EXPERIMENT STATION BULLETINS. 479 



This summary shows that the standard lime-sulphur solution has given 

 in every experiment better control of apple scab than any of the dry lime- 

 sulphurs or similar materials. 



DUSTING FOR THE CONTROL OP PEACH LEAF-CURL. 



A test was made at Saugatuck in the spring of 1919 to determine if leaf- 

 curl can be controlled by the use of dusting materials. The results obtained 

 from the use of sulphur dust and soluble sulphur dust were entirely unsatis- 

 factory as neither gave any degree of control. This experiment has been 

 reported in detail in Special Bulletin No. 102. 



Another similar test was made in 1920 at South Haven on the farm of Mr. 

 Jas. Nicol. The trees were mature and the variety was Marshall's Late. 



Materials and application. Two plots were dusted, two sprayed and one 

 left untreated as a check. The materials used were as follows : 



1. Lime-sulphur solution, 23^ gal. in 50. 



2. Lime-sulphur solution, QJ4 gal. in 50. 



3. Soluble Sulphur Dust (Niagara). 



4. Bordeaux dust (Niagara). 



5. Check. No treatment. 



The materials were all applied during the last week of March and the trees 

 were entirely dormant at that time. 



Results. Weather conditions were not most favorable for leaf-curl devel- 

 opment and the disease did not develop seriously even on the check trees, 

 but there was sufficient infection to give a comparison. The trees were 

 examined at different times, the last of which was early in June when the 

 following comparisons were made. 



The trees in both sprayed plots were practically free from curled leaves. 

 The trees in both dusted plots showed some leaf-curl but not to a large degree. 

 The check trees had many curled leaves but little defoliation had occurred. 



The results of this experiment are not conclusive if considered alone but 

 when considered with the results obtained in 1919, the conclusion must be 

 made that satisfactory control of peach leaf-curl has not been obtained with 

 dusts. 



Lime-sulphur solution, 23^-50, gave results in this experiment equal to 

 the results obtained from the use of lime-sulphur solution, 63^-50. 



Grape Dusting Experiments. 



Dusting experiments with grapes have been in progress during the seasons 

 of 1920 and 1921 but no conclusive results have been obtained from this 

 work. Dusting materials have been used for the control of black rot, the 

 grape berry moth and grape leaf -hoppers, but it will be necessary to continue 

 this work before any definite statements can be made as to the comparative 

 value of the dusting and spraying methods for the control of grape pests. 



Potato Dusting Experiments. 



Potato dusting experiments were begun in 1920 and continued in an exten- 

 sive way in 1921. Work was carried on at Paw Paw, Van Buren County; 

 Manton, Wexford County; Alba, Antrim County; Boyne City, Charlevoix 

 County, and Levering, Emmett County. Power dusters were used at some 

 places and hand dusters at others. A detailed statement concerning the 

 experiments and the results obtained will not be included in this report but 

 the work will be continued and a report made later. 



