of Plots. 

 Plots 13 and 14 in all the orchards were given the regular delayed- 

 dormant spray with lime-sulfur. The plots in the Stowe orchard were 

 given three dust applications, • — the pre-pink, pink and fourth summer. 

 The plots in the Frost and Fiske orchards had four applications, — the 

 pre-pink, pink, calyx and fourth summer. The plots in the Knights 

 orchard had five applications, — the pre-pink, pink, calj'^x, fourth and 

 fifth summer. The plots in the Marshall orchard had nine applications, 

 — the pre-pink, pink, calyx and six subsequent applications. The detailed 

 treatment of plots follows: — 



Plot 12. — Check untreated with fungicides, but sprayed with the usual insecti- 

 cides. 



Plot 13. — Sulfur dusts. The ordinary commercial dusting sulfur without in- 

 secticides was used for the pre-pink, fifth, sixth and seventh summer applications. 



