306 Report of the Depaetment of Entomology of the 



sugar than the lower one and on another vine the difference was 

 9.7 per ct. 



(4) The amount of acid was greater in grapes from the lower 

 portions of the vine than from the upper portion of the same 

 vine. 



CONCLUSIONS DEDUCED FROM THE EXPERIMENTS. 



These experiments were designed to test out the recommenda- 

 tions given in previous bulletins.* The Station has now conducted 

 experiments for three years with nicotine extract, and two years 

 with the automatic leaf-hopper sprayer. From the work done 

 during these years the following points should be noted : 



(1) Nicotine at the rate of .02 of one per ct. either in water 

 or bordeaux mixture is an effective insecticide against the nymphs 

 of the grape leaf-hopper. 



(2) During three seasons there has been no burning of the 

 grape foliage by the nicotine sulphate or nicotine in other forms 

 used in our experiments ; nor has the taste of nicotine been found 

 on ripe grapes. 



(3) Although it is necessary to combat the pest during its 

 nymphal existence there is considerable time during which effec- 

 tive spraying can be done. The operations during 1912 covered 

 a period of 15 days or half a month; but during years with hot 

 weather during July the transformations are more rapid and ten 

 days would be a safer margin for effective work. 



(4) The automatic grape leaf-hopper sprayer has given satis- 

 faction in the hands of careful grape growers. Carelessness in 

 driving will bend or even break the booms, but with an average 

 amount of care no trouble has been experienced with the attach- 

 ment. Several manufacturers have attached the contrivance to 

 their spraying machines, which gave satisfactory results, when 

 pumps worked properly. 



(5) Grapes from vines protected from leaf-hoppers had a 

 higher percentage of sugar and less acid, and were of a darker 

 color than grapes grown under identical conditions but subjected 

 to the attacks of the insects. 



New York Agrl. Expt. Sta. Buls. Nos. 331 and 344. 



