SPRAYING AGAINST GRAPE LEAFHOPPER. 5 



number of the insects so that those remaining did not materially 

 affect the growth of the vine or the proper ripening of the fruit. 



These experiments were conducted in different parts of the town- 

 ship and several types of sprayers were used in making the applica- 

 tions. In all cases the "trailer" method was employed; that is, a 

 trailing hose about 20 feet long was connected to the discharge of the 

 spray pump and a short rod, about 2J feet long, carrying a large nozzle 

 of the cyclone type set at right angles to the rod was attached to the 

 free end of this lead of hose. This rod is held by the operator, who 

 thrusts the nozzle among the foliage with rapid movements, directing 

 the nozzle upward, so that the liquid is thrown upon the underside of 

 the leaves. (See PI. I, fig. 1.) 



Two forms of commercial tobacco extract were used in these experi- 

 ments: No. I (blackleaf extract) contained 2.70 per cent nicotine; 

 No. II (blackleaf 40) contained 40 per cent nicotine sulphate. In 

 all of the experiments which follow the tobacco extracts are refer- 

 red to by number. Tobacco extract No. I refers to the form con- 

 taining the lower percentage of nicotine, tobacco extract No. II to 

 the form containing the higher percentage of nicotine. At the dilu- 

 tions used no decided advantage was evidenced in favor of either 

 form of tobacco extract. Both of these substances killed the nymphs 

 that were hit by the spray. The tobacco extract No. I at a dilu- 

 tion of 1 part of extract to 150 parts of water killed all nymphs 

 that were' made thoroughly wet by the spray, especially the smaller 

 nymphs, between the first and fourth molts. The full-grown nymphs, 

 unless thoroughly soaked by the spray at this dilution, would some- 

 times escape, probably because their longer legs held their bodies 

 some distance from the wet surface of the leaf. The tobacco ex- 

 tract No. II was effective at a dilution of 1 part of extract to 

 1,500 parts of water. In the use of the tobacco extract No. II — 

 as with the tobacco extract No. I, where a large percentage of 

 the nymphs were in the last stage; that is, just about to develop 

 wings (see fig. 3) — a dilution of 1 to 1,200 or 1,300 may be more 

 effective in killing the nymphs. In the several experiments con- 

 ducted, however, the dilutions varied from 1 to 100 parts of water 

 to 1 to 150 with tobacco extract No. I, and from 1 to 1,000 to 1 to 

 1,500 with tobacco extract No. II. In all of these variations of dilu- 

 tion apparently equally good results were obtained. 



VINEYARD EXPERIMENTS IN 1911. 



EXPERIMENT IN VINEYARD OF MR. H. H. HARPER, NORTH EAST, PA. 



The east side of the vineyard of Mr. H. H. Harper, North East, Pa., 

 adjoining the highway had been badly infested by the grape leafhopper 

 for several years. Previous to the undertaking of this experiment 



