The Effect of Leaf-Hopper in jury on the Sugar-content of Grapes

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The grape leaf-hopper, Erythroneura comes Say, is a major pest in the vineyards of the Pennsylvania grape belt along Lake Erie. During seasons of high leaf-hopper infestation, the grapes do not ripen properly. This condition seriously reduces the market value of the grapes for table use and for the manufacture of juice. The extension department of Pennsylvania State College is furnishing a spray service to the grape growers for the control of vineyard insects and diseases under the direction of the author. The effect of a nicotine spray on the leaf-hopper, under the high leafhopper infestation found during the season 1922, was determined by a comparison of the sugar-content of grapes (as indicated by the Brix spindle) that received the nicotine spray with grapes that were not sprayed. The conclusion is that, in a season of severe leaf-hopper infestation, a nicotine spray applied to the vines during the period when the maximum number of nymphs of the first generation of leafhopper are present, will permit the production of grapes of table quality. The work also demonstrates that the sugar-content of the grape juice, under conditions of high leaf-hopper infestation, is an index to the efficiency of the control measure.

Document Type: Research Article

Publication date: August 1, 1923

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