CONTROL OF GRAPE-BEERY MOTH. 11 



The experiments were extended in 1918 to include work in 15 vine- 

 yards, but as infestation was not sufficiently heavy for satisfactory 

 comparisons in all the vineyards only the 5 showing the heaviest 

 infestations are included in Tables III and IV. 



The arsenicals were applied in Bordeaux 2-2-50 in vineyards Nos. 

 1, 2, and 5. In vineyards Xos. 3 and 1 copper sulphate was omitted 

 at the request of the owners. Stone lime 2 pounds to 50 gallons was 

 retained to care for any free arsenic in the arsenicals. Resin fish-oil 

 soap at the rate of 1 pound to 50 gallons was used uniformly through- 

 out the experiments. 



METHOD OF RECORDING RESULTS OF SPRAYING EXPERIMENTS. 



It had been learned in earlier work 1 that results based on weights of 

 harvested fruit were misleading, owing to the varying thrift of vine- 

 yards, time of harvest, weather conditions affecting the development 

 of worms, etc. The weight method, therefore, was abandoned in 

 favor of the count method. This consists in selecting a representa- 

 tive number of vines in each sprayed plat and in each check, har- 

 vesting all the fruit from these vines, counting the clusters, then 

 the clusters containing wormy berries, then removing the wormy 

 grapes and counting them. To ascertain the average number of 

 grapes per cluster, 100 representative clusters were taken in each 

 vineyard and all the grapes counted. The number of clusters in 

 each plat was then multiplied by the average number of grapes per 

 cluster to give the total number of grapes examined in each plat. 



In all control work on the grape-berry moth, the unevenness of in- 

 festation within a vineyard has made experimental results difficult to 

 interpret. This uneven infestation prevailed throughout these in- 

 vestigations but was cared for whenever possible by placing checks 

 across the control plats and reading the results on the control plat 

 the second post-length away from the checks. While the plan does 

 not entirely overcome the difficulty,. the writers feel that the averages 

 from several vineyards closely approximate actual conditions. 



In all cases the fruit from at least 10 vines was examined and when 

 possible the examinations included all the fruit from 20 to 25 vines. 

 Exceptions to this occurred only when there were less than 10 vines 

 of a particular variety in a plat. First-brood counts were made in 

 some instances, but since they add little to the final results they are 

 omitted from the tables. 



1 Johnson, Fred, and Hammar, A. G., op. cit. ; Isely, Dwight, op. cit. 



