10 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



weeks in July. At this time also larvae of the grapeberry moth are 

 hatching from eggs deposited upon the grape berries. Since it is 

 impossible to cover thoroughly the underside of the grape leaves in 

 spraying for the grape leafhopper without thoroughly wetting the 

 grape clusters it is reasonable to infer that the addition of arsenate 

 of lead would also assist in checking the injury to the grape berries 

 by the larvae of the grape berry moth. In addition to this the Bor- 

 deaux mixture will control the development of mildew on the stems 

 of the grape clusters. The upper surface of the grape leaves also is 

 covered during this process (see PL III, fig. 2) ; hence, if arsenate of 

 lead is present with the tobacco extract this application will control 

 the late emerging beetles of the grape rootworm. As intimated 

 above, the advisability of making this combination of ingredients 

 must be decided by the prevalence and abundance in the vineyard 

 to be treated of the several insects referred to. It should also be 

 borne in mind that this combination treatment is submitted as a 

 suggestion. 



The mixing of the tobacco extracts with Bordeaux and arsenate of 

 lead this season was done for the sole purpose of determining if this 

 mixture would be injurious to the grape foliage and berries. As men- 

 tioned above, no injurious effect to the vine was observed. Arsenate 

 of lead is the only arsenical that should be used with tobacco extracts, 

 since both arsenite of lime and Paris green cause serious burning of 

 the foliage when mixed with the tobacco extracts. 



EFFECT OF GRAPE LEAFHOPPER CONTROL ON QUALITY OF FRUIT 



As mentioned in foregoing paragraphs dealing with results secured 

 in these spraying experiments with tobacco extracts, it was observed 

 that in every case where the nymphs were successfully controlled the 

 berries of the grape clusters from these vines were much larger, a 

 darker purple in color, and much sweeter than the fruit from un- 

 sprayed vines in the same vineyard. In order to ascertain if there 

 was any marked difference in the sugar content of the grapes from 

 vines growing in the sprayed and unsprayed plats samples represent- 

 ing the average condition of the fruit from sprayed and unsprayed 

 vines from experimental plats in the vineyards of Mr. J. E. Beatty 

 and Mr. W. E. Gray, North East, Pa., were submitted for analysis. 



These samples of grapes taken for analysis were forwarded to Prof. 

 Wm, B. Alwood, in charge of Enological Investigations at the labora- 

 tory of the Bureau of Chemistry located at Sandusky, Ohio. The 

 samples were there analyzed in connection with the extended studies 

 that Prof. Alwood is making of the chemistry of many varieties 

 of grapes grown in the eastern United States in relation to wine 

 production. 



The report received from Prof. Alwood on these samples of grapes 

 from these sprayed and unsprayed experimental plats is given in 

 Table I. 



