CONTROL OF GRAPE-BERRY MOTH. 23 



The dust materials were applied with a small hand duster and 

 the liquids with a gasoline power sprayer. In each case the appli- 

 cation was made from either side of each row and a thorough cover- 

 ing of foliage and fruit effected. The dust materials adhered to the 

 grape foliage fairly satisfactorily but did not adhere well to the 

 smooth surface of the grape berries. No rain fell from the time of 

 the application until August 11 when a light shower occurred. 

 When the vines were examined on August 19 only a trace of the 

 dust material was in evidence on the foliage or fruit, while the 

 sprayed fruit was well covered with spray material. It required 40 

 pounds of dust material to dust 46 thrifty Catawba vines. At this 

 rate and with the vines set 900 to the acre as is the practice in this 

 section, it would require T83 pounds of material per acre. No doubt 

 this would be materially reduced if a power machine were used 

 for the dusting. If but half as much material were required per 

 acre the amount of arsenical would be from 6 to T times as great 

 as when applied in liquid form at the rate of L| pounds of arsenate 

 of lead powder to 50 gallons of spray and the liquid applied at the 

 rate of 200 gallons per acre. The writers feel that the dust would 

 have to be applied much more frequently than the liquid to be ef- 

 fective for berry moth control. This method of application might 

 be satisfactory for treating small home grape arbors when applied 

 frequently. 



Spray Residue on Gbapes at Harvest Time. 



Throughout these investigations records were kept on the com- 

 parative amounts of spray residue on the grapes at harvest time. 

 In all cases where the spray application shown as the third (fig. 1) 

 was used in early August the fruit was heavily coated with spray 

 material at harvest time. In nearly all cases where the combination 

 of first and second sprays was used, and spraying completed by 

 July 25, there was not sufficient spray residue at harvest time to 

 affect the marketing of the grapes in baskets for table use. When 

 either the first or second application was used alone the residue was 

 lighter than when both were used. Slightly more residue resulted 

 on the plats sprayed with arsenate of lead at the rate of 2^ pounds 

 than on those sprayed with the same material at the rate of \\ 

 pounds to 50 gallons. No difference could be seen between the fruit 

 from plats on which Bordeaux was included and those on which 

 lime, 2 pounds to 50 gallons, was substituted for it. Slightly less 

 residue was present on the plats sprayed with arsenate of calcium 

 than on those sprayed with arsenate of lead where the comparison of 

 material was on the basis of arsenical content. In one plat where 

 these materials were mixed in the proportion of arsenate of calcium 

 9 ounces to arsenate of lead 5 ounces, the amount of residue was 



