4 DECIDUOUS FKUIT INSECTS AND INSECTICIDES. 



the vines had each season made a weaker growth as a result of injury 

 by this pest, and the yield of fruit also was being greatly reduced. 



During the season of 1910 several acres on the east side of this 

 vineyard were sprayed with tobacco extract No. I. This treatment 

 resulted in preventing serious injury by the insect. The foliage re- 

 mained green and healthy throughout the season. There was a 

 greatly increased growth of vine and a higher quality of fruit was 

 secured. The greatest apparent benefit in 1910 was in the great 

 increase in growth of vine. 



During the season of 1911 the entire vineyard of 25 acres was 

 sprayed against this pest, which was present in fully as large num- 

 bers as in 1910. 



A tractor sprayer was used in making the application. (See PL I, 

 fig. 1.) A pressure of 100 to 140 pounds was maintained and about 

 175 gallons of liquid were applied per acre. The application was 

 made by the owner of the vineyard, Mr. H. H. Harper. The spray 

 was applied by the "trailer" method (see PL I, fig. 1), using a single 

 large cyclone nozzle. The work was done very carefully and thor- 

 oughly. Stops were made at each vine. The pressure was main- 

 tained by driving forward the length of the trailer hose. By having 

 a 20-gallon air-chamber on the tractor sprayer a pressure varying 

 from 100 to 140 pounds was secured, rarely dropping below the 100- 

 pound mark. Under favorable working conditions about 3 acres 

 could be covered per day. The tobacco extract No. I was applied 

 at a dilution of 3 quarts to 100 gallons of water. The application was 

 made, on the 3 acres from which our record of yield was secured, on 

 July 6 and 7, when the majority of the nymphs were small but very 

 numerous. The application was very effective, and on account of 

 the thoroughness with which the work was done only a very small 

 percentage of nymphs escaped being killed by the spray. 



As a result of this treatment the foliage of the vines remained green 

 throughout the entire season, and the vines made a very heavy 

 growth of new canes. The berries and clusters of fruit were large 

 and of good quality. A record has been kept of the yield for the past 

 three years on 3 acres of this vineyard where the injury by this 

 insect was most apparent at the beginning of the experiment. No 

 attempt to control this pest on these vines was made previous to 1910. 



1909 Yield of fruit was 262 8-pound baskets of grapes per acre. 



1910 Yield of fruit was 423 8-pound baskets of grapes per acre. 



1911 '.Yield of fruit was 796 8-pound baskets of grapes per acre. 



These results show an increase in yield on the first season's treat- 

 ment of 161 baskets per acre, and for the second season's treatment 

 an increase of 534 baskets per acre over the yield of 1909. 



Since the price received per basket of grapes varies each season , it 

 is difficult to compare cash returns one season with another. Prices 



